Preperation of dicarbamates by reaction of a dialkyl- or alkylene-carbonate with a diamine

Abstract

A method of forming a compound of formula (III) according to General Scheme 1: wherein: each R1 is independently H or a C1-12 hydrocarbyl group; R4 is an organic residue; R7 in each occurrence is independently a C14 aIkyl group wherein the R7 groups may be linked to form an alkylene chain; and R10 in each occurrence is selected from C14 alkyl and C1-8 alkyl substituted with OH.

Description

[0001] Monomer

[0002] Background

[0003] There is an urgent need for a worldwide transition away from plastics derived from petroleum products.

[0004] Biobased polymers are known - i.e, polymers which are at least partially derived from renewable biomass, for example plants or microorganisms. Biopolymers are described in, for example, Farooq S. Al-Jahwari and Tasneem Pervez, "The Potential of Environmental-Friendly Biopolymers as an Alternative to Conventional Petroleum-Based Polymers", Encyclopaedia of Renewable and Sustainable Materials, Volume 5, 2020, Pages 200-206.

[0005] In 2020, polyurethanes made up nearly 8% of the world's plastics (A. Kemona and M. Piotrowska, Polymers 2020, 12(8)). Bio-based polyurethanes are disclosed in, for example, N Karak et al, "Biopolymers and Biotech Admixtures for Eco-Efficient Construction Materials", 2016, Pages 333- 368.

[0006] Joshi et al "Development of L-Lysine Based Biodegradable Polyurethanes and Their Dual-Responsive Amphiphilic Nanocarriers for Drug Delivery to Cancer Cells", ACS Appl. Polym. Mater. 2019, 1, 7, 1866-1880 discloses L-lysine based polyurethanes made by a solvent and isocyanate free melt transurethane polycondensation approach. However, lysine dicarbamate disclosed in this reference is formed using methyl chloroformate, which is a petroleum-based product and which is formed from the highly toxic substance phosgene.

[0007] Oliver Kreye et al, "Sustainable routes to polyurethane precursors", Green Chem. 2013, 15, 1431 discloses isocyanate and phosgene-free polyurethane monomer synthesis.

[0008] Peter Olsen et al, "Cyclic allylic carbonates as a renewable platform for protecting chemistry in water", Green Chem., 2018, 20, 3186 discloses allylic carbonates as allylcarbamate precursors.

[0009] Therefore, there is a need for monomers suitable for forming polyurethanes from a renewable resource. Summary of the Invention

[0010] The present inventors have found that dicarbamates may be formed by reaction of a dialkyl- or alkylene-carbonate with a diamine. Each of these starting materials may be from renewable, biobased sources which enables sustainable dicarbamate formation.

[0011] Accordingly, in a first aspect the invention provides a method of forming a compound of formula (III) according to General Scheme 1:

[0012] General Scheme 1 wherein: each R1is independently H or a C1-12 hydrocarbyl group;

[0013] R4is an organic residue;

[0014] R7in each occurrence is independently a C1-4 a Ikyl group wherein the R7groups may be linked to form an alkylene chain; and

[0015] R10in each occurrence is selected from C1-4 alkyl and C1-8 alkyl substituted with OH.

[0016] Preferably, at least one of the compounds of formulae (I) and (II) is a bio-based compound, more preferably a 100% bio-based compound. Preferably, both compounds of formulae (I) and (II) are bio-based compounds.

[0017] R4of the starting material may be the same as or different from R4of the product. For example, if the starting material comprises a group COOH then the product may comprise the same group COOH or a salt thereof. Surprisingly, despite amino acids' classical insolubility in organic solvents, the inventors have identified an improved method to synthesise compounds according to General Scheme 1-b which can be applied to amino acids.

[0018] Accordingly, in another aspect, the invention provides a method of forming a compound of formula (lll-b) according to General Scheme 1-b:

[0019] General Scheme 1-b wherein: each R1is independently H or a C1.12 hydrocarbyl group;

[0020] R14is an organic residue;

[0021] R7in each occurrence is independently an optionally substituted C14 a Ikyl group wherein the R7groups may be linked to form an alkylene chain;

[0022] R10in each occurrence is selected from C1.4 alkyl and Ci-8 alkyl substituted with OH; and Q is selected from OH, O‘M+, OR3and NR52 wherein R3is a substituent; R5independently in each occurrence is H or a substituent; and M+is a metal or organic cation.

[0023] In some embodiments, R1is H.

[0024] In some embodiments, R7is methyl.

[0025] In some embodiments, R7groups are linked to form ethylene. R14is preferably an optionally substituted Ci-ealkylene, more preferably an optionally substituted methylene.

[0026] In some embodiments, the compound of formula (1-b) is a compound of formula (l-c): In some embodiments, R13is the side chain of any one of the proteogenic, natural or essential amino acids, including: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, selenocysteine, and pyrrolysine.

[0027] In some embodiments, R13is the side chain of any one of the natural amino acids, including: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine.

[0028] In some embodiments, R1is H.

[0029] In some embodiments, R4is selected from linear, branched or cyclic C1.40 alkylene which is optionally substituted with a group of formula -C(=O)X or -C(=O)Y wherein X is selected from OH and O‘M+and Y is selected from OR3and NR52 wherein R3is a substituent; R5independently in each occurrence is H or a substituent; and M+is a metal or organic cation; and in which a C atom of the Ci.4oalkylene which is not bound directly to NHR1may be replaced with 0, S or S-S.

[0030] In some embodiments, the compound of formula (l-b) is an at least partially bio-based compound.

[0031] In some embodiments, the compound of formula (l-b) is a 100% bio-based compound.

[0032] In some embodiments, the compound of formula (II) is selected from dimethylcarbonate and ethylene carbonate.

[0033] In some embodiments, the compound of formula (II) is an at least partially bio-based compound.

[0034] In some embodiments, the compound of formula (II) is a 100% bio-based compound.

[0035] The reaction may be conducted without a solvent, in particular where the compound of formula (II) is selected from dimethylcarbonate and ethylene carbonate. In these embodiments, dimethylcarbonate and ethylene carbonate may effectively be the solvent for the reaction.

[0036] Where present, the reaction solvent of the method of General Scheme (I) or General Scheme (l-b) preferably comprises or consists of water, Ci-e alcohols or a mixture thereof. The reaction solvent preferably comprises or consists of ethanol.

[0037] The reaction is suitably conducted in the presence of a base, optionally an ammonium hydroxide or metal hydroxide, for example an alkali or alkali earth hydroxide. The present inventors have found that reactions as described herein can proceed readily to completion without any significant formation of side-products. Accordingly, purification of the product of the method of General Scheme (I) or General Scheme (l-b) optionally consists of filtration and solvent removal.

[0038] Detailed Description of the Invention

[0039] Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise," "comprising," and the like are to be construed in an inclusive sense, as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to." Additionally, the words "herein," "above," "below," and words of similar import, when used in this application, refer to this application as a whole and not to any particular portions of this application. Where the context permits, words in the Detailed Description using the singular or plural number may also include the plural or singular number respectively. The word "or," in reference to a list of two or more items, covers all of the following interpretations of the word: any of the items in the list, all of the items in the list, and any combination of the items in the list. References to a chemical element include isotopes of that element.

[0040] The elements and acts of the various examples described below can be combined to provide further implementations of the technology. Some alternative implementations of the technology may include not only additional elements to those implementations noted below, but also may include fewer elements.

[0041] These and other changes can be made to the technology in light of the following detailed description. While the description describes certain examples of the technology, and describes the best mode contemplated, no matter how detailed the description appears, the technology can be practiced in many ways. As noted above, particular terminology used when describing certain features or aspects of the technology should not be taken to imply that the terminology is being redefined herein to be restricted to any specific characteristics, features, or aspects of the technology with which that terminology is associated. In general, the terms used in the following claims should not be construed to limit the technology to the specific examples disclosed in the specification, unless the Detailed Description section explicitly defines such terms. Accordingly, the actual scope of the technology encompasses not only the disclosed examples, but also all equivalent ways of practicing or implementing the technology under the claims. To reduce the number of claims, certain aspects of the technology are presented below in certain claim forms, but the applicant contemplates the various aspects of the technology in any number of claim forms.

[0042] In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of implementations of the disclosed technology. It will be apparent, however, to one skilled in the art that embodiments of the disclosed technology may be practiced without some of these specific details.

[0043] "Lysine" as used herein includes any lysine enantiomer or lysine racemic mixture. L-lysine is preferred.

[0044] "Lysine-based" compounds as used herein means lysine and derivatives of the carboxylic acid group of lysine including carboxylates with a metal or organic cation; carboxylic acid esters; and amides.

[0045] A "bio-based" substance as described herein means a substance that is derived at least partially from renewable biomass, for example plants or microorganisms.

[0046] Bio-based content of compounds as described herein is determined by either Method B or Method C of the ASTM D6866-12 test as set out in https: / / www.astm.org / d6866-12.html, version dated 24 June 2016.

[0047] Compounds of formula (I)

[0048] Compounds of formula (I) have formula:

[0049] Each R1is independently H or a C1.12 hydrocarbyl group. Exemplary C1.12 hydrocarbyl groups are C1.12 alkyl and phenyl which may be unsubstituted or substituted with one or more Ci-e alkyl groups.

[0050] Preferably, each R1is H.

[0051] R4is an organic residue.

[0052] Optionally, each R4is selected from linear, branched or cyclic C1.40 alkylene which is optionally substituted with a group of formula -C(=0)X or -C(=O)Y wherein X is selected from OH and O‘M+and Y is selected from OR3and NR52 wherein R3is a substituent; R5independently in each occurrence is H or a substituent; and M+is a metal or organic cation; and in which a C atom of the Ci-4o alkylene which is not bound directly to NHR1may be replaced with 0, S or S-S.

[0053] M+may be a metal cation or a non-metallic cation. Exemplary metal cations M+are alkali metal cations, preferably Li+, Na+or K+. Exemplary non-metallic cations include ( N R1:L4)+wherein R11in each occurrence is independently H or a substituent, preferably H or C1.12 hydrocarbyl.

[0054] Optionally, R3is C1.20 alkyl; aryl (e.g. phenyl or naphthyl); heteroaryl (e.g. furan) or C1.20 alkyl substituted with aryl or heteroaryl. Optionally, R5is H; C1.20 alkyl; aryl (e.g. phenyl or naphthyl); heteroaryl (e.g. furan) or C1.20 alkyl substituted with aryl or heteroaryl.

[0055] A wide range of bio-based diamines of formula (I) are available to the skilled person. Examples include lysine and derivatives thereof in which COOH of lysine is converted to a -C00‘M+, ester or amide group; priamine; cadaverine; and cystamine.

[0056] Compounds of Formula (l-b)

[0057] The compound of formula (l-b) has formula:

[0058] Q p14

[0059] Y NHR1

[0060] (l-b)

[0061] R1may be as described with reference to Formula (I).

[0062] Q. is selected from OH, OTvT, OR3and NR52 wherein R3is a substituent; R5independently in each occurrence is H or a substituent; and M+is a metal or organic cation. R3, R5and M+are as described with reference to Formula (I).

[0063] The compound of formula (l-b) is suitably an amino acid or a derivative thereof, preferably a salt, ester or amide thereof. The amino acid may be a proteogenic amino acid. The amino acid may be a natural amino acid. The amino acid may be an essential amino acid.

[0064] Compounds of formula (II)

[0065] Compounds of formula (II) have formula:

[0066] R7in each occurrence is independently a C1-4 alkyl group wherein the R7groups may be linked to form an alkylene chain R8, preferably a C2-4alkylene chain.

[0067] In the case where R7groups are not linked, reaction of the compound of formula (II) with an amine group of the diamine of formula (I) forms a group of formula:

[0068] In the case wherein R7groups are linked to form a group R8, reaction of the compound of formula (II) with an amine group of the diamine of formula (I) forms a group of formula:

[0069] Bio-based compounds of formula (II) available to the skilled person include dimethylcarbonate and ethylene carbonate.

[0070] Reaction conditions

[0071] The reaction between the compounds of formulae (I) and (II) may be performed in the absence of a solvent, or in water in the case of a water-soluble compound of formula (II) such as lysine.

[0072] The reaction may or may not be carried out in the presence of a base. Any suitable base may be used, for example an inorganic base such as a metal hydroxide or metal carbonate or an organic base, for example triazabicyclodecene.

[0073] The reaction may take place at a temperature in the range of about 0-100 °C.

[0074] Applications

[0075] A dicarbamate compound of formula (III) may be used as a monomer with a diol monomer of formula (IV) to form a polyurethane having a repeating structure of formula (V) as shown in General Scheme 2: wherein R2is an organic residue, and is optionally selected from: linear, branched or cyclic C1-12 alkylene, preferably linear, branched or cyclic C2-6 alkylene; a group of formula -R13-[OR13]n- wherein R13is a C2-6 alkylene, preferably ethylene, propylene or butylene, and n is 1-200, optionally 1-100; a group of formula -R^A -R6- wherein R6in each occurrence is independently a C1-4 alkylene group and Ar1is an aromatic or heteroaromatic group, preferably furan; and a non-aromatic heterocyclic group substituted with two hydroxyl groups; a polyester group, optionally a group of formula -[Z-R8-Z-R9]n- wherein R8and R9are each independently selected from Ci-ealkylene and phenylene; Z is -O-C(=O)- or -C(=O)O-; and n is 1-100, optionally 1-100.

[0076] A wide range of bio-based diols are available to the skilled person, for example propylene glycol, polyethylene glycol, polyester, polytetrahydrofuran, isosorbide, 2,5-bis(hydroxymethyl)furan, 1,3- propanediol, 1,4-butanediol and 1,5-pentanediol. By use of bio-based compounds of formula (III) and (IV), a wide range of sustainable, bio-based polyurethanes may be formed.

[0077] The present inventors have found that compounds of formula (III -b) may undergo polymerisation to form a repeat unit of formula:

[0078] The polymer may be a homopolymer.

[0079] The polymer may be a copolymer, for example a copolymer formed by polymerisation of a compound of formula (lll-b) and a diol, for example a diol of formula (IV). Examples 2

[0080] Dimethylcarbonate Lysine dicarbamate

[0081] L-Lysine (1.00 g, 6.84 mmol) and H2O (250 pL) were added to a flask and stirred. In a separate vessel, KOH (0.478 g, 8.55 mmol) was added to stirring H2O (250 pL) to dissolve. With the Lysine solution in an ice bath, the KOH solution was added dropwise, then dimethylcarbonate (10.4 mL, 123 mmol) was added, and the mixture was removed from ice and stirred for 20 minutes until all solids had been dissolved. A stopper and needle were then placed on the flask before stirring on heat at 90 °C for 16 hours.

[0082] Once complete the solvents were removed in vacuo yielding a yellow oil, which was dissolved in H2O (5 mL). With the mixture in an ice bath, concentrated HCI (1 mL) was added dropwise until the pH was 1, and the mixture was then extracted (EtOAc 3 x 5 mL), dried over MgSO4 and the solvent was removed in vacuo up to 90 °C yielding the desired product as a pale-yellow oil (0.684 g, 38%).

[0083] XH NMR (400 MHz, DMSO) 6 12.37 (br s, 1H), 7.40 (d, J = 7.9 Hz, 1H), 7.09 (t, J = 5.9 Hz, 1H), 3.92 - 3.81 (m, 1H), 3.53 (s, 3H), 3.50 (s, 3H), 2.94 (dt, 2H), 1.71 - 1.48 (m, 2H), 1.44 - 1.20 (m, 4H).

[0084] 13C NMR (101 MHz, DMSO) 6 174.2, 156.9, 156.8, 53.9, 51.5, 51.3, 40.1, 30.6, 29.1, 23.0.

[0085] FTIR: Vmax / cm'13332 (N-H), 2942 (C-H), 1684 (C=O), 1524 (N-H), 1459 (C-OH), 1246 (C-N), 771 (C-H).

[0086] Priamine:

[0087] Priamine Dimethylcarbonate

[0088] Priamine 1075 (3.0 g) was added to a 50 mL round bottom flask followed by triazabicyclodecene (0.07g) and dimethyl carbonate (4.5 mL) the solution was heated to 80 °C and stirred for 5 hours. The reaction mixture was allowed to cool to room temperature then Et20 (20 mL) was added, and the organic layer was washed with water (3 x 10 mL) and dried over MgSO4and concentrated to yield a yellow oil (3.16 g, 86% yield).

[0089] XH NMR (400 MHz, CDCI3) 64.75 (br s, 2H), 3.64 (s, 6H), 3.14 (q, J = 6.8 Hz, 4H), 1.62 - 0.69 (m, 86H).13C NMR (101 MHz, CDCI3) 6 157.17, 54.92, 52.02, 41.19, 41.05, 37.47, 37.20, 33.76, 32.84, 32.03,

[0090] 30.24, 30.11, 29.93, 29.81, 29.76, 29.70, 29.66, 29.47, 29.40, 27.19, 26.84, 22.79, 19.81, 14.29, 14.22.

[0091] FTIR: Vmax / cm'1: 3330 (N-H), 2920 (C-H), 2851 (C-H), 1701 (C=O), 1528 (N-H), 1457 (C-H), 1250 (C-N), 750 (C-H).

[0092] Cadaverine:

[0093] 24 h

[0094] Cadaverine Dimethylcarbonate

[0095] Same procedure as Priamine

[0096] Bis(2-hydroxyethyl) (disulfanediylbis(ethane-2,l-diyl))dicarbamate:

[0097] Cystamine Ethylene Carbonate

[0098] Cystamine (1.02 g, 6.71 mmol) and ethylene carbonate (2.07 g, 23.5 mmol) were added to a 50 mL round bottom flask which was subsequently purged, placed under N2atmosphere, and heated at 80 °C. This mixture was left to stir for 24 hours to form a brown solution, which then yielded the desired product as a brown solid upon cooling to room temperature.

[0099] XH NMR (400 MHz, DMSO) 6 7.29 (t, J = 5.7 Hz, 2H), 4.73 (t, J = 5.3 Hz, 2H), 3.95 (t, J = 5.2 Hz, 4H), 3.53 (q, J = 5.3 Hz, 4H), 3.25 (q, J = 6.2 Hz, 2H), 2.76 (t, J = 6.9 Hz, 4H).13C NMR (101 MHz, DMSO) 6 156.4, 65.0, 59.4, 39.7, 37.5.

[0100] FTIR: Vmax / cm'13319 (N-H), 2950 (C-H), 1802 (C=O), 1774 (C=O), 1684 (C-O), 1533 (N-H), 1258 (C-N), 1148 (C-O-C). l,5-Bis-(2-hydroxy-ethoxycarbonylamino)-pentane:

[0101] Cadaverine (2.11 mL, 18.0 mmol, 1.0 eq) and ethylene carbonate (5.54 g, 62.9 mmol, 3.5 eq) were added to a round bottom flask which was subsequently purged, placed under N2 atmosphere, and heated to 80 °C. This mixture was left to stir for 3 hours to a yellow-orange oil. Unreacted material was then removed in vacuo yielding the desired product as a cream solid upon cooling to room temperature (4.54 g, 91%).

[0102] Compounds may be synthesised according to the below general formula: wherein R is H, a cation M+or C1.12 hydrocarbyl. R of the product may be the same as or different from R of the starting material. Optionally, -OR is OH in the starting material and O‘M+in the product.

[0103] Lysine bis( hydroxyethylen ecarbam ate)

[0104] To lysine (3.38 g, 23.2 mmol) suspended in ethanol (40 ml) was added KOH (1.30 g, 23.2 mmol). The mixture was heated at 50 °C with stirring until all solids had dissolved. Ethylene carbonate (4.08 g, 46.3 mmol) was added to the solution, and heated at reflux for five hours. After this time the reaction mixture was cooled to 0 -C, and trimethylsilyl chloride (2.94 ml, 23.3 mmol) was added slowly. After addition, the reaction mixture was held at 0 -C for one hour before filtering. Volatiles were removed from the filtrate under reduced pressure to give lysine b / s(hydroxyethylenecarbamate) in 95% yield.

[0105] Lysine ethyl ester bis(hydroxyethylenecarbamate)

[0106] To lysine (3.38 g, 23.2 mmol) suspended in ethanol (40 ml) was added KOH (1.30 g, 23.2 mmol). The mixture was heated at reflux with stirring until all solids had dissolved. Ethylene carbonate (4.08 g, 46.3 mmol) was added to the solution, and heating at reflux was continued for five hours. After this time the reaction mixture was cooled to 0 -C, and trimethylsilyl chloride (8.8 ml, 97 mmol) was added slowly. After addition, the reaction mixture was heated at reflux for 16 hours. Ethanol was removed under reduced pressure. The remaining oil was taken up in saturated NaHCOa, and this solution was extracted three times with chloroform. The chloroform fractions were combined, dried using MgSC>4 and solvent removed under reduced pressure to give lysine ethyl ester b / s(hydroxyethylenecarbamate).

[0107] Potassium lysinate bis(hydroxyethylenecarbamate)

[0108]

[0109] To lysine (9.87 g, 67.5 mmol) suspended in ethanol (60 ml) was added KOH (3.79 g, 67.5 mmol). The mixture was heated to 40 -C with stirring until all solids had dissolved. Ethylene carbonate (11.90 g, 135.1 mmol) was added to the solution, which was then heated at reflux for five hours. After cooling to room temperature, all volatiles were removed under reduced pressure to give potassium lysinate b / s(hydroxyethylenecarbamate) (24.3 g, 100%) as a highly viscous, colourless oil, which may crystallise if left for an extended time.

[0110] Ethyl N2,N6-bis(methoxycarbonyl)lysinate using TMSCI

[0111] To a solution of the Lysine dicarbamate (0.5 g, 1.91 mmol) in dry ethanol (11.2 mL) was added trimethylsilyl chloride (0.73 mL, 5.73 mmol) at 0 °C. The reaction mixture was then stirred for 18 hours at room temperature and then concentrated and placed under high vacuum to afford the intermediate ethyl ester as a colourless oil in quantitative yield.

[0112] XH NMR (400 MHz, CDCI3): 6 5.30 (br s, 1H), 4.31 (br s, 1H), 4.23 - 4.14 (m, 1H), 3.78 - 3.69 (m, 2H), 3.68 (s, 3H), 3.66 (s, 3H), 3.15 (t, 2H), 1.89 - 1.76 (m, 1H), 1.72 - 1.59 (m, 1H), 1.58 - 1.29 (m, 4H), 1.29 - 1.20 (m, 3H).

[0113] 13C NMR (101 MHz, CDCI3): 6 172.7, 157.4, 156.8, 61.6, 53.7, 52.4, 52.2, 40.7, 32.3, 29.5, 22.3, 14.3.

[0114] FTIR: Vmax / cm'13327 (N-H), 2948 (C-H), 1694 (C=O), 1523 (N-H), 1448 (C-H), 1248 (C-N), 1187 (C-O-C), 779 (C-H).

Claims

Claims1. A method of forming a compound of formula (III) according to General Scheme 1:General Scheme 1 wherein: each R1is independently H or a C1-12 hydrocarbyl group;R4is an organic residue;R7in each occurrence is independently a C1-4 alkyl group wherein the R7groups may be linked to form an alkylene chain; andR10in each occurrence is selected from C1-4 alkyl and C1-8 alkyl substituted with OH.

2. The method according to claim 1 wherein each R1is H.

3. The method according to claim 1 or 2 wherein R4is selected from linear, branched or cyclic Ci-4o alkylene which is optionally substituted with a group of formula -C(=O)X or -C(=O)Y wherein X is selected from OH and O‘M+and Y is selected from OR3and NR52 wherein R3is a substituent; R5independently in each occurrence is H or a substituent; and M+is a metal or organic cation; and in which a C atom of the Ci.4oalkylene which is not bound directly to NHR1may be replaced with 0, S or S-S.

4. The method according to any one of the preceding claims wherein the compound of formula (I) is selected from lysine and derivatives thereof in which COOH of lysine is converted to a - COOTvT, ester or amide group; priamine; cadaverine; and cystamine.

5. The method according to any one of the preceding claims wherein the compound of formula (I) is an at least partially bio-based compound.

6. The method according to claim 5 wherein the compound of formula (I) is a 100% bio-based compound.

7. The method according to any one of the preceding claims wherein the compound of formula (II) is selected from dimethylcarbonate and ethylene carbonate.

8. The method according to any one of the preceding claims wherein the compound of formula (II) is an at least partially bio-based compound.

9. The method according to claim 8 wherein the compound of formula (II) is a 100% bio-based compound.

10. The method according to any one of the preceding claims wherein the reaction of General Scheme (I) is performed in a solvent comprising water, an alcohol or a mixture thereof.

11. The method according to any one of claims 1-9 wherein the reaction of General Scheme (I) is performed without a solvent.

12. The method according to any one of the preceding claims wherein the reaction of General Scheme (I) is performed in the presence of a hydroxide.

13. A method of forming a compound of formula (lll-b) according to General Scheme l-b:General Scheme l-b wherein: each R1is independently H or a C1.12 hydrocarbyl group;R14is an organic residue;R7in each occurrence is independently a C1.4 alkyl group wherein the R7groups may be linked to form an alkylene chain;R10in each occurrence is selected from C1.4 alkyl and Ci-8 alkyl substituted with OH; and Q is selected from OH, OTvT, OR3and NR52 wherein R3is a substituent; R5independently in each occurrence is H or a substituent; and M+is a metal or organic cation .

14. A method according to claim 13 wherein the compound of formula (l-b) is a compound of formula (l-c):wherein R13is a side chain of any one of the 20 essential amino acids.

15. The method according to claim 13 or 14 wherein the reaction of General Scheme (l-b) is performed in a solvent comprising an alcohol.

16. The method according to claim 13 or 14 wherein the reaction of General Scheme (l-b) is performed without a solvent.

17. The method according to any one of claims 13-16 wherein the reaction of General Scheme (l-b) is performed in the presence of a hydroxide.

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