PROCESS TO PRODUCE (1r,4r)-4-SUBSTITUTED CYCLOHEXANE-1-AMINES

AU2022347282B2Pending Publication Date: 2026-07-30RICHTER GEDEON NYRT +1
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Patent Information

Authority / Receiving Office
AU · AU
Patent Type
Applications
Current Assignee / Owner
RICHTER GEDEON NYRT
Filing Date
2022-09-14
Publication Date
2026-07-30

AI Technical Summary

Technical Problem

Current methods for resolving diastereomeric mixtures of 4-substituted cyclohexan-1-amines and cyclohexan-1-ones into their respective trans and cis forms are inefficient, requiring multiple steps and resulting in low yields and purity.

Method used

Employing transaminases as biocatalysts, specifically immobilized whole-cell or purified enzymes like Chromobacterium violaceum and Vibrio fluvialis transaminases, in the presence of pyruvate or other amine acceptors, to catalyze dynamic isomerization reactions, converting diastereomeric mixtures into predominantly trans or cis forms with high selectivity and yield.

Benefits of technology

Achieves high conversion rates (>90%) and purity (>99%) of trans or cis products in batch and continuous flow modes, with immobilized transaminases demonstrating stability and efficiency in dynamic isomerization processes.

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Abstract

The invention relates to a process to produce a (1r,4r)-4-substituted cyclohexane-1-amine [further referred as trans-4-substituted cyclohexane-1-amine] of formula (T), starting from a diastereomeric mixture of 4-substituted cyclohexane-1-amines (formula (C) + formula (T)) or any salt of them by using a single transaminase biocatalyst in whole-cell, soluble or immobilized form in the presence of an amine acceptor used in sub-equimolar up to equimolar quantities in batch mode or in continuous-flow mode. In the first aspect of the present invention 2-(trans-4-aminocyclohexyl)acetic acid esters, more preferably a C1-6 alkyl esters, particularly 2-(trans-4-aminocyclohexyl)acetic acid ethyl ester may be produced. In the second aspect of the present invention hydroxyl-protected or protective group-free trans-4-(2-hydroxyethyl)cyclohexan-1-amines, particularly trans-4-(2-hydroxyethyl)cyclohexan-1-amine may be produced. In the third aspect of the present invention protected 2-(trans-4-aminocyclohexyl)acetaldehydes, particularly trans-4-((1,3-dioxolan-2-yl)methyl)cyclohexan-1-amine may be produced.
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Description

The mixture was extracted with ethyl acetate (3x80 mL) and the unified organic phases were extracted with saturated brine (80 mL) and dried over Na2SO4 and concentrated in vacuum. The crude product was purified by silica gel column chromatography (eluent: hexane-EtOAc=4:l) to give (4-alkoxycarbonylmethyl)cyclohexanone (characterized with formula III). Ethyl 2-(4-oxocyclohexyl)acetate (Illb) (nib) According to the general description, reaction of the solution of ethyl 2-(diethoxyphosphoryl)acetate (18.3 ml, 20.7 g, 92.2 mmol) in dry THF (50 mL) and hexane-washed NaH (3.69 g, 154 mmol) in dry THF (40 mL) with 1,4-cyclohexanedione mono ethylene ketal (12.0 g, 76.8 mmol) in dry THF (50 mL) afforded ethyl 2-(1,4-dioxaspiro[4,5]decan-8-ylidene)acetate (16.8 g, 97 % crude yield) as colorless liquid. The reaction of ethyl 2-(1,4-dioxaspiro[4,5]decan-8-ylidene)acetate (16.7 g, 71.0 mmol) and 10% Pd / C (1.67 g) in ethanol (70 mL) under non-pressurized hydrogen atmosphere afforded ethyl 2-(1,4-dioxaspiro[4,5]decan-8-yl)acetate (16.5 g, 98 % crude yield) as colorless oil. Reaction of the ethyl 2-(1,4-dioxaspiro[4,5]decan-8-yl)acetate (15.0 g, 65.7 mmol) in ethanol (150mL) with IN HC1 (150mL) afforded ethyl-2-(4-oxocyclohexyl)acetate (formula Illb, 5.32 g, 42 % purified yield) as a colorless oil. 'H NMR (500 MHz, DMSO-tA) 5h: 4.07 (2H, q, J=7.1Hz, OCffi-CHi), 2.39 (2H, td, J=13 7 Hz, J=5.9Hz, ^CH^, 2.31 (2H, d, J=7.1 Hz, CWCOOEt), 2.21-2.15 (2H+1H, m, 2xC#eq+C / 7ax-CH2COOEt), 1.98-1.92 (2H, m, 2*CHeq), 1.40 (2H, qd, J=12.1 Hz, J=4.3 Hz, 2xC#ax), 1.19 (3H, t, J=7.1 Hz, m-Ofc); 13C NMR (125 MHz, DMSO-A) 5c: 210.4 (CO), 171.9 (CH2-COOEt), 59.7 (OCH2-CH3), 39.8 (CH2), 39.3 (CH2), 32.3 (CH-CH2COOEt), 31.5 (CH2), 14.0 (CH3); ESI-HRMS: M+H=185.11727 (delta=0.3 ppm; C10H17O3). HR-ESI-MS-MS (CID=35%; rel. int. %): 167(60) and 139(100). IR (neat) Umax: 2933, 1710, 1449, 1368, 1345, 1278, 1201, 1150, 1094, 1029, 968, 754, 503 cm' i GC (HP 5 column): Zr= 1.95 min. Isopropyl-2-(4-oxocyclohexyl)acetate (Hid) (Hid) According to the general description, reaction of the isopropyl 2-(diisopropoxyphosphoryl)acetate (25.00 g, 93.3 mmol) with hexane-washed NaH (3.75 g, 156.4 mmol) in dry THF (100 mL) with 1,4-cyclohexanedione mono ethylene ketal (12.2 g, 78.2 mmol) in dry THF (50 mL) afforded isopropyl 2-(1,4-dioxaspiro[4,5]decan-8-ylidene)acetate (17.1 g, 91 % crude yield) as colorless liquid. The reaction of isopropyl 2-(1,4-dioxaspiro[4,5]decan-8-ylidene)acetate (15.00 g, 62.46 mmol) and 10% Pd / C (1.5 g) in isopropanol (220 mL) under non-pressurized hydrogen atmosphere afforded isopropyl-2-(l,4-dioxaspiro[4,5]decan-8-yl)acetate (14.6 g, 97 % crude yield) as colorless oil. Reaction of the isopropyl 2-(1,4-dioxaspiro[4,5]decan-8-yl)acetate (14.00 g, 57.85 mmol) in isopropanol (170 mL) and 1 N HC1 (170 mL) afforded ethyl-2-(4-oxocyclohexyl)acetate (formula Hid, 8.47 g, 74 % purified yield) as a colorless oil. 'H NMR (500 MHz, DMSO-cL) 5h: 4.91 (1H, quint, J=6.3 Hz, C77-(CH3)2), 2.39 (2H, td, J=13.8 Hz, J~6.0 Hz, 2xC#ax), 2.28-2.27 (2H, m, CHiy 2.19-2.14 (1H+2H, m, CH^-CH2COO'Pr, 2xC / / eq), 1.96-1.92 (2H, m, 2xQ / eq), 1.40 (2H, qd, J=13.0 Hz, J=4.1 Hz, 2xC / / ax), 1.19 (6H, d, J=6.3 Hz, 13C NMR (125 MHz, DMSO-^) 5c: 210.4 (CO), 171.4 (COO'Pr), 66.9 (CH-(CH3)2), 39.6 (CH2-COO'Pr), 32.3 (CH-CH2COO'Pr)+CH2), 31.4 (CH2), 21.5 (CH3); HRMS: M+H=199.13276 (delta=-0.6 ppm; CnHi9O3). HR-ESLMS-MS (CID=35%; rel. int. %): 181(5); 171(11); 167(100); 157(62); 153(91) and 139(64); IR (neat) Umax: 2979, 1711, 1449, 1374, 1278, 1203, 1161, 1107, 967 cm'1. GC (HP 5 column): fe= 1.58 min. 24 cis / trans-Diastereomeric mixtures of 4-substituted cyclohexan-l-aminium chlorides (compounds I HC1 + II HC1 or compounds C HC1 + THC1) 4-(2-Methoxy-2-oxoethyl)cyclohexan-l-aminium chloride (compounds la HC1 + IlaHCl) trans (la.HCI) cis (lla.HCI) To a solution of 2-(4-aminocyclohexyl)acetic acid [cis / trans diastereomeric mixture, T HC1 + C HC1 (G= COOH)] (1 g, 6.37 mmol) in methanol (60 mL) was added 5 M hydrochloric acid solution (9.56 mmol, 1.911 mL, 1.5 eq.). The reaction mixture was stirred at room temperature for 30 min (during this time, the initially opalescent solution cleared and TLC analysis (eluant: n-butanol:acetic acid:water=3:l:l; visulizedby 3% ninhydrin in isopropanol; Rfacid=0.62, RfMe ester=0.68) revealed complete conversion. Next, the solvent was removed using a rotary vacuum evaporator and the residue was dried in a vacuum drying chamber to yield the diastereomeric mixture of the desired methyl ester hydrochloride salt (compounds la HC1 + Ila HCl, 1.28 g, 97% yield) as white solid. IR (ATR) Umax: 2934, 2895, 2863, 1732, 1610, 1507, 1458, 1437, 1365, 1295, 1226, 1168, 1132, 1018 cm'1. (Is,4^)-4-(2-Methoxy-2-oxoethyl)cyclohexan-l-aminium chloride (c / s-compound Ila HCl) 'H NMR (500 MHz, DMSO-^) 8h: 8.12 (3H, br, N^L), 3.58 (3H, s, OC / L), 3.29 (1H, m, C / Lkv-NHL), 2.33 (2H, d, J=7.5 Hz, C^COOMe), 1.95 (1H, m, C#eq-CH>COOMe), 1.811.74 (2H, m, 2*CH), 1.70-1.58 (4H, m, 4*07), 1.46-1.35 (2H, m, 2*CH). 13C NMR (125 MHz, DMSO-A) 5c: 176.39 (COO), 52.14 (OCH3), 48.53 (NCH), 38.15 (CH2), 30.65 (CH), 26.23 (2*CH2), 26.06 (2*CH2). (lr,4r)-4-(2-Methoxy-2-oxoethyl)cyclohexan-l-aminium chloride (Zrans-compound laHCl) 'H NMR (500 MHz, DMSO-^) 5h: 8.12 (3H, br, Wf / 3.59 (3H, s, OC / L), 3.04 (1H, m, C / L-NHf), 2.21 (2H, d, J=7.6 Hz, C^COOMe), 1.98-1.86 (2H, m, 2*CH^, 1.75 (1H, m, C%x-CH2COOMe), 1.72 (2H, br d, J= 14.0 Hz, CtfeqCHNHC), 1.46-1.35 (2H, m, 1.02 (2H, qd, J= 12 Hz, J= 4 Hz, 2*CH^ 13C NMR (125 MHz, DMSO<fc) 5c: 176.43 (COO), 52.09 (OCH3), 48.87 (NCH), 40.48 (CH2), 33.01 (CH), 29.89 (2xCH2), 29.85 (2xCH2), 4-(2-Ethoxy-2-oxoethyl)cyclohexan-l-aminium chloride (compounds Ib HCl + lib HC1) trans                                                   cis (Ib.HCI)                                       (Ilb.HCI) Reaction of ethyl 2-(4-oxocyclohexyl)acetate (Illb, 1.50 g, 8.14 mmol) and 10% Pd / C (0.15 g) with ammonium formate (3.08 g, 48.8 mmol) in ethanol (40 mL) afforded the diastereomeric mixture of 4-(2-ethoxy-2-oxoethyl)cyclohexan-l-amine (compounds lb + lib, 1.24 g, 83% yield, cis / trans= 2.30:1.00 ('H-NMR) ) as colorless oil. Lastly after the introducing of HCl-gas 4-(2-ethoxy-2-oxoethyl)cyclohexan-l-aminium chloride (compounds Ib HCl + Ilb HCl, 1.30 g, 72 % yield) was formed as white solid. (15,4^)-4-(2-Ethoxy-2-oxoethyl)cyclohexan-l-aminium chloride (cz'5-compound Ilb HCl) 'H NMR (500 MHz, DMSO-^) 5h: 8.14 (3H, br, N77C), 4.09-4.02 (2H, m, OC / L), 3.18-3.09 (1H, m, CCax-NHL), 2.27 (2H, d, J=7.5 Hz, C / CCOOEt), 1.98-1.86 (1H, m, CH^-CH2COOEt), 1.69-1.62 (4H, m, 4xCH), 1.53-1.43 (4H, m, 4xCH), 1.18 (3H, t, J=7.2 Hz, Oft), 13C NMR (125 MHz, DMSO-^) 5c: 171.96 (CO), 59.62 (OCH2), 47.2 (CH-N / ZC), 37.92 (CH2COOEt), 30.58 (CHax-CH2COOEt), 25.96 (CH2), 25.89 (CH2), 14.04 (CH3); (lr,4r)-4-(2-Ethoxy-2-oxoethyl)cyclohexan-l-aminium chloride (trans-compound Ib HCl) 'H NMR (500 MHz, DMSO-^) 5h: 8.14 (3H, br, N77C), 4.09-4.02 (2H, m, OCHi), 2.94-2.82 (1H, m, CLC-NHC), 2.18 (2H, d, J=7.6 Hz, C / CCOOEt), 1.98-1.86 (2xH, m, 2x0^), 1.72 (2H, br d, J=14.0 Hz, C%qCHNH3+), 1.64-1.55 (1H, m, C77ax-CH2COOEt), 1.34 (2H, qd, J=12.4 Hz, J=3.1 Hz, 2xCHax), 1.18 (3H, t, J=7.2 Hz, C#3), 1.03 (2H, qd, J=12.7 Hz, J=3.5 Hz, 2xCHax) 13C NMR (125 MHz, DMSO-A) 5c: 171.8 (CO), 59.6 (OCH2), 48.9 (CH-N / / 3% 40.3 (CH2COOEt), 33.1 (CHax-CH2COOEt), 29.8 (CH2), 29.75 (CH2), 14.0 (CH3); HRMS: M+H=186.14853 (delta=-1.8 ppm; CioH2o02N). HR-ESI-MS-MS (CID=35%; rel. int. %): 169(100); 141(2); 140(2); 123(9); 95(15) and 81(6); IR (neat) Umax: 2933,2552, 2037, 1731, 1604, 1509, 1451, 1370, 1291, 1177, 1033 cm'1. 4-(2-Isopropoxy-2-oxoethyl)cyclohexan-l-aminium chloride (compounds Id HC1 + Hd HCl) Reaction of isopropyl 2-(4-oxocyclohexyl)acetate (Hid, 2.00 g, 10.1 mmol) and 10% Pd / C (0.20 g) with ammonium formate (3.82 g, 60.5 mmol) in isopropanol (40 mL) afforded the diastereomeric mixture of 4-(2-isopropoxy-2-oxoethyl)cyclohexan-l-amine (compounds Id + Ild, 1.71 g, 85% yield, cis / trans= 1.07:1.00 (XH-NMR)) as colorless oil. Lastly after the introducing of HCl-gas 4-(2-isopropoxy-2-oxoethyl)cyclohexan-l-aminium chloride (compounds Id HC1 + lid HC1, 1.75 g, 73 % yield) was formed as white solid. (ls,4s)-4-(2-Isopropoxy-2-oxoethyl)cyclohexan-l-aminium chloride (cis-compound Id HCl) 'H NMR (500 MHz, DMSO-^) 5h: 8.10 (3H, br, NZ73+), 4.89 (1H, quint, J=6.25 Hz, CH-(CH3)2), 3.13 (1H, quint, J=5.6 Hz, CT / eq-NT / C), 2.21 (2H, d, J=7.55 Hz, C / 72-COO'Pr), 1.951.89 (1H, m, C#ax-CH2COOTr), 1.67-1.64 (4H, m, 4xC77), 1.53-1.43 (4H, m, 4xC77), 1.18 (6H, d, J=1.71 Hz, 2xCH3), 13C NMR (125 MHz, DMSO-A) 5c: 171. 5 (CO); 66.9 (CH-(CH3)2); 47.3 (CH-NH3+), 38.2 (CH2-COO'Pr), 30.6 (CH-CH2COO'Pr), 26.0 (CH2),25.9 (CH2), 21.5 (CH3). (lr,4r)-4-(2-Isopropoxy-2-oxoethyl)cyclohexan-l-aminium chloride ( / / zw / .s-compound Id HC1) 'H NMR (500 MHz, DMSO-^) 5h: 8.10 (3H, br, 4.88 (1H, quint, J=6.25 Hz, CH-(CH3)2), 2.88 (1H, tt, J=11.8 Hz, J=3.9 Hz, CHaX-W3+), 2.14 (2H, d, J=6.96 Hz, CH2-COO'Pr), 1.95-1.89 (2H, m 2*CHe?), 1.73-1.70 (2H, m, 2*CH), 1.62-1.55 (1H, C / / ax-CH2COO'Pr), 1.33 (2H, qd, J=12.7 Hz, J=3.2 Hz, 2xC#ax), 1.17 (6H, d, J=1.75 Hz, 2*CH3), 1.02 (2H, qd, J=12.8 Hz, J=3.2 Hz, 2*C77); 13C NMR (125 MHz, DMSO-^) 5c: 171.3 (CO); 66.9 (CH-(CH3)2); 48.9 (CH-NHC), 40.6 (CH2-COO'Pr), 33.2 (CH- CH2COO'Pr), 29.8 (CH2), 29.7 (CH2), 21.5 (CH3); HRMS: M+H-200.16423 (delta=-1.4 ppm; CnH22O2N). HR-ESI-MS-MS (CID=35%; rel. int. %): 183(5); 158(5); 141(100); 140(4); 123(6) and 81(8). IR (neat) Umax: 2944, 2627, 2553, 2056, 1729, 1607, 1510, 1458, 1391, 1297, 1182, 1107 cm' 2-(4-Aminocyclohexyl)ethcm-l-ol (compounds IVa + Va) trans                                                    cis (IVa)                                        (Va) Into a round-bottomed flask were added NaBH i (173 mg, 4.5 mmol), tetrahydrofurane (THF, 15 mL) and cA / Zraz?s-2-(4-aminocyclohexyl)acetic acid hydrochloride [T HC1 + C HC1 (G= COOH)] (300 mg, 1.91 mmol). To this mixture, a solution prepared from iodine (483 mg, 1.91 mmol) and THF (4.5 mL) was added dropwise at 0 °C (resulting in exothermic reaction with gas evolution) and the forming mixture was stirred under reflux for 24 h. After cooling to 0 °C, methanol (8 mL) was added dropwise (resulting in heat and gas evolution and dissolving the formed white suspension). After evaporation of the solvent under vacuum, the residual crude product was purified by preparative thin layer chromatography (silica gel, dichloromethane:methanol=20:l as eluant) to yield the diastereomeric mixture of alcohol IVa + Va (173.2 mg 63.6%, cis / trans -46:54) as white powdery solid. Melting point: 92 °C 'H NMR (500 MHz, DMSO-^) 5h: 3.54 (2H, t, J = 5.4 Hz, OCTA), 2.67 and 2.41 (1H, m, C / / -N), 2.00 (1H, m); 1.71 (1H, m); 1.60-1.25 (6H, m); 1.25-1.15 (1H, m); 1.08 (1H, q); 0.89 (1H, q). 13C NMR (125 MHz, DMSO-A) 5c: 62.31 and 62.19 (OCH2), 58.67 and 56.46 (CHN), 40.69 (CHCH2), 35.37 (CH), 33.55 and 33.40 (2xCH2), 29.49 and 29.10 (2xCH2). IR(ATR) Umax: 3483, 3455, 3259, 3227, 3141, 2925, 2888, 2877, 2856, 1598, 1454, 1445, 1356, 1327, 1164, 1050, 874 cm'1. 4-(2-acetoxyethyl)cyclohexan-l-aminium chloride [compounds IV (R= Ac) + V (R= Ac)] tert-butyl A-[4-(2-acetoxyethyl)cyclohexyl]carbamate To a solution of tert-butyl A-[4-(2-hydroxyethyl)cyclohexyl]carbamate [Wu Y.-J., et al (WO2018081384 Al (2018)] (0 4 g, 1.64 mmol), triethylamine (0.4 mL) and 4-dimethylaminopyridine (24 mg) in di chloromethane (15 mL), acetyl chloride (0.175 mL, 2.46 mmol) was added dropwise at 0 °C, then the resulting mixture was stirred at room temperature for 4 h. After evaporation of the volatiles in vacuum, the residue was purified on a silica gel column using dichloromethane:methanol 20:1 eluent to yield the title product [compounds IV (R= Ac) + V (R= Ac)] (0.39 g, 83%) as a substance that crystallizes in a refrigerator. 'H NMR (500 MHz, CDCh) 5h: 4.57 and 4.3 (1H, br, W), 4.0 (2H, q, J= 6.5Hz, OC / L), 3.64 and 3.28 (1H, br C / 7N), 1.97 (3H, s, COC / C), 1.9 (1H, d, J= 10Hz), 1.7 (1H, d, J= 11Hz), 1.6-1.4 (5H, m), 1.38 (9H, s, 3xCYC), 1.3-1.1 (2H, m), 1.05-0.9 (2H, m). 13C NMR (125 MHz, CDCh) 5c: 171.25 (COCH3), 155.27 (CONH), 79.12 (Q, 62.66 (OCH2), 49.87 and 46.52 (CHNH), 35.38 and 33.8 (CH2), 33.3 (CH2), 34.09 and 32.57 (CH), 31.69 (CH2), 29.59 (CH2), 28.44 (3xCH3), 27.71 (CH2), 21.02 (COCH3). 4-(2-acetoxyethyl)cyclohexan-l-aminium chloride [compounds IV (R= Ac) HCl + V (R= Ac)HCl] To the solution of terLbutyl / V-[4-(2-acetoxyethyl)cyclohexyl]carbamate (0.39 g) in ethyl acetate (3.5 mL) was added a 20% solution of hydrochloric acid in ethyl acetate (2.4 mL), and the resulting mixture was stirred at room temperature for 2.5 h. Evaporation of the solvent under vacuum resulted in the title compounds (0.30 g, 100%). 'H NMR (500 MHz, CDCh) 8h: 8.33 and 4.60-4.10 (3H, br, NBL), 4.1 (2H, q, J= 6.5 Hz, OCB2), 3.47 and 3.12 (1H, br, CBN), 2.20 (1H, d, J= 11.5 Hz), 2.06 and 2.05 (3H, s, COCH3), 2.00-1.93 (1H, m), 1.88 (1H, d, J= 13 Hz), 1.85-1.75 (1H, m), 1.72-1.5 (5H, m), 1.5-1.2 (1H, m), 1.03 (1H, q, J= 13 Hz). 13C NMR (125 MHz, CDCh) 8c: 171.22 (COCH3), 62.40 and 62.21 (OCH2), 50.95 and 48.73 (HNH), 35.06 (CH2), 32.91 (CH2), 33.26 and 31.50 (CH), 30.71 (CH2), 30.68 (CH2), 27.45 (CH2), 26.42 (CH2), 21.01 (COCH3). 4-((1,3-Dioxolan-2-yl)methyl)cyclohexan-l-amine (compounds Vila + Villa) trans                                                   cis (Vila)                                             (Villa) tert-Butyl (4-(2-oxoethyl)cyclohexyl)carbamate To a solution of tert-butyl [4-(2-hydroxyethyl)cyclohexyl]carbamate (0.2 g, 0.823 mmol) in dry di chloromethane (7 mL) was added pyridinium chlorochromate (PCC, 1.3 g) portionwise and the resulting mixture was stirred at room temperature for 1 h. The solvent was evaporated from the mixture under vacuum and the resudue was purifid by chromatography on silica gel column with dichloromethane to result the title compound (1.12 g, 58 %) as a viscous oil that crystallized in the refrigerator. 'H NMR (300 MHz, CDCh) 8h: 9.76 (1H, s, CHO), 4.64 and 4.4 (1H, br, NH), 3.72 and 3.36 (1H, br CBN), 2.43-2.3 (2H, dd, CB2), 2.1-1.7 (2H, m), 1.71-1.55 (3H, m); 1.45 (9H, s, 3xCB3), 1.0-1.35 (4H, m). 13C NMR (75 MHz, CDCh) 8c: 202.2 (CHO), 155.4 (CONH), 79.2 (C-O), 50.7 and 49.6 (CHNH), 39.7 and 38.4 (CH2), 33.2 (CH2), 31.7 (CH2), 30.5 (CH), 29.5 (CH2), 28.45 (3xCH3), 27.8 (CH2). terLButyl (4-((1,3-dioxolan-2-yl)methyl)cyclohexyl)carbamate [according to Bush-Petersen J., et al WO 2006050292A2 (2006)] To a solution of tert-butyl (4-(2-oxoethyl)cyclohexyl)carbamate (0.61 g, 2.71 mmol) in acetonitrile (11.5 mL) were added oxalic acid-2H2O (33 mg), MgSOr (0.5 g) and ethylene glycol (0.61 mL) and the mixture was stirred at room temperature for 18 h. After filtering the reaction mixture, the filtrate was diluted with ethyl acetate (40 mL) and washed with saturated NaHCO3 solution (8 mL), water (8 mL) and brine (8 mL). After drying the organic phase over Na2SOr, the solvent was evaporated in vacuo to leave the title compound (0.59 g, 74%) as a heavy oil that crystallized in refrigerator (the sample contained -10% of terLbutyl [4-(2-hydroxyethyl)cyclohexyl]carbamate as impurity). 'H NMR (500 MHz, CDCh) 8h: 4.9 (1H, t, O-CH-O), 4.64 and 4.36 (1H, br, NL / ), 4.0-3.8 (4H, m, 2xC#2), 3.70 and 3.36 (1H, br C / 7N), 2.1-1.8 (2H, m), 1.71-1.5 (5H, m), 1.45 (9H, s, 3xC#3), 1.35-1.2 (2H, m), 1.0-1.2 (2H, m), 13C NMR (125 MHz, CDCh) 8c: 155.4 (O=CNH), 103.6 and 103.4 (O-CH-O), 79.1 (C-O), 64.8 (2xOCH2), 49.8 and 46.5 (CHNH), 40.7 and 33.3 (CH2), 33.4 (CH2), 32.1 (CH2), 39.5 and 32.0 (CH), 29.7 (CH2), 28.46 (3xCH3), 28.2 (CH2). 4-((1,3-Dioxolan-2-yl)methyl)cyclohexan-l-amine (compounds Vila + Villa) [according to Bush-Petersen J., et al WO 2006050292A2 (2006)] To a solution of tert-butyl (4-((l,3-dioxolan-2-yl)methyl)cyclohexyl)carbamate (0.57 g, 2.14 mmol) in ethyl acetate (5 mL) was added a 20% solution of hydrochloric acid in ethyl acetate (3.5 mL), and the resulting mixture was stirred at room temperature for 2 h. After evaporating the solvent under vacuum, the residual solid was dried in a vacuum chamber to give (0.45 g, 100%) as a solid powder. (This sample contained 28% of free aldehyde.) The solid was dissolved in ethylene glycol (0.52 mL) and the mixture was stirred at 40 °C for 8 h under reduced pressure (5 Hgmm). After diluting with ethyl acetate (40 mL), solid Na2CO3 (0.45 g) was added and the resulting mixture was stirred for a few minutes. After filtration, the organic phase was washed with water (2x 10 mL) and brine (10 mL). After drying the organic phase over Na2SO4, the solvent was evaporated in vacuo to leave the title compound (0.16 g, 38%) as a viscous oil (the sample contained -7% of 2-(4-aminocyclohexyl)ethanal and -9% of 2-(4-aminocyclohexyl)ethan-l-ol as impurity). The unified aqueous phases were extracted with dicloromethane (3 x 20 mL) and the resulting organic phase was dried over Na2SO4 and concentrated in vacuum to yield the title compound (23 mg, 6%) as a viscous oil (the sample contained -1.5% of 2-(4-aminocyclohexyl)ethanal and -5.5% of 2-(4-aminocyclohexyl)ethan-l-ol as impurity). 'H NMR (500 MHz, CDCh) 8h: 4.91 (1H, m, OCHO), 3.97 (2H, m, 2*OCH), 3.84 (2H, m, 2*OCH), 2.98 and 2.63 (1H, br, C / / N), 2.19 (2H, br, N / C). 1.91-1.79 (2H, m), 1.72-1.41 (5H, m), 1.35-1.21 (2H, m), 1.01-1.20 (2H, m). 13C NMR (125 MHz, CDCh) 8c: 103.71 and 103.47 (OCHO), 64.69 (2xQCH2), 50.56 (CHNH), 40.82 (CH2), 33.23 (2xCH2), 32.2 (2xCH2), 31.99 (CH). 4-((I,3-Dioxan-2-yl)methyl)cyclohexan-l-amine [compounds VII (n= 2) + VIII (n= 2)] trans                                                    cis VII (n= 2)                                      VIII (n= 2) tert-Butyl (4-((1,3-dioxan-2-yl)methyl)cyclohexyl)carbamate To a solution of tert-butyl (4-(2-oxoethyl)cyclohexyl)carbamate (0.82 g, 3.4 mmol) in acetonitrile (15.5 mL) were added oxalic acid (44.4 mg), MgSO4 (0.6 g) and propylene glycol (1.1 mL) and the mixture was stirred at room temperature for 18 h. After filtration, the filtrate was diluted with ethyl acetate (54 mL) and washed with saturated NaHCOs solution (11 mL), water (11 mL) and brine (22 mL). After drying the organic phase over Na2SO4, the solvent was evaporated in vacuo. The residue was purified on a silica gel column using dichloromethane:methanol 20:1 eluent to leave the title compound (0.93 g, 99%) as a heavy oil that crystallized in refrigerator (the sample contained -10% of terLbutyl [4-(2-hydroxyethyl)cyclohexyl]carbamate as impurity). 'H NMR (500 MHz, CDCh) 8h: 4.64 and 4.37 (1H, br, N / 7), 4.58 (1H, t, OCHO), 4.21-4.01 (2H, dd, J= 4.5 Hz and 11.5 Hz, CHi), 3.76 (2H, t, J= 12.5 Hz), 3.71 and 3.36 (1H, br, C77N), 2.14-1.90 (2H, m), 1.79 (1H, d,J=HHz), 1.71-1.51 (5H, m), 1.51-1.46 (1H, m), 1.45 (9H, s, 3xCft), 1.35 (1H, d, J= 13.5 Hz), 1.29-1.15 (1H, m), 1.15-1.01 (2H, m). 13C NMR (125 MHz, CDCh) 5c: 155.28 (CONH), 101.05 and 100.92 (OCHO), 79.04 (C), 66.92 (2*OCH2), 53.42 and 51.43 (CHNH), 42.04 and 32.37 (CH2), 33.34 (CH2), 33.13 and 31.60 (CH), 32.00 (CH2), 29.61 (CH2), 28.45 (3*CH3), 28.13 (CH2), 25.83 (CH2). 4-((1,3-Dioxan-2-yl)methyl)cyclohexan-l-amine (compounds VII+VIII (n= 2)) To a solution of tert-butyl (4-((1,3-dioxan-2-yl)methyl)cyclohexyl)carbamate (0.65 g, 2.18 mmol) in ethyl acetate (5.5 mL) was added a 20% solution of hydrochloric acid in ethyl acetate (4 mL), and the resulting mixture was stirred at room temperature for 1 h. After evaporating the solvent under vacuum, the residual solid was dried in a vacuum chamber to give (0,53 g, 100%) as a solid powder. (The sample contained 10% of free aldehyde.) The solid was dissolved in propylene glycol (0.6 mL) and the mixture was stirred at 40 °C for 8 h under reduced pressure (5 Hgmm). To the mixture diluted with ethyl acetate (40 mL) Na2CO3 (0.38 g) was added and the suspension was stirred for a few minutes. After filtration, the organic phase was washed with water (2x10 mL) and brine (10 mL). After drying the organic phase over Na2SO4, the solvent was evaporated in vacuo to leave the title compound (0.28 g, 60%) as a viscous oil (the sample contained -12.5% of 2-(4-aminocyclohexyl)ethan-l-ol as impurity). The unified aqueous phases were extracted with dicloromethane (3 x20 mL) and the resulting organic phase was dried over Na2SO4 and concentrated in vacuum to yield the title compound (0.18 g, 40%) as a viscous oil (the sample contained -7% of 2-(4-aminocyclohexyl)ethan-l-ol as impurity). 'H NMR (500 MHz, CDCh) 5h: 4.77 (1H, m, OC / / O), 4.10 (2H, m, 2xOC77), 3.82 (2H, m, 2*007), 2.98 and 2.63 (1H, br, C77N), 2.42 (2H, br, N772), 1.91-1.80 (2H, m), 1.72-1.41 (7H, m), 1.40-1.31 (2H, m), 1.20-1.07 ((1H, m), 1.05-0.95 (1H, m). 13C NMR (125 MHz, CDCh) 5c: 101.21 and 101.01 (OCHO), 66.89 (2*OCH2), 50.61 (CHNH), 42.16 (CH2), 34.11 (2*CH2), 32.06 (2xCH2), 31.71 (CH), 25.82 and 25.68 (OCH2CH2CH2O). 4-Methylcyclohexan-l-aminium chloride (compounds T HC1 + C HC1 (G= H)) 0 Cl trans T.HCI (G= H) 0 Cl cis C.HCI (G=H) Reaction of 4-methylcyclohexane-l-one (K (G= H)) (5.5 ml, 5.00 g, 44.6 mmol) and 10% Pd / C (0.50 g) with ammonium formate (16.86 g, 267.5 mmol) in methanol (100 ml) afforded 4-methylcyclohexan-1 -amine (compounds T + C (G= H)) (3.78 g, 75 %yield) as colorless liquid. Lastly after the introducing of HCl-gas 4-methylcyclohexan-l-aminium chloride (compounds T HC1 + C HC1 (G= H)) (2.83 g, 43% yield, cis :trans=\MA.23 (XH-NMR)) was formed as white solid. (l.s,4.s)-4-Methyl cyclohexan-1 -aminium chloride (czs-compound CHC1 (G= H)) 'H NMR (500 MHz, DMSO-^) 5h: 8.12 (3H, br, N#3+), 3.11 (1H, tt, J=6.8 Hz, J=3.9 Hz, CH^H^X 1.69-1.65 (2H, m, 2*CHX 1.64-1.61 (2H, m, 2*CHX 1.61-1.59 (H, m, C / 7-CH3), 1.49-1.44 (2H, m, 2xCJ7), 1.42-1.35 (2H, m, 2xC#-CH3), 0.90 (3H, t, J=6.8 Hz, Cft); 13C NMR (125 MHz, DMSO-A) 5c: 47.4 (CH-NH3+), 28.2 (CH-CH3), 28.1 (CH2-CHCH3), 26.1 (CH2), 19.5 (CH3); (lr,4r)-4-Methylcyclohexan-l-aminium chloride (Zraws-compound T HC1 (G= H)) 'H NMR (500 MHz, DMSO-^) 5h: 8.12 (3H, br, Wf), 2.86 (1H, tt, J=11.8 Hz, J=4.0 Hz, CH^H^X 1.93-1.91 (2H, m, 2*CHeqX 1.69-1.65 (2H, m, 2*CHeqX 1.32 (2H, qd, 1=12.7 Hz, J=3.3 Hz, 2^^^, 1.26-1.22 (1H, m, C / 7^CH3), 0.94 (2H, qd, J=13.1 Hz, J=3.1 Hz, 2xCH^), 0.85 (3H, t, J=6.5 Hz, C#3); 13C NMR (125 MHz, DMSO-6L) 5c: 49.1 (CH-NH3+), 32.3 (CH2-CHCH3), 30.9 (CH-CH3), 30.1 (CH2), 21.8 (CH3); IR (liquid film) vmax:2927, 2563, 2049, 161, 1512, 1455, 1392, 1127, 1029 cm'1. HRMS: M+H=l 14.12744 (delta=-2.5 ppm; C7H16N). HR-ESI-MS-MS (CID=35%; rel. int. %): 97(100). 4-Ethylcyclohexan-l-aminium chloride (compounds T HC1 + C HC1 (G= Me)) trans T.HCI (G= Et) e ci cis C.HCI (G= Et) Reaction of 4-ethylcyclohexane-l-one (K (G= Me)) (5.6 ml, 5.00 g, 39.6 mmol) and 10% Pd / C (0.500 g) with ammonium formate (15.00 g, 237.7 mmol) in methanol (100 ml) afforded 4-ethylcyclohexan-1-amine (compounds T + C (G= Et)) (4.26 g, 85 %yield, cis :trans=l.93:1.00 ('H-NMR)) as colorless liquid. Lastly after the introducing of HCl-gas 4-ethylcyclohexan-l-aminium chloride (compounds THC1 + C HC1 (G= Me)) was formed as white solid. (15,45')-4-Ethylcyclohexan-l-aminium chloride (czs-compound C HC1 (G= Me)) 'H NMR (500 MHz, DMSO-^) 5h: 8.15 (3H, br, NZ73+), 3.12 (1H, br m CLLrNL%), 1.681.65 (2H, m, 2*C77), 1.64-1.60 (2H, m, 2*C / / ), 1.49-1.45 (2H, m, 2xC77), 1.44-1.41 (2H, m, 2xCH), 1.29 (1H, m, C7L-CH2CH3). 1.27 (2H, quint, J=7.2 Hz, C / / 2CH3), 0.85 (3H, t, J=7.3 Hz, CH2C / / 3); 13C NMR (125 MHz, DMSO-A) 5c:47.6 (CH-NJ73+), 35.3 (CH-CH2CH3), 26.2 (CH2), 25.9 (CH2), 25.8 (CH2CH3), 11.3 (CH2CH3). (lr,4r)-4-Ethylcyclohexan-l-aminium chloride ( / ra / M-compound T HC1 (G=Me)) 'H NMR (500 MHz, DMSO-^) 5h: 7.99 (3H, br, N773+), 2.87 (1H, br m CJ7ra-NJ73+), 1.961.95 (2H, m, 2*CHeq), 1.75-1.74 (2H, m, 2xCHeq), 1.31 (2H, qd, J=12.8 Hz, J=3.4 Hz, 2xCHax\ 1.18 (2H, quint, J=15 Hz CW2CH3), 1.07-1.03 (1H, m, C / Lc-C^CHs), 0.91 (2H, qd, J=12.9 Hz, J=3.3 Hz, 2*CHOT), 0.85 (3H, t, J=7.5 Hz, CH2C / / 3); 13C NMR (125 MHz, DMSO-6L) 5c: 49.4 (CH-NH3+), 37.5 (CH-CH2CH3), 30.1 (CH2), 29.9 (CH2-CHCH2CH3), 28.7 (CH2CH3), 11.6 (CH2CH3), IR (liquid film) Umax: 2933,2575,2047, 1583, 1505, 1453, 1388, 1236, 1121, 1036 cm'1. HRMS: M+H=128.14303 (delta=-2.7 ppm; CsHisN). HR-ESI-MS-MS (CID=35%; rel. int. %): 111(100) and 69(9). 4-Phenylcyclohexan-l-aminium chloride (compounds T HC1 + C HC1 (G= Ph)) trans T.HCI (G= Ph) 0 Cl cis C.HCI (G= Ph) Reaction of 4-phenylcyclohexane-l-one one (K (G= Ph)) (4.00 g, 22.9 mmol) and 10% Pd / C (0.40 g) with ammonium formate (8.66 g, 137.4 mmol) in methanol (80 ml) afforded 4-phenylcyclohexan-1-amine (compounds T + C (G= Ph)) (2.93 g, 73 %yield, cis / trans= 1.00:3.70) as liquid. Lastly after the introducing of HC1 4-phenylcyclohexan-l-aminium chloride (compounds T HC1 + CHC1 (G= Ph)) (2.2 g, 45 % yield) was formed as white solid. (15,45')-4-Phenylcyclohexan-l-aminium chloride (cA-compound C HC1 (G= Ph)) 'H NMR (500 MHz, DMSO-^) 5h: 8.03 (3H, br, NtfC), 7.34-7.32 (H, m, krHorto), 7.31-7.27 (H, m, MHmeta), 7.19-7.17 (H, m, krHpara\ 3.42-3.41 (1H, m, C^-NH3+), 2.57 (1H, tt, J=11.4 Hz, J=3.4 Hz, CT / ^-Ph), 13C NMR (126 MHz, DMSO<fc) 5c: 146.2 (ArC), 128.2 (ArCHmeta), 126.9 (ArCFLm), 125.9 (ArCH^™), 45.8 (CH-NH3+), 41.7 (CH-Ph), 27.8 (CH2); 26.6 (CH2); (lr,4r)-4-Phenylcyclohexan-l-aminium chloride (trans-compound T HC1 (G= Ph)) 'H NMR (500 MHz, DMSO-^) 5h: 8.03 (3H, br, NT / L), 7.31-7.27 (H, m, Ar / 7^), 7.24-7.23 (H, m, krHorto\ 7.19-7.17 (H, m, kiHPara\ 3.06 (1H, tt, J=11.6Hz, J=3.9Hz, CHax-NH3+), 2.47 (1H, tt, J=12.0 Hz, J=3.4 Hz, C / iC-Ph), 13C NMR (126 MHz, DMSO-^) 5c: 146.0 (ArC), 128.2 (ArCHmeta), 126.6 (ArCFLm), 126.0 (ArCH^™), 48.9 (CH-NHC), 42.2 (CH-Ph), 31.4 (CH2); 30.4 (CH2), HRMS: M+H- l 76.14302 (delta=-2.0 ppm; Ci2Hi8N). HR-ESI-MS-MS (CID=35%; rel. int. %): 159(100); 91(3) and 81(3); IR (liquid film) Umax: 2939, 2544, 2038, 1610, 1504, 1451, 1390, 1182, 1073, 1020, 758, 700 cm'1. 4-Benzylcyclohexan-l-aminium chloride (compounds T HC1 + C HC1 (G= CH2Ph)) trans                                                    cis T.HCI (G= CH2Ph)                     C.HCI (G= CH2Ph) Reaction of 4-benzylcyclohexyl-l-one (K (G= CH2Ph)) (1.50 g, 7.97 mmol) and 10% Pd / C (0.45 g) with ammonium formate (3.01g, 47.8 mmol) in methanol (60 ml) afforded 4-benzylcyclohexan-1-amine (compounds T + C (G= CH2Ph)) (0.29 g, 19%yield, cis / trans= 1.00:1.08 ^H-NMR)) as liquid. Lastly after the introducing ofHCl-gas 4-benzylcyclohexan-l-aminium chloride (compounds THC1 + C HC1 (G= CH2Ph)) (0.22 g, 12 % yield) was formed as white solid. (ls,4s)-4-Benzylcyclohexan-l-aminium chloride (c / .s-compound C HC1 (G= CH2Ph)) 'H NMR (500 MHz, DMSO-^) 5h: 8.14 (3H, br, Wfp 7.29-7.25 (2H, m, Ar&eta), 7.197.13 (3H, m, ArHpara, ArHorto), 3.14-3.13 (1H, m, CJ7-NH3+), 2.55 (2H, d, J=7.64 Hz, CHi-Ph), 1.78-1.71 (3H, m, 2*CH, Ctfax-OLPh), 1.66-1.59 (2H, m, 2*CH), 1.44-1.41 (4H, m, 4*CH); 13C NMR (125 MHz, DMSO-^) 5c: 140.6 (ArC), 128.7 (ArCorto), 128.1 (ArCmeta), 125.7 (ArC, para), 47.6 (CH-NH3+), 39.3 (CH2-Ph), 35.4 (CH-CH2-Ph), 26.0 (CH2), 25.9 (CH2); (lr,4r)-4-Benzylcyclohexan-l-aminium chloride ( / rara-compound THC1 (G= CH2Ph)) '11 NMR (500 MHz, DMSO-^) 5h: 8.14 (3H, br, N / t%), 7.29-7.25 (2H, m, AxHmeta), 7.197.13 (3H, m, ArHorto, AsHpara), 2.88 (1H, tt, J=11.8 Hz, J=3.2 Hz, CLLx-NH?), 2.45 (2H, d, J=6.9 Hz, C772-Ph), 1.93-1.91 (2H, m, 2*CHeq), 1.66-1.59 (2H, m, 2xQHeq\ 1.44-1.41 (1H, m, CLLx-CH^h), 1.28 (2H, qd, 1=12.61 Hz, J=3.2 Hz, 2*CHax), 1.00 (2H, qd, J=13.58 Hz, J=2.9 Hz, 2 CM,v); 13C NMR (125 MHz, DMSO-^) 5c: 140.3 (ArC), 128.8 (ArCorto), 128.0 (ArCmeta), 125.7 {ArCpara), 49.3 (CH-NHC), 42.3 (CH2-Ph), 37.9 (CH-CH2Ph), 30.0 (CH2), 29.9 (CH2), HRMS: M+H=190.15850 (delta=-2.8 ppm; Ci3H20N). HR-ESI-MS-MS (CID=35%; rel. int. %): 173(100); 117(2); 105(31); 95(9); 91(5) and 81(2). IR (liquid film) Umax: 3073,2610, 2035, 1610, 1511, 1494, 1453, 1392, 1347, 1203, 1062, 744, 701 cm’1. cis-Diastereomer of 2-(4-aminocyclohexyl)acetic acid ethyl ester hydrochloride (compound Hb HC1) (1 s,4s)-4-(2-Ethoxy-2-oxoethyl)cyclohexan-l -aminium chloride (compound lib HC1) cis (Ilb.HCI) The cv.s -di a st ereomer of 2-(4-aminocyclohexyl)acetic acid ethyl ester hydrochloride (IlbHCl with de -90.2%) was obtained from the mother liquor of the recrystallization of the diatereomeric mixture of 2-(4-aminocyclohexyl)acetic acid ethyl ester hydrochloride (Ib HCl lib HC1 in -1:1 ratio) at industrial scale production process according to WO2010 / 070368. (15,4^)-4-(2-Ethoxy-2-oxoethyl)cyclohexan-l-aminium chloride (cA-compound Ilb HCl) 'H NMR (500 MHz, DMSO-^) 5h: 8.14 (3H, br, N / t%), 4.09-4.02 (2H, m, OCft), 3.18-3.09 (1H, m, C / Cx-NHs ), 2.27 (2H, d, J=7.5 Hz, C772COOEt), 1.98-1.86 (1H, m, CH^-CH2COOEt), 1.69-1.62 (4H, m, 4*CH), 1.53-1.43 (4H, m, 4*CH), 1.18 (3H, t, J=7.2 Hz, CHi). 13C NMR (126 MHz, DMSO-^) 5c: 171.96 (CO), 59.62 (OCH2), 47.2 (CH-W), 37.92 (CH2COOEt), 30.58 (CHax-CH2COOEt), 25.96 (CH2), 25.89 (CH2), 14.04 (CH3). IR (neat) Umax: 2927, 1727, 1601, 1520, 1511, 1447, 1375, 1226, 1165, 1031 cm'1. Transaminases of different microbial strains as biocatalysts Generation of plasmids and expression of an (S)-selective transaminase from Chromobacterium violaceum (CvS-TX) was disclosed by K. E. Cassimje et al. (ACS Catal. 1(9), 1051-1055 (2011), DOI: 10.1021 / cs200315h). Recombinant expression of His-tagged Cv5-TA W60C mutant (CvSweoc-TA) exhibiting enhanced catalytic properties was published by K. E. Cassimje etal. (Org. Biomol. Chem., 10, 5466-5470 (2012), DOI: 10.1039 / C2OB25893E). Recombinant expression of His-tagged P / S-TA was unveiled by F. G. Mutti et al. (Eur. J. Org. Chem., 10031007 (2012), DOI: 10.1002 / ejoc.201101476). Production and whole cell immobilization of three (R)- and three (S)-selective TAs, the (7?)-selective TAs from Arthrobacter sp. (ArR-TK\ its mutated variant (ArAmut-TA), Aspergillus terreus (AtR-HAf and the (5)-selective TAs from Arthrobacter citreus (ArA-TA), a mutated variant of Chromobacterium violaceum (CvSweoc-TA), Vibrio fluvialis (F^-TA), respectively, applied for kinetic resolution of racemic amines in immobilized whole-cell form was published by Z. Molnar et al. (Catalysts, 9, 438 (2019), DOI: 10.3390 / catal9050438). A Transaminase Screening Kit (Codexis, Redwood City, USA) containing 24 mutant amine transaminases (ATAs) from two different parent lineages: Vibrio fluvialis JS17 ATA (F / S-TA: Biotechnol. Bioeng. 65, 206-211 (1999), DOI: 10.1002 / (SICI)1097-0290(19991020)65:2<206::AID-BITll>3.0.CO;2-9) and Arthrobacter sp. ATA (ArA-TA: Appl. Microbiol. Biotechnol. 69, 499-505 (2006), DOI: 10.1007 / s00253-005-0002-1) was also assayed. The 17 mutations (marked as bold in SEQ ID NO. 3; see Figure 4) in a variant of F^-TA, named as ATA-217 were disclosed by Novick S. J. et al (ACS Catal. 11, 3762-3770 (2021), DOI: 10.1021 / acscatal.0c05450). Expression of transaminases Production of ArA-TA and F / S-TA was achieved in E. coli BL2KDE3) containing the recombinant pASK-IBA35+ plasmid with the gene of the given TA. LB-Car medium (5 mL; LB medium containing carbenicillin, 50 mg L'1) was inoculated with one fresh colony from an overnight LB-Car agar plate and cells were grown overnight in shake flask (37 °C, at 200 rpm). LB medium (0.5 L) in a 2 L flask was inoculated with seed culture (2 mL) and cells were grown at 37 °C, 200 rpm until the OD640 reached 0.8 (approx. 4 h). For induction, tetracycline solution (20 pL, 5 mg ml’1 tetracycline in ethanol) was added and the culture was shaken for further 16 h at 25 °C, 200 rpm. The cells were then harvested by centrifugation (15,000 g, 4 °C, 20 min). Production of A / A-TA, ArA-TA, ArAmut-TA and CvAweoc-TA was achieved in E. coli BL2KDE3) containing the recombinant pET21a plasmid with the gene of the given TA. LB-Car medium (5 mL; LB medium containing carbenicillin, 50 mg L’1) was inoculated with one fresh colony from an overnight LB-Car agar plate and cells were grown overnight in shake flask (37 °C, at 200 rpm). Autoinduction medium (0.5 L: Na2HPO4, 6gL-1; KH2PO4, 3gL-1; tryptone, 20 g L’1; yeast extract, 5 g L’1; NaCl, 5 g L’1; glycerol, 7.56 g L’1; glucose, 0.5 g L’1; lactose, 2 g L’1 s) in a 2 L flask was inoculated with seed culture (2 mL) and was shaken for 16 h at 25 °C, 200 rpm. The cells were then harvested by centrifugation (15,000 g, 4 °C, 20 min). Immobilization of transaminase-expressing whole-cells The silica sol was prepared as follows: TEOS (14.4 mL) was added to a solution containing 0.1 M HNO3 (1.3 mL) and distilled water (5 mL) and the resulted mixture was sonicated for 5 min at room temperature (Emag Emmi 20HC Ultrasonic Bath, 45 kHz) and kept at 4 °C for 24 h. Then MAT540 support (3 g) was mixed with a cell paste suspension (6 mL; taken from 1 g of centrifuged cell paste resuspended in 6 ml of 0.1 M phosphate buffer, pH 7.5), and the resulted suspension was shaken intensively until become homogeneous (Technokartell Test Tube Shaker Model T3SK, 40 Hz, room temperature, 5 min). Finally, the homogenized supported cell suspension was mixed with the silica sol and the resulted mixture was shaken intensively (Technokartell Test Tube Shaker Model T3SK, 40 Hz, room temperature, 5 min). Gelation occurred within 30 min at room temperature, followed by aging the gel at 4 °C for 48 h in an open dish. The crude immobilized TA biocatalyst was washed with distilled water (2x15 mL, 100 mM, pH 7.5), dried at room temperature (24 h), and stored at 4 °C. Purification of the W60C mutant of transaminase from Chromobacterium violaceum (CvSweoc-TA) After fermentation of K coli cells containing CvSweoc-TA, cells were disrupted by French press, centrifuged and crude cell extract was purified by Ni-NTA resin as described previously by F. G. Mutti et al. (Eur. J. Org. Chern., 1003-1007 (2012), DOI: 10.1002 / ejoc.201101476). Cofactor PLP was added to stock solutions of CvSwsoc-TA which were kept at -20 °C in 20% glycerol solution until further use. Purification of the transaminase from Vibrio fluvialis (VfS-TA) After fermentation of E. coli cells containing VfS-TA, cells were disrupted by French press, centrifuged and crude cell extract was purified by Ni-NTA resin as described above for the purification of CvSwtoc-TA. Cofactor PLP was added to stock solutions of L / S-TA which were kept at -20 °C in 20% glycerol solution until further use. Surface activation of aminoethyl polymethacrylate resins with glycerol diglycidyl ether (GDE) According to the method of E. Abahazi et al. (Biochem. Eng. J. 132, 270-278 (2018), DOI: 10.1016 / j.bej.2018.01.022)), ethyleneamine-functionalized methacrylic polymer resins ReliZyme™ EA403 / S (1.0 g, particle size 150-300 pm, pore size 400-600 A), were added to a glycerol diglycidyl ether solution (10 mmol) in ethanol (15 mL). The suspension of polymer support in bisepoxide solution was shaken at 450 rpm for 24 h at 25 °C. The activated support was filtered off on a glass filter (G3), washed with Patosolv® (3><10 mL), dried at room temperature (4 h) and stored at 4 °C under argon atmosphere. Immobilization of CvSweoc-TA on GDE-activated aminoethyl resins According to the method of E. Abahazi et al. (Biochem. Eng. J. 132, 270-278 (2018), DOI: 10.1016 / j .bej.2018.01.022)), in anEppendorf tube (1.5 mL) purified CvSweoc-TA (210 pL, 4.8 mg mL'1) was diluted with HEPES buffer (790 pL, 50 mM, pH 7.0), and then the GDE-activated aminoethyl resin (10.0 mg, resulting in enzyme:support ratio = 1:10) was added to the solution. The resulted suspension was shaken at 900 rpm for 24 h at 25 °C. The immobilized CvSweoc-TA was centrifuged, washed with HEPES buffer (2x1.0 mL). Protein concentrations of the CvSweoc-TA solution before immobilization and in the supernatant were determined by a NanoDrop 2000 spectrophotometer. Immobilization yield (IY) was calculated according to equation IY(%) = (Po-P) / Pox 100 (where Po [mg mL'1] is the initial protein concentration before immobilization, and P [mg mL'1] is the protein concentration in supernatant after immobilization). Because after immobilization of the purified native CvSweoc-TA onto the GDE-activated aminoethyl resin (EA-G) negligible protein concentration could be detected (P - 0 mg mL'1), immobilization yield at enzyme: support ratio = 1:10 was -100%. After immobilization, the resulted covalently immobilized CvSweoc-TA biocatalyst was used immediately in dynamic isomerization reactions. The immobilization process could be upscaled tenfold in 4 mL vials with identical results. Immobilization ofVjS-TA on GDE-activated aminoethyl resins According to the method of E. Abahazi et al. (Biochem. Eng. J. 132, 270-278 (2018), DOI: 10.1016 / j .bej.2018.01.022)), in an Eppendorf tube (1.5 mL) purified L / V-TA (250 pL, 4.5 mg mL'1) was diluted with HEPES buffer (790 pL, 50 mM, pH 7.0), and then the GDE-activated aminoethyl resin (10.0 mg, resulting in enzyme: support ratio = 1:10) was added to the solution. The resulted suspension was shaken at 900 rpm for 24 h at 25 °C. The ( / .S-TA was centrifuged, washed with HEPES buffer (2XLO mL). Protein concentrations of the F / S-TA solution before immobilization and in the supernatant were determined by a NanoDrop 2000 spectrophotometer. An immobilization yield of —100% at enzyme: support ratio = 1:10 was observed. After immobilization, the resulted covalently immobilized EfS-TA biocatalyst was used immediately in dynamic isomerization reactions. Continuous-flow immobilization of CvSmoc-TA on GDE-activated aminoethyl resins According to the method of E. Abahazi et al. (Biochem. Eng. J. 132, 270-278 (2018), DOI: 10.1016 / j.bej.2018.01.022)), flow-through immobilization of CvSweoc-TA was performed in a laboratory scale flow reactor built from a Knauer Azura P4.1S isocratic HPLC pump attached to CatCart™ columns filled with the EA-G supports in an in-house made aluminum metal block column holder with precise temperature control. CvSWoc-TA solution (2 mg mL'1, in a volume corresponding to enzyme:support ratio 1:10) was recirculated in stainless-steel CatCart™ columns filled with EA-G support (stainless steel, inner diameter: 4 mm; total length: 70 mm; packed length: 65 mm; inner volume: 0.816 mL; support weights: 211.4 ± 16.1 mg) at a flow rate of 0.5 mL min'1. Protein concentrations of the CvSiveoc-TA solution before immobilization and at several time points during immobilization were determined by a Nano-Drop 2000 spectrophotometer. Dynamic isomerization (DI) of trans / cis-diastereomeric mixture of 2-(4-aminocyclohexyl)-acetic acid ethyl esters (compounds Ib+ lib) with a transaminase in batch mode Example 1 DI of trans / cis-ethyl esters (Ib+ lib) with immobilized whole cell CvSweoc-TA in presence of pyruvate in batch mode The immobilized whole cell Chromobacterium violaceum transaminase W60C mutant biocatalyst (Cv5weoc-TA, 50 mg) was suspended in phosphate buffer (1.6 mL, 100 mM, pH 7 5) in a 4 ml vials. The cis / trans diastereomeric mixture of 2-(4-aminocyclohexyl)acetic acid ethyl ester hydrochloride salt [compounds Ilb HCl + Ib HCl, in 44:56 ratio; 11.1 mg, 50 pmol, in phosphate buffer (200 pL, 100 mM, pH 7.5)] and sodium pyruvate as amine acceptor [0.5 eq., 0.23 mg, 25 pmol, in phosphate buffer (200 pL, 100 mM, pH 7.5)] were added to the biocatalyst suspension providing a final reaction volume of 2 mL with 25 mM of cis / trans diastereomeric mixture (lib•HCl / Ib HCl). The reaction mixture was shaken on an orbital shaker (500 rpm) at 30 °C for 24 h. To the samples taken from the reaction mixture (150 pL), sodium hydroxide (100 pL, 1 M) was added, followed by extraction with ethyl acetate (800 pL). Derivatization of the amines was performed by the addition of acetic anhydride (20 pL, 60 °C, 1 h), then the organic phase was dried over Na2SOr. Samples were analyzed by gas chromatography. According to integration of peak areas for the ketone (Illb) and the corresponding acetamides of lb and lib, the molar fractions of the products lb, lib, and Illb were in the mixture 76.3%, 0.6% and 23.0%, respectively. The reaction mixture was centrifuged to remove the biocatalyst. The aqueous supernatant was acidified by addition of aqueous cc. HC1 to pH 1, and it was extracted with dichloromethane (3x3 mL). The unified organic phases were washed with saturated brine (3 mL) and dried over anhydrous NazSOi and concentrated in vacuum to yield the ketone (compound Illb: 2.0 mg, 11 pmol, 95% yield). The pH of the acidified aqueous phase was adjusted pH 10 by addition of 25% aqueous ammonium hydroxide and the basic solution was extracted with dichloromethane (3x3 mL). The unified organic phase was washed with saturated brine (3 mL) and dried over anhydrous NaiSOi and concentrated in vacuum to yield the trans-amine (compound lb: 4.8 mg, 26 pmol, 68% yield with detrans= 98.3% by GC). Example 2 DI of trans / cis-ethyl esters db lib) with immobilized whole cell VfS-TA in presence of pyruvate in batch mode The procedure was performed as presented in Example 1 modified in a way that immobilized whole cell Vibrio fluvialis transaminase (Fj^-TA, 50 mg) biocatalyst was used. After 24 h reaction time, according to integration of peak areas for the ketone (Illb) and the corresponding acetamides of lb and Hb, the molar fractions of the products lb, lib, and Illb were in the mixture 70.6%, 1.5%, 27.9% and respectively. Example 3 DI of trans / cis-ethyl esters (Ib+ lib) with doubled amount of immobilized whole cell VfS-TA in presence of pyruvate in batch mode The procedure was performed as presented in Example 1 modified in a way that immobilized whole cell Vibrio fluvialis transaminase (FyS-TA, 100 mg) biocatalyst was used. After 6 h reaction time, according to integration of peak areas for the ketone (Illb) and the corresponding acetamides of lb and lib, the molar fractions of the products lb, lib, and Illb were in the mixture 74.5%, 1.0% and 24.5%, respectively. Example 4 5   DI of trans / cis-ethyl esters (Ib+ lib) with purified soluble CvSweoc-TA in presence of pyruvate in batch mode The procedure was performed as presented in Example 1 modified in a way that Ni-NTA-purified Chromobacterium violaceum transaminase W60C mutant (CvSweoc-TA) biocatalyst in solution was used (at 0.5 mg / ml protein concentration in the final reaction mixture, 10 supplemented with 0.2 mM piridoxal-5-phosphate (PLP)) in the reaction starting from 25 mM of cis / trans diastereomeric mixture (lib HCl / Ib HCl= 44:56). After 2 h reaction time, according to integration of peak areas for the ketone (Illb) and the corresponding acetamides of lb and lib, the molar fractions of the products lb, lib, and Illb were in the mixture 86.0%, 0% and 14.0%, respectively. 15 Extractive workup as presented in Example 1 gave ketone (compound nib: 1.3 mg, 7 pmol, -98% yield) Zra«s-amine (compound lb: 4.9 mg, 27 pmol, 62% yield with detrans >99% by GC). Example 5 DI of trans / cis-ethyl esters (Ib+ lib) with purified soluble VfS-TA in presence of pyruvate in batch mode 20 The procedure was performed as presented in Example 1 modified in a way that Ni-NTA-purified Vibrio fluvialis transaminase (E / S-TA) biocatalyst was used (at 0.5 mg / ml protein concentration in the final reaction mixture, supplemented with 0.2 mM piridoxal-5-phosphate (PLP)) in the reaction starting from 25 mM of cis / trans diastereomeric mixture (lib HCl / Ib HC1= 51:49). 25 After 3 h reaction time, according to integration of peak areas for the ketone (Illb) and the corresponding acetamides of lb and lib, the molar fractions of the products lb, lib, and Illb in the mixture were 79.0%, 0.5% and 20.5%, respectively. Extractive workup as presented in Example 1 gave ketone (compound Illb: 1.7 mg, -9 pmol, -92% yield) / raws-amine (compound lb: 4.8 mg, 26 pmol, 65% yield with detrans= 98.7% by GC). Example 6 DI of trans / cis-ethyl esters (Ib+ lib) with VfS-TA covalently immobilized on porous resin in presence of pyruvate in batch mode The procedure was performed as presented in Example 1 modified in a way that covalently immobilized Vibriofluvialis transaminase on polymer resin (F / S'-TA, 10 mg) as biocatalyst was used. After 6 h reaction time, according to integration of peak areas for the ketone (Illb) and the corresponding acetamides of lb and lib, the molar fractions of the products lb, lib, and Illb in the mixture were 74.9%, 1.6% and 23.6%, respectively. Example 7 DI of trans / cis-ethyl esters (lb lib) with immobilized whole cell VfS-TA in presence of ketone (Illb) in batch mode The procedure was performed as presented in Example 1 modified in a way that immobilized whole cell Vibrio fluvialis transaminase (F^-TA, 50 mg) as biocatalyst and ethyl 2-(4-oxocyclohexyl)acetate (compound Illb, 2.5 mM) as the amine acceptor were used in the reaction. After 48 h reaction time, according to integration of peak areas for the ketone (Illb) and the corresponding acetamides of lb and lib, the molar fractions of the products lb, lib, and Illb were in the mixture 74.6%, 12.4% and 13.0%, respectively. Example 8 DI of trans / cis-ethyl esters (Ib+ lib) with purified soluble VfS-TA in presence of ketone (Illb) in batch mode The procedure was performed as presented in Example 1 modified in a way that ethyl 2-(4-oxocyclohexyl)acetate (compound Illb, 2.5 mM) as the amine acceptor andNi-NTA- purified Vibrio fluvialis transaminase (f' / S-TA) biocatalyst (at 0.5 mg / ml protein concentration in the final reaction mixture, supplemented with 0.2 mM piridoxal-5-phosphate (PLP)) were used in the reaction starting from 25 mM of cis / trans diastereomeric mixture (lib HCl / Ib HC1= 51:49). After 48 h reaction time, according to integration of peak areas for the ketone (Illb) and the corresponding acetamides of lb and lib, the molar fractions of the products lb, lib, and Illb were in the mixture 78.4%, 10.8% and 10.7%, respectively. Extractive workup as presented in Example 1 gave ketone (compound Illb: 1.0 mg, ~5.4 pmol, -97% yield) and crude / ra / rs-amine (compound lb with minor amount of lib): 6.2 mg, 33 pmol, 66% yield with detrans= 15.1% by GC). Recrystallization of the crude Zra«s-amine (compound lb with minor amount of lib) according to the method disclosed in WO2010 / 070368 gave trans-amine hydrochloride salt (compound IbHCl: 5.7 mg, 26 pmol, with de trans >99% by GC). Example 9 DI of trans / cis-ethyl esters (Ib+ lib) with purified soluble VfS-TA in presence of cyclohexanone in batch mode The procedure was performed as presented in Example 1 modified in a way that cyclohexanone (5 mM) as the amine acceptor and Ni-NTA-purified Vibrio fluvialis transaminase (E / S-TA) biocatalyst (at 0.5 mg / ml protein concentration in the final reaction mixture, supplemented with 0.2 mM piridoxal-5-phosphate (PLP)) were used in the reaction starting from 25 mM of cis / trans diastereomeric mixture (lib HCl / Ib HC1= 51:49). After 48 h reaction time, according to integration of peak areas for the ketone (Illb) and the corresponding acetamides of lb and lib, the molar fractions of the products lb, lib, and Illb were in the mixture 85.9%, 9.3% and 4.8%, respectively. Extractive workup as presented in Example 1 gave crude ketone (compound Illb, with minor amount of cyclohexanone: 0.4 mg) and crude / rans-amine (compound lb, with minor amount of lib): 6.1 mg, 32 pmol, 64% yield with detrans= 80.4% by GC). Dynamic isomerization of trans / cis-diastereomeric mixture of 4-substituted cyclohexane-1-amines (compounds C+T) with covalently immobilized W60C mutant of transaminase from Chromobacter violaceum in continuous flow mode Example 10 DI of trans / cis-ethyl esters (IbHCl + IlbHCl) with CvSweoc-TA covalently immobilized on porous resin in presence ofpyruvate in continuous flow mode The dynamic isomerization of the c / .s / raz / .s-diastereomeric mixture of 4-(2-ethoxy-2-oxoethyl)cyclohexan-l-aminium chloride (compounds Ib HCl + Ilb HCl) was accomplished in a laboratory scale flow reactor comprised of syringe pump (Asia® Syringe Pump system, Syrris Ltd., Royston, UK) attached to SynBioCart columns (SynBiocat, Budapest, Hungary; stainless steel outer and PTFE inner tube, inner diameter: 4 mm; total length: 70 mm; packed length: 65 mm; inner volume: 0.816 mb). The column was sealed by filter membranes made of PTFE [Whatman® Sigma-Aldrich, WHA10411311, pore size 0.45 pm]. The sealing elements were made of PTFE. PTFE tubing (1 / 16” outer diameter and 0.8 mm inner diameter, VICI AG International, Schenkon, Switzerland) and PEEK fmgertight (Sigma Aldrich) were used to connect columns (purchased from commercial vendors). Three serially connected SynBioCart columns filled with the covalently immobilized Cv5Woc-TA biocatalyst (filling weights: 375±12 mg / column) immobilized on glycerol-1,3-diglycidyl ether modified methacrylic polymer resins (ReliZyme™ EA403 / S; polymethyl methacrylate supports, particle size 1 SO-SOO pm, pore size 400-600 A) were thermostated at 40 °C with precise temperature control in an in-house made stainless steel metal block. The CvSweoc-TA biocatalyst-filled columns were prewashed by HEPES buffer (50 mM, pH=7.0) for 1 h. Then the solution of the cis / trans-diastereomeric mixture of 4-(2-ethoxy-2-oxoethyl)cyclohexan-l-aminium chloride [compounds Ib HCl + Ilb HCl, cis :trans=69.1:30.3, 20 mM, dissolved in HEPES buffer (50 mM, pH=7.0) containing DMSO as cosolvent (10% v / v ), sodium pyruvate (0.95 eq.) and PLP (l%n / n)] was pumped through the column at a flow rate of 10 pL min'1. After the stationary operation was established (~6 h), samples were taken and analyzed by GC at every hour during the stationary operation period, and the outflowing reaction products were collected for 48 h. The collected solution (25 mL) was acidified by aqueous cc. HC1 to pH 1, and the formed ketone (compound Hlb) was removed by extraction with di chloromethane (3x50 mL). After removal of the ketone, the aqueous phase was basified by addition of ammonium hydroxide (25 %) to pH 12 and the residual amine was extracted with dichloromethane (3*50 mL). The unified organic phase was extracted with saturated brine (30 mL) and dried over NazSCh and concentrated in vacuum to yield the product amine (compound lb) which was dissolved in diethyl ether and treated with HCl-gas. The precipitate was then isolated by filtration and dried to give the / rans-amine hydrochloride salt product (compound lb HC1, 11.6 mg, isolated yield 27%, detrans >99%) as a white solid. 'H NMR (500 MHz, DMSO-^) 5h: 8.09 (3H, br, N / / 3+), 4.04 (2H, q, J=7.22 Hz, OC / / 2), 2.94-2.83 (1H, m, C / L-NHf ), 2.17 (2H, d, J=7.0 Hz, C#2-COOEt), 1.93 (2H, br d, J=13.5 Hz, 2x C%qCHNH3+), 1.72 (2H, br d, J=13.0 Hz,         1.64-1.56 (1H, m, CH^- CH2COOEt), 1.32 (2H, qd, J=12.4 Hz, J=2.9 Hz, 2xC / 7ax-CHNH3+), 1.17 (3H, t, J=7.2 Hz, CHI), 1.02 (2H, qd, J=12.8 Hz, J=2.7 Hz, 2><CHax); 13C NMR (125 MHz, DMSO-A) 5c: 171.8 (CO), 59.6 (OCH2), 48.9 (CH-NHC), 40.4 (CH2-COOEt), 33.1 (CH2), 29.8 (2xCH2), 14.0 (CH3); HRMS: M+=200.16443 (delta=-0.4 ppm; C11H22O2N). HR-ESI-MS-MS (CID=35%; rel. int. %): 183(41) and 141(100). Example 11 DI of trans / cis-isopropyl esters (IdHCl + Ild HCl) with CvSw6oc-TA covalently immobilized on porous resin in presence ofpyruvate in continuous flow mode The procedure was performed as presented in Example 10 modified in a way that that four serially connected SynBioCart columns filled with the covalently immobilized CiaSWoc-TA biocatalyst were applied for the dynamic isomerization of the cisirans-diastereomenc mixture of 4-(2-isopropoxy-2-oxoethyl)cyclohexan-l-aminium chloride (compounds Id HCl + Ild HCl, 20 mM, cis:trans=51.7:48.3). The stationery operation of the reaction for 48 h afforded the Zrans-amine hydrochloride salt product (compound Id HC1,18.7 mg, isolated yield 30%, detrans>99o / o) as a white solid. 'H NMR (500 MHz, DMSO-^) 5h: 8.05 (3H, br, N / / C), 4.88 (1H, quint, J=6.3 Hz, CH-(CH3)2), 2.89-2.87 (1H, m, C / Cx-WC), 2.14 (2H, d, J=6.96 Hz, C^-COO'Pr), 1.94-1.91 (2H, m, 2*CHeq), 1.72-1.70 (2H, m, 2xCHeq), 1.63-1.55 (1H, m, C / Zax-CHzCOOTr), 1.32 (2H, qd, J=12.7 Hz, J=3.0 Hz, 2xCHax), 1.17 (6H, d, J=6.25 Hz, 2xCH3), 1.02 (2H, qd, J=12.9 Hz, J=3.1 Hz, 2xCHax 13C NMR(125 MHz, DMSO-^) 5c: 171.3 (CO), 66.9 (CH-(CH3)2), 48.9 (CH-NH3+), 40.6 (CH-CH2-COO'Pr), 33.2 (CH-CH2COO'Pr), 29.8 (CH2), 29.7 (CH2), 21.5 (CH3); HRMS M+=186.14866 (delta=-l.l ppm; CioH2o02N). HR-ESI-MS-MS (CID=35%; rel. int. %): 169(100). Example 12 DI of trans / cis-4-methylcyclohexane-l-aminium chloride (CHCl+THCl (G= H)) with CvSw6oc-TA covalently immobilized on porous resin in presence of pyruvate in continuous flow mode The procedure was performed as presented in Example 10 modified in a way that that four serially connected SynBioCart columns filled with the covalently immobilized CvSwcoc-TA biocatalyst were applied for the dynamic isomerization of the cis / trans-diastereomeric mixture of 4-methylcyclohexan-l-aminium chloride (compounds C HCl+T HCl (G= H), 20 mM, cis:trans=42:58). The stationery operation of the reaction for 24 h afforded the / rans-amine (compound T (G= H)) in dedans >99% (by GC) which was not isolated due to the volatility of the product. Example 13 DI of trans / cis-4-ethyIcyclohexane-l-aminium chloride (C HCl+T HCl (G= Me)) with CvSweoc-TA covalently immobilized on porous resin in presence of pyruvate in continuous flow mode The procedure was performed as presented in Example 10 modified in a way that that two serially connected SynBioCart columns filled with the covalently immobilized CvSWoc-TA biocatalyst were applied for the dynamic isomerization of the m / rans-diastereomeric mixture of 4-ethylcyclohexan-l-aminium chloride (compounds C HCl+T HCl (G= Me), 20 mM, cis:trans= 65.4:34.6). The stationery operation of the reaction for 24 h (6-24 h) afforded the trans-amine hydrochloride salt product (compound C HCl+T HCl (G= Me), 10.7 mg, isolated yield 30.4%, detrans>99%) as a white solid. 'H NMR (500 MHz, DMSO-^) 5h: 7.99 (3H, br, Wf), 2.91-2.86 (1H, m CHax-1.93-1.92 (2H, m, 2^CHeq), 1.75-1.74 (2H, m, 2*CHef), 1.31-1.23 (2H, qd, J=12.6 Hz, J=3.25 Hz, 2MHa,f 1.21-1.16 (2H, quint, J=15 Hz C^CHs), 1.07-1.03 (1H, m, CHax- CH2CH3), 0.94-0.88 (2H, qd, J=12.9 Hz, J=3 3 Hz, 2 / CPU), 0.86-0.83 (3H, t, J=7.5 Hz, CH2CW3); 13C NMR (125 MHz, DMSO-^) 8c: 49.42 (CH- NH3+), 37.49 (CH-CH2CH3), 30.07 (CH2), 29.92 (CH2- CHCH2CH3), 28.69 (CH2CH3), 11.27 (CH2CH3); HRMS: M+=128.14307 (delta=-2.4 ppm; CsHisN). HR-ESI-MS-MS (CID=35%; rel. int. %): 111(100) and 69(10). Example 14 DI of trans / cis-4-phenylcyclohexane-l-aminium chloride (CHCl+THCl (G= Ph)) with CvSweoc-TA covalently immobilized on porous resin in presence of pyruvate in continuous flow mode The procedure was performed as presented in Example 10 modified in a way that that two serially connected SynBioCart columns filled with the covalently immobilized CvSweoc-TA biocatalyst were applied for the dynamic isomerization of the cis / trans-diastereomeric mixture of 4-phenylcyclohexan-l-aminium chloride (compounds C HCl+T HCl (G= Ph), 15 mM, cis:trans= 26.2:73.8). The stationery operation of the reaction for 24 h (6-24 h) afforded the trara-amine hydrochloride salt product (compound C HCl+T HCl (G= Ph), (26.7 mg, isolated yield 70.7%) as a yellowish-white solid. 'H NMR (500 MHz, DMSO-^) 8h: 8.17 (3H, br, N / t%), 7.29-7.26 (2H, m, AxHmeta\ 7.247.22 (2H, m, ArHono), 7.18 (1H, tt, J7I1 Hz, J1.43 Hz, ArHpam), 3.05-3.03 (1H, m, CH^-NH3+), 2.46-2.40 (1H, m, Cffax-Ph), 2.06-2.04 (2H, m, 2*CHeq), 1.83-1.82 (2H, m, 2*CHeq); 1.57-1.44 (4H, m, 4xCJCk) 13C NMR (126 MHz, DMSO-A) 8c: 146.0 (ArC), 128.2 (ArCHmeta), 126.6 (ArCHorto), 126.0 (ArCHpara), 48.8 (CH-NH3+), 42.2 (CH-Ph), 31.4 (CH2), 30.4 (CH2); HRMS: M+=176.14312 (delta=-1.5 ppm; C12H18N). HR-ESI-MS-MS (CID=35%; rel. int. %): 159(100); 91(3) and 81(3). Example 15 DI of trans / cis-4-benzylcyclohexane-l-aminium chloride (C HCl+T HCl (G= CH2Ph)) with CvSweoc-TA covalently immobilized on porous resin in presence of pyruvate in continuous flow mode The procedure was performed as presented in Example 10 modified in a way that that only one SynBioCart columns filled with the covalently immobilized CvSw6oc-TA biocatalyst was applied for the dynamic isomerization of the cA / / ra«5-diastereomeric mixture of 4-benzylcyclohexan-l-aminium chloride (compounds C HC1+T HC1 (G= CH2Ph), 15 mM, cis:trans= 50.7:49.3). The stationery operation of the reaction for 24 h (6-24 h) afforded the trans-amine hydrochloride salt product (compound C HC1+T HC1 (G= CH2Ph), (19.8 mg, isolated yield 54.1%) as a yellowish-white solid. 'H NMR (500 MHz, DMSO-^) 5h: 8.17 (3H, br, W3+), 7.29-7.26 (2H, m, AxHmeta\ 7.247.22 (2H, m, ArHorto), 7.18 (1H, tt, J=7.11 Hz, J=1.43 Hz, AxHpara\ 3.05-3.03 (1H, m, CH^-NH3+), 2.46-2.40 (1H, m, CT / ax-Ph), 2.06-2.04 (2H, m, 2*CHeqf 1.83-1.82 (2H, m, 2*CHeqy, 1.57-1.44 (4H, m, 4 / CA%) Dynamic isomerization of czs / trans-diastereomeric mixtures of 4-substituted cyclohexane-1-amines with ATA-217 (engineered V / S-TA) in batch mode Example 16 DI of trans / cis-methyl esters (Ia+ Ila) with lyophilized A TA-217 in presence ofpyruvate in batch mode The procedure was performed as presented in Example 1 modified in a way that ATA-217 biocatalyst was used (at 1.0 mg / ml concentration) in the reaction starting from 25 mM of cis / trans diastereomeric mixture (IIa HCl / Ia HCl= 48:52) in sodium phosphate buffer (100 mM, pH 7.5) supplemented with piridoxal-5-phosphate (PLP, 0.1 mM) and sodium pyruvate as amine acceptor (0.04 eq., 1 mM) the final reaction mixture (2 ml). After 24 h reaction time, according to integration of peak areas for the ketone (Illa) and the corresponding acetamides of la and Ha, the molar fractions of the products la, Ila, and Illa in the mixture were 76.9%, 19.2% and 3.9%, respectively; representing 24.7% cis to trans conversion and detrans= 60.1% by GC. Example 17 DI of trans / cis-ethyl esters (Ib+ lib) with lyophilized ATA-217 in presence of pyruvate in batch mode The procedure was performed as presented in Example 1 modified in a way that ATA-217 biocatalyst was used (at 1.0 mg / ml concentration) in the reaction starting from 25 mM of cis / trans diastereomeric mixture (lib HCl / Ib HC1= 49:51) in sodium phosphate buffer (100 mM, pH 7.5) supplemented with piridoxal-5-phosphate (PLP, 0.1 mM) and sodium pyruvate as amine acceptor (0.04 eq., 1 mM) the final reaction mixture (2 ml). After 24 h reaction time, according to integration of peak areas for the ketone (Illb) and the corresponding acetamides of lb and Hb, the molar fractions of the products lb, lib, and Illb in the mixture were 84.6%, 11.3% and 4.0%, respectively; representing 34.0% cis to trans conversion and detrans= 76.4% by GC. Example 18 DI of cis-ethyl ester (lib) with lyophilized ATA-217 in presence ofpyruvate in batch mode The procedure was performed as presented in Example 1 modified in a way that ATA-217 biocatalyst was used (at 1.0 mg / ml concentration) in the reaction starting from 25 mM of cis diastereomer (lib HC1, deCis= 90.2%) in sodium phosphate buffer (100 mM, pH 7.5) supplemented with piridoxal-5-phosphate (PLP, 0.1 mM) and sodium pyruvate as amine acceptor (0.04 eq., 1 mM) the final reaction mixture (2 ml). After 24 h reaction time, according to integration of peak areas for the ketone (Illb) and the corresponding acetamides of lb and Hb, the molar fractions of the products lb, lib, and Illb in the mixture were 84.2%, 11.4% and 4.4%, respectively; representing 79.3% cis to trans conversion and detrans= 76.0% by GC. Example 19 DI of trans / cis-isopropyl esters (Id+ lid) with lyophilized ATA-217 in presence of pyruvate in batch mode The procedure was performed as presented in Example 1 modified in a way that ATA-217 biocatalyst was used (at 1.0 mg / ml concentration) in the reaction starting from 25 mM of cis / trans diastereomeric mixture (IId HCl / Id HCl= 69:31) in sodium phosphate buffer (100 mM, pH 7.5) supplemented with piridoxal-5-phosphate (PLP, 0.1 mM) and sodium pyruvate as amine acceptor (0.04 eq., 1 mM) the final reaction mixture (2 ml). After 24 h reaction time, according to integration of peak areas for the ketone (Hid) and the corresponding acetamides of Id and lid, the molar fractions of the products Id, lid, and Hid in the mixture were 84.4%, 10.9% and 4.7%, respectively; representing 53.4% cis to trans conversion and detrans= 'll.2% by GC. Example 20 Attempted isomerization oftrans / cis-2-(4-aminocyclohexyl)ethan-l-ol (IVa + Va) with lyophilized ATA-217 in presence ofpyruvate in batch mode The procedure was performed as presented in Example 1 modified in a way that ATA-217 biocatalyst was used (at 1.0 mg / ml concentration) in the reaction starting from 25 mM of cis / trans diastereomeric mixture (Va / TVa= 48.3:51.7) in sodium phosphate buffer (100 mM, pH 7.5) supplemented with piridoxal-5-phosphate (PLP, 0.1 mM) and sodium pyruvate as amine acceptor (0.04 eq., 1 mM) the final reaction mixture (2 ml). After 24 h reaction time, according to integration of peak areas for the ketone (Via) and the corresponding acetamides of IVa and Va, the molar fractions of the products IVa, Va, and Via in the mixture were 49.8%, 31.0% and 19.2%, respectively; representing virtually no cis to trans conversion but detrans= 23.2% by GC. Example 21 DI of trans / cis-4-(2-acetoxyethyl)cyclohexan-l-amine [compounds IV (R= Ac) + V (R= Ac)] with lyophilized ATA-217 in presence of pyruvate in batch mode The procedure was performed as presented in Example 1 modified in a way that ATA-217 biocatalyst was used (at 1.0 mg / ml concentration) in the reaction starting from 25 mM of cis / trans diastereomeric mixture of the O-acetate (V (R= Ac) HC1 / IV (R= Ac) HC1= 52.9:47.1) in sodium phosphate buffer (100 mM, pH 7.5) supplemented with piridoxal-5-phosphate (PLP, 0.1 mM) and sodium pyruvate as amine acceptor (0.04 eq., 1 mM) the final reaction mixture (2 ml). After 24 h reaction time, according to integration of peak areas for the ketone [VI (R= Ac)] and the corresponding acetamides of IV (R= Ac) and V (R= Ac), the molar fractions of the products IV (R= Ac), V (R= Ac), and VI (R= Ac) in the mixture were 59.4%, 33.2% and 7.4%, respectively; representing 12.3% cis to trans conversion and detrans= 28.3% by GC. Example 22 DI of trans / cis-4-((l,3-dioxolan-2-yl)methyl)cyclohexan-l-amine (compounds Vila + Villa) with lyophilized ATA-217 in presence of pyruvate in batch mode The procedure was performed as presented in Example 1 modified in a way that ATA-217 biocatalyst was used (at 1.0 mg / ml concentration) in the reaction starting from 25 mM of cis / trans diastereomeric mixture of the O-acetate (Vila / VIIIa= 52.0:48.0) in sodium phosphate buffer (100 mM, pH 7.5) supplemented with piridoxal-5-phosphate (PLP, 0.1 mM) and sodium pyruvate as amine acceptor (0.04 eq., 1 mM) the final reaction mixture (2 ml). After 24 h reaction time, according to integration of peak areas for the ketone (IXa) and the corresponding acetamides of Vila and Villa, the molar fractions of the products Vila, Villa, and IXa in the mixture were 74.9%, 11.7% and 13.4%, respectively; representing 22.9% cis to trans conversion and detrans= 73.0¾ by GC. Example 23 DI of trans / cis-4-((1,3-dioxan-2-yl)methyl)cyclohexan-l-amine [compounds VII (n= 2) + VUIa (n= 2)] with lyophilized ATA-217 in presence of pyruvate in batch mode The procedure was performed as presented in Example 1 modified in a way that ATA-217 biocatalyst was used (at 1.0 mg / ml concentration) in the reaction starting from 25 mM of cis / trans diastereomeric mixture of the O-acetate (VII (n= 2) / VIII (n= 2)= 51.0:49.0) in sodium phosphate buffer (100 mM, pH 7.5) supplemented with piridoxal-5-phosphate (PLP, 0.1 mM) and sodium pyruvate as amine acceptor (0.04 eq., 1 mM) the final reaction mixture (2 ml). After 24 h reaction time, according to integration of peak areas for the ketone [IXa (n= 2)] and the corresponding acetamides of VII (n= 2) and VIII (n= 2), the molar fractions of the products VII (n= 2), VIII (n= 2), and IX (n= 2) in the mixture were 60.9%, 27.3% and 11.7%, respectively; representing 9.9% cis to trans conversion and detrans= 38.0% by GC.

Claims

1. Process to produce (lr,4r)-4-substituted cyclohexane-l-amine [= tran.y-4-substituted cyclohexane-1-amine] of formula (T) starting from a diastereomeric mixture of 4-substituted cyclohexane-1-amines (formula (C) + formula (T))cis(C)or any salt of them, where in formula (T) and in formula (C) G represents a substituent, selected from- a hydrogen atom;- a Ci-6 alkyl group;- an ester moiety (-COOR), where R represents a suitable alkyl, aralkyl or aryl group, preferably a Ci-6 alkyl group, more preferably a substituent selected from methyl, ethyl, propyl and isopropyl;- a CH2-OR’ group, where R’ represents hydrogen atom, or a hydroxyl protecting group; / --0- a protected aldehyde group of formula          , where n is an integer of1 to 2;- a substituted or unsubstituted aryl group, preferably phenyl group; or- an aralkyl group, preferably benzyl groupw h e r e i n the diastereomeric mixture is reacted with a single transaminase biocatalyst in whole-cell, soluble or immobilized form in the presence of an amine acceptor used in sub-equimolar up to equimolar quantities.

2. The process according to Claim 1 characterized in that the reaction is carried out in batch mode or in continuous-flow mode.

3. The process according to Claims 1 or 2 characterized in that the starting diastereomeric mixture of the 4-substituted cyclohexane-l-amines (formula (C) + formula (T)) is in free base form.

4. The process according to Claims 1 or 2 characterized in that the starting diastereomeric mixture of 4-substituted cyclohexane-l-amines (formula (C) + formula (T)) is in salt form, preferably in hydrochloride salt form (formula (C HC1) + formula (THC1)).trans                                            cis(THCI)                         (CHCI)5. The process according to any of Claims 1 to 4 characterized in that the starting diastereomeric mixture of 4-substituted cyclohexane-l-amines (formula (C) + formula (T)) or its salt form is provided as cisltrans isomers in a ratio from about 2:98 to about 99:1.

6. The process according to any of Claims 1 to 5 characterized in that a transaminase comprising an amino acid sequence with at least about 37% sequence identity to Chromobacterium violaceum transaminase mutant (W60C) (CvSweoc-TA: SEQ ID NO.1) or to Vibrio fluvialis transaminase (V / S-TA: SEQ ID NO. 2) over a region of at least about 100 residues is used.

7. The process according to any of Claims 1 to 6 characterized in that a transaminase comprising an amino acid sequence with at least about 40% sequence identity to Chromobacterium violaceum transaminase mutant (W60C) (CvSweoc-TA: SEQ ID NO.1) or to Vibrio fluvialis transaminase (V / S-TA: SEQ ID NO. 2) over a region of at least about 100 residues is used.

8. The process according to any of Claims 1 to 7 characterized in that a transaminase comprising an amino acid sequence with at least about 50% sequence identity to Chromobacterium violaceum transaminase mutant (W60C) (Cv5w6oc-TA: SEQ ID NO.1) or to Vibrio fluvialis transaminase (V / S-TA: SEQ ID NO. 2) over a region of at least about 100 residues is used.

9. The process according to any of Claims 1 to 8 characterized in that a transaminase comprising an amino acid sequence with at least about 60% sequence identity to Chromobacterium violaceum transaminase mutant (W60C) (Cv5w6oc-TA: SEQ ID NO.1) or to Vibrio fluvialis transaminase (V / S-TA: SEQ ID NO. 2) over a region of at least about 100 residues is used.

10. The process according to any of Claims 1 to 9 characterized in that a transaminase comprising an amino acid sequence with at least about 75% sequence identity to Chromobacterium violaceum transaminase mutant (W60C) (CvSweoc-TA: SEQ ID NO.1) or to Vibrio fluvialis transaminase (V / S-TA: SEQ ID NO. 2) over a region of at least about 100 residues is used.

11. The process according to any of Claims 1 to 10 characterized in that a transaminase comprising an amino acid sequence with at least about 90% sequence identity to Chromobacterium violaceum transaminase mutant (W60C) (CvSweoc-TA: SEQ ID NO.1) or to Vibrio fluvialis transaminase (VfS-TA: SEQ ID NO. 2) over a region of at least about 100 residues is used.

12. The process according to any of Claims 1 to 11 characterized in that a suitable ketone or aldehyde is used as amine acceptor compound in sub-equimolar amounts.

13. The process according to any of Claims 1 to 12 characterized in that a 4-substituted cyclohexanone of formula K / ---\ Go=\ / --, wherein G is as described in Claim 1 for the formula (C) and formula (T), is used as amine acceptor ketone.

14. The process according to any of Claims 1 to 13 characterized in that the starting diastereomeric mixture consists of 2-(4-aminocyclohexyl)acetic acid esters of formula(I) and formula (II)trans                                             cis(I)                                                        (II)where R represents a suitable alkyl, aralkyl or aryl group, preferably a Ci-6 alkyl group, more preferably a substituent selected from methyl, ethyl, propyl and isopropyl, in free base form or in salt form.

15. The process according to Claim 14 characterized in that sodium pyruvate is used as amine acceptor ketone in sub-equimolar amounts.

16. The process according to Claim 14 characterized in that 4-substituted cyclohexanone of formula (III) is used as amine acceptor ketone / --y COOR0=\ / --'(Hi)where R represents the same suitable alkyl, aralkyl or aryl group, preferably the same Ci-6 alkyl group, more preferably the substituent selected from methyl, ethyl, propyl and isopropyl.

17. The process according to Claim 16 characterized in that ethyl 2-(4-oxocyclohexyl)acetate of formula (Illb).(iiib)is used as amine acceptor ketone.

18. The process according to Claim 16 characterized in that isopropyl 2-(4-oxocyclohexyl)acetate of formula (Hid)(Hid)is used as amine acceptor ketone.

19. The process according to any of Claims 14 to 18 characterized in that the Chromobacterium violaceum mutant (W60C) enzyme / CvSweoc-TA, characterized by SEQ ID NO. 1 / is used as transaminase in batch mode.

20. The process according to Claim 19 characterized in that the Chromobacterium violaceum mutant (W60C) transaminase / Cv5weoc-TA, characterized by SEQ ID NO. 1 / is used in whole-cell form, or in immobilized whole-cell form, or in soluble cell-free form, or in immobilized cell-free form.

21. The process according to any of Claims 14 to 18 characterized in that the Vibrio fluvialis enzyme / V / S-TA, characterized by SEQ ID NO. 2 / is used as transaminase in batch mode.

22. The process according to Claim 21 characterized in that the Vibrio fluvialis transaminase / VfS-VK, characterized by SEQ ID NO. 2 / is used in whole-cell form, or in immobilized whole-cell form, or in soluble cell-free form, or in immobilized cell-free form.

23. The process according to any of Claims 14 to 18 characterized in that a czs-selective Chromobacterium violaceum transaminase mutant (W60C) / CvSweoc-TA / is used in continuous-flow mode.

24. The process according to Claim 23 characterized in that a czs-selective Chromobacterium violaceum transaminase mutant (W60C) / CvSweoc-TA / with covalent immobilization onto a porous polymer support is used.

25. The process according to any of Claims 14 to 24 characterized in that starting from adi astereomeric mixture of 2-(4-aminocyclohexyl)acetic acid ethyl ester hydrochloride salt (formula Ib HCl + formula Ilb HCl) pure 2-( / rans-4-aminocyclohexyl)acetic ethyl ester (formula lb) is produced.trans                                             cis                                             trans(IbHCl)                               (IlbHCl)                                (lb)26. The process according to any of Claims 14 to 24 characterized in that starting from adi astereomeric mixture of 2-(4-aminocyclohexyl)acetic acid isopropyl esterhydrochloride salt (formula Id HC1 + formula lid HC1) pure 2-(trans-4-aminocyclohexyl)acetic isopropyl ester (formula Id) is produced.(Id HCl)                                 (lid HCI)                                 (Id)27. The process according to any of Claims 1 to 13 characterized in that the startingdiastereomeric mixture consists of 2-(4-aminocyclohexyl)ethan-l-ol derivatives offormula (IV) and formula (V)where R’ represents a hydrogen atom, or suitable hydroxyl-protecting group, preferablya benzyl group, in free base form or in salt form.

28. The process according to Claim 27 characterized in that sodium pyruvate is used as amine acceptor ketone in sub-equimolar amounts.

29. The process according to Claim 27 characterized in that 4-substituted cyclohexanone of formula (VI) is used as amine acceptor ketone(VI)where R’ represents the same hydrogen atom, or suitable hydroxyl-protecting group, preferably a benzyl group.

30. The process according to Claim 29 characterized in 2-(4-oxocyclohexyl)ethan-l-ol of formula (Via).(Via)is used as amine acceptor ketone.

31. The process according to any of Claims 27 to 30 characterized in that the Chromobacterium violaceum mutant (W60C) enzyme / CvSweoc-TA, characterized by SEQ ID NO. 1 / is used as transaminase in batch mode.

32. The process according to Claim 31 characterized in that the Chromobacterium violaceum mutant (W60C) transaminase / CvSweoc-TA, characterized by SEQ ID NO 1 / is used in whole-cell form, or in immobilized whole-cell form, or in soluble cell-free form, or in immobilized cell-free form.

33. The process according to any of Claims 27 to 30 characterized in that the Vibrio fluvialis enzyme IVfS-TA, characterized by SEQ ID NO. 2 / is used as transaminase in batch mode.

34. The process according to Claim 33 characterized in that the Vibrio fluvialis transaminase / V / S-TA, characterized by SEQ ID NO. 2 / is used in whole-cell form, or in immobilized whole-cell form, or in soluble cell-free form, or in immobilized cell-free form.

35. The process according to any of Claims 27 to 30 characterized in that a cis-selective Chromobacterium violaceum transaminase mutant (W60C) / CvSweoc-TA / is used in continuous-flow mode.

36. The process according to Claim 35 characterized in that a czs-selective Chromobacterium violaceum transaminase mutant (W60C) / CvSweoc-TA / with covalent immobilization onto a porous polymer support is used.

37. The process according to any of Claims 27 to 36 characterized in that starting from a di astereomeric mixture of 2-(4-aminocyclohexyl)ethan-l-ol hydrochloride salt (formula IVa HC1 + formula VaHCl) pure 2-( / rans-4-aminocyclohexyl)ethan-l-ol (formula IVa) is produced.(IVaHCI)(VaHCl)38. The process according to any of Claims 1 to 13 characterized in that the startingdiastereomeric mixture consists of 2-(4-aminocyclohexyl)acetaldehyde derivatives offormula (VII) and formula (VIII)(VII)(VIII)where n is an integer of 1 to 2.

39. The process according to Claim 38 characterized in that sodium pyruvate is used as amine acceptor ketone in sub-equimolar amounts.

40. The process according to Claim 38 characterized in that 4-substituted cyclohexanone of formula (IX) is used as amine acceptor ketone(IX)where n is an integer of 1 to 2.

41. The process according to any of Claims 38 to 40 characterized in that the Chromobacterium violaceum mutant (W60C) enzyme / CvSweoc-TA, characterized by SEQ ID NO. 1 / is used as transaminase in batch mode.

42. The process according to Claim 41 characterized in that the Chromobacterium violaceum mutant (W60C) transaminase / CvSweoc-TA, characterized by SEQ ID NO. 1 / is used in whole-cell form, or in immobilized whole-cell form, or in soluble cell-free form, or in immobilized cell-free form.

43. The process according to any of Claims 38 to 40 characterized in that the Vibrio fluvialis enzyme / V / S-TA, characterized by SEQ ID NO. 2 / is used as transaminase in batch mode.

44. The process according to Claim 43 characterized in that the Vibrio fluvialis transaminase / V / S-TA, characterized by SEQ ID NO. 2 / is used in whole-cell form, or in immobilized whole-cell form, or in soluble cell-free form, or in immobilized cell-free form.

45. The process according to any of Claims 38 to 40 characterized in that a cis-selective Chromobacterium violaceum transaminase mutant (W60C) / Cv5w6oc-TA / is used in continuous-flow mode.

46. The process according to Claim 45 characterized in that a czs-selective Chromobacterium violaceum transaminase mutant (W60C) / CvSweoc-TA / with covalent immobilization onto a porous polymer support is used.

47. The process according to any of Claims 38 to 46 characterized in that starting from a diastereomeric mixture of 4-((1,3-dioxolan-2-yl)methyl)cyclohexan-l-amines (formula Vila + formula Villa) pure / rans-4-((l,3-dioxolan-2-yl)methyl)cyclohexan-l-amine