Preparation method of pentethyl quinamidine optical isomer
A technology for optical isomers and penhyclidine is applied in the field of stereoselective synthesis of penhyclidine optical isomers, which can solve the problems of time-consuming and labor-intensive and unfavorable for large-scale synthesis
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Embodiment 1
[0020] Embodiment 1, the preparation of (2S, 5S)-2-tert-butyl-5-phenyl-1,3-dioxan-4-one (IIa)
[0021] Add 20 g (0.13 mol) of S-mandelic acid into 200 mL of n-pentane, add 21.2 mL of pivalaldehyde (content 80%, 0.16 mol, purchased from Fluka Company), then add 0.5 mL of trifluoromethanesulfonic acid, and reflux for 6 hours , Remove the generated water with a water separator. Cool to room temperature, add 100mL 8% sodium bicarbonate solution, distill off n-pentane under reduced pressure, filter to obtain (2S,5S)-2-tert-butyl-5-phenyl-1,3-dioxane-4 - Ketone (IIa), yield 27.1g, melting point 100-102°C, yield 95%, elemental analysis, theoretical value %: C 70.89, H 7.32; experimental value %: C 70.81, H 7.39. 1 H-NMR: δ (ppm, CDCl 3 ), 1.10 (s, 9H), 5.25 (s, 1H), 5.38 (s, 1H), 7.47 (m, 5H).
Embodiment 2
[0022] Embodiment 2, the preparation of (2R, 5R)-2-tert-butyl-5-phenyl-1,3-dioxan-4-one (IIb)
[0023] With reference to the method of Example 1, using (R)-mandelic acid as raw material, synthesize (2R, 5R)-2-tert-butyl-5-phenyl-1,3-dioxan-4-one (IIb), Melting point 100-102°C, yield 97%, elemental analysis, theoretical value %: C 70.89, H 7.32; experimental value %: C 70.83 H 7.30. 1 H-NMR: δ (ppm, CDCl 3 ), 1.12 (s, 9H), 5.23 (s, 1H), 5.36 (s, 1H), 7.49 (m, 5H).
Embodiment 3
[0024] Example 3, Preparation of (2S, 5R)-2-tert-butyl-5-phenyl-5-(cyclopentyl-1-hydroxyl)-1,3-dioxan-4-one (IIIa)
[0025] Dissolve 10 g (45 mmol) of (2S, 5S)-2-tert-butyl-5-phenyl-1,3-dioxan-4-one in 70 mL of dry tetrahydrofuran, cool to -78°C, add 60 mL of di( Lithium trimethylsilyl)amide (solution in tetrahydrofuran, 1.0M). 65mmol of cyclopentanone was added dropwise under stirring, the reaction was stirred for 2 hours, and 15mL of saturated sodium hydrogen phosphate solution and 200mL of saturated ammonium chloride solution were added dropwise. The organic layer was separated, the aqueous layer was extracted with ethyl acetate, the organic layers were combined, dried, and the solvent was evaporated to obtain (2S, 5R)-2-tert-butyl-5-phenyl-5-(cyclopentyl-1- Hydroxy)-1,3-dioxan-4-one (IIIa), yield 10.5 g, yield 74%. 1 H-NMR: δ (ppm, CDCl 3 ), 0.88 (s, 9H), 1.52-2.06 (m, 8H), 5.52 (s, 1H), 7.31 (m, 3H), 7.78 (dd, J=1.5, 8.3Hz, 2H).
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