SK277921B6 - Method of preparation of n-succinimidylcarbonates - Google Patents

Abstract

N-Succinimidylcarbonates with general formula I, where Ar means 9-fluoroenyl, phenyl, or substituted by substituents from group of halogen atom, nitrogroup, alkyl with 1 to 4 atoms of carbon or trifluoromethyl, or heteroaromatic surplus with 5 or 6 atoms in ring and with one or two atoms of nitrogen or sulfate, is prepared by reaction of alcohol ArCH sub.2OH, where Ar has mentioned meaning with phosgene by presence on inert solvent, which can be mixed with water by formation of corresponding chloroformite ester acid and reactive mixture is without isolation of intermediate introduced in to reaction with water solution of N-hydroxysuccinimide by presence of hydrogencarbonate or carbonate ammonium, alkaline metal or metal of alkaline soils as neutralizing agent and compound with general formula I is isolated from organic phase.

Description

The invention relates to a process for the preparation of N-succinimidyl carbonates by reacting phosgene with an alcohol to the corresponding chloroformic acid esters and subsequent reaction with N-hydroxysuccinimide.

BACKGROUND OF THE INVENTION

N-Succinimidyl carbonates are used in the synthesis of peptides to introduce suitable amino protecting groups for amino acids. N-succinimidyl carbonates are preferred due to their selective reaction with the corresponding acid chlorides. A particularly suitable protecting group is a 9-fluorenylmethyloxycarbonyl group, since this group is readily cleavable in a mildly alkaline environment.

In principle, two reaction processes are known for the preparation of N-succinimidyl carbonates.

Ten Kortenaar et al., Int. Peptide Protein Research 27 (1986), p. 398, describes the preparation of 9-fluorenylmethylsuccinimidyl carbonates by phosgenation of 9-fluorenylmethanol followed by reaction with N-hydroxysuccinimide. Phosgenation is accomplished by adding alcohol to liquid phosgene at -78 ° C. The resulting chloroformate is isolated, dissolved in dioxane and reacted with N-hydroxysuccinimide in the presence of triethylamine as a neutralizing agent at a temperature of 10 to 1 ° C.

According to L. A. Carpino, G. Y-Han, J. Org. Chem., Vol. 37, (1972), p. 3404 ff can also be carried out by adding alcohol to a solution of phosgene in dichloromethane.

In both processes, the concentration of phosgene in the solution is very high, which is unacceptable in terms of safety. Excess phosgene must be removed after phosgenation is complete. In the following reaction, hydrogen chloride, which is produced as a by-product of phosgenation, also binds to the amine used as neutralizing agent, in addition to the chloroformic ester, to form the amine hydrochloride. This substance must also be removed. In addition, the resulting amine hydrochlorides are by-products which are harmful to the environment and must be carefully removed. Moreover, due to the volatility of the fluorenylmethyl ester, the reaction of the chloroformic acid ester with N-hydroxysuccinimide in the presence of an organic amine can produce dibenzofulvine relatively easily as a cleavage product, thereby reducing the yield.

According to A. Paquet, Can. J. Chem. 60 (1982), 976ff, 9-fluorenylmethylsuccinimidyl carbonate can also be obtained by phosgenation of the N-hydroxysuccinimide salt with cyclohexylamine followed by reaction of the succinimidyl chloroformate ester with 9-fluorenylmethanol. To this end, liquid phosgene is fed to the N-hydroxysuccinimide salt suspension at -30 ° C, the resulting cyclohexylamine hydrochloride is separated and the succinylimidyl chloroformate ester is isolated. The following reaction with 9-fluorenylmethanol is carried out in dichloromethane in the presence of pyridine as neutralizing agent.

Also in this process, it is necessary to remove the by-products of the phosgenation and also the excess phosgene before the reaction with the chloroformic acid ester. In addition, in the phosgenation process and in the further reaction of the chloroformic acid ester, an amine hydrochloride is also formed which must also be removed.

It is clear that known processes for the production on an industrial scale are not suitable for the preparation of N-hydroxysuccinimidyl carbonates.

It would therefore be desirable to design a process in which it would not be necessary to isolate the intermediate product and, conversely, to easily separate the formed inorganic salts.

SUMMARY OF THE INVENTION

The present invention relates to a process for the preparation of the N-succinimidyl carbonates of the formula I

wherein Ar is 9-fluorenyl, phenyl optionally substituted with halogen, nitro or C 1 -C 4 alkyl, or a heteroaromatic radical of 5 or 6 ring atoms and one or two nitrogen or sulfur atoms, the method of manufacture comprising: reacts an alcohol of formula Π

Ar = CH 3 OH (Π) wherein Ar is as defined above; with phosgene in the presence of an inert, water-miscible solvent to form the chloroformic acid ester of the general formula ΙΠ

N - CH ₂ - O - C - Cl (III)

II o

wherein Ar is as defined above; and reacting the reaction mixture without isolating the compound of formula H1 with an aqueous solution of N-hydroxysuccinimide in the presence of an alkali or alkaline earth metal bicarbonate or carbonate or ammonium bicarbonate or carbonate as a neutralizing agent, then the compound of formula I thus obtained from the organic phase recovered.

The starting materials used are alcohols of the formula I in which Ar represents a fluorenyl radical or a phenyl radical optionally substituted by one or more substituents from the group halogen, for example chlorine, bromine or fluorine, nitro, C1-C4-alkyl or trifluoromethyl . Examples of substituted phenyl radicals include 2-chlorophenyl, 4-chlorophenyl, 2,4-dichlorophenyl, 2-bromophenyl, 4-fluorophenyl, methylienyl, trifluoromethylphenyl. Further, Ar may be a heteroaromatic ring having 5 or 6 ring atoms and one or two nitrogen or sulfur atoms as heteroatoms, for example pyridyl, pyridazinyl, pyrimidyl or thienyl.

Preference is given to using alcohols of the formula

Π in which Ar is 9-fluorenyl, phenyl or 2-chlorophenyl.

The reaction of the alcohol with phosgene is carried out in a solvent which is miscible with water and inert under the reaction conditions, for example a cyclic ether such as tetrahydrofuran or dioxane or a non-alkaline ether such as a di-, tri- or tetraethylene glycol diethyl ether. The reactants are usually used in equivalent amounts. Phosgene may be utilized in excess of about 10% by weight to complete the reaction.

In carrying out the reaction, it is desirable to introduce phosgene into a mixture of alcohol and solvent, since in this way it is possible to maintain a low concentration of phosgene in solution. The temperature of the phosgenation is kept between 0 and 20'C.

The post-phosgenation reaction solution is added to an aqueous solution of N-hydroxysuccinimide, optionally in admixture with an inert solvent and containing ammonium bicarbonate or carbonate, an alkali metal or an alkaline earth metal.

Usually, 1 mole of N-hydroxysuccinimide is used per mole of alcohol. The reaction produces 2 moles of hydrochloric acid per mole of phosgene. Thus, two equivalents of neutralizing agent are required for neutralization. Examples of a suitable neutralizing agent are potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate, ammonium bicarbonate or ammonium carbonate.

Chloroformate esters are more or less sensitive to hydrolysis depending on the stability of the alcohol component. However, in the aqueous solution, the chloroformic esters used in the process of the invention do not undergo any hydrolysis of the chloroformic esters with subsequent decarboxylation to the alcohol, but the reaction is practically complete and converted to N-succinimidyl carbonate. Phosgene that may remain after phosgenation is immediately hydrolyzed. As by-products, the mixture contains the corresponding chlorides, namely ammonium chloride, alkali metal or alkaline earth metal chlorides and optionally carbon dioxide.

At the end of the reaction, the phases are separated, the aqueous phase comprising ammonium chloride or alkali or alkaline earth metal chlorides.

The organic phase contains the desired N-succinimidyl carbonate which is readily isolated by evaporation of the solvent.

The practice of the process of the invention will be illustrated by the following examples, which are not intended to limit the scope of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

9-Fluorenylmethanol (98.1 g, 0.50 mol) is dissolved in 300 ml of tetrahydrofuran and the solution is cooled to 15 ° C. Phosgene (54.4 g, 0.55 mol) was then added with cooling over 30 minutes. The solution is then stirred for 1.5 hours at 15 ° C, completing the first stage. In a second reaction vessel, 63.3 g (0.55 mole) of N-hydroxysuccinimide, 115.1 g (1.15 mole) of potassium bicarbonate, 350 ml of water and 300 ml of tetrahydrofuran were charged. The reaction solution from the first step is then added rapidly and the mixture is stirred for 1 hour. Upon completion of the reaction, phase separation occurs. The tetrahydrofuran phase is separated and evaporated.

162 g of 9-fluorenylmethylsuccinimidyl carbonate are obtained. Yield 96% based on 9-fluorenylmethanol used. The HPLC content of the product was 98%. After leaching with isopropanol, a product with a purity of 99.9% could be obtained.

Δ-NMR (CDCl ₃ ): δ = 7.77 (d, J = 7.5Hz, 2H), 7.62 (d, J = 7.5Hz, 2H), 7.43 (t, J = 7.5 Hz, 2H), 7.36 (t, J = 7.5 Hz, 2H), 4.56 (d, J = 7.5 Hz, 2H), 4.33 (t, J = 7, 5 Hz, 1H), 2.80 (s, 4H) ppm.

Example 2

54.1 g, 0.50 mol of benzyl alcohol are dissolved in 300 ml of tetrahydrofuran. To this solution, 49.9 g (0.505 mol) of phosgene was added over 1 hour with cooling, and then the mixture was stirred at 15 ° C for 30 minutes to complete the first step.

A further reaction vessel was charged with a solution of 57.5 g, 0.5 mole of N-hydroxysuccinimide, 105.1 g of potassium bicarbonate (1.05 mole), followed by 350 mL of water and 300 mL of tetrahydrofuran. The reaction solution from the first step is then added rapidly and the mixture is stirred for a further 20 minutes. At the end of the reaction, phase separation occurs. The tetrahydrofuran phase is separated and evaporated.

120 g of benzyl succinimidyl carbonate are thus obtained. Yield 96% based on benzyl alcohol used.

@ 1 H-NMR (CDCl3): .delta. = 7.40 (s, SH), 5.32 (s, 2H), 2.82 (s, 4H) ppm.

Example 3

71.3 g, 0.50 mol of 2-chlorobenzyl alcohol are dissolved in 300 ml of tetrahydrofuran. To this solution, 54.4 g, 0.550 moles of phosgene is added over 45 minutes with cooling, and then the mixture is stirred at 15 ° C for 1 hour to complete the first step.

A solution of 57.5 g, 0.5 mole of N-hydroxysuccinimide, 115.1 g, 1.150 mole of potassium bicarbonate, 350 ml of water and 300 ml of tetrahydrofuran was prepared as a sample in another reaction vessel.

The reaction solution from the first step is then added rapidly and the mixture is stirred for 1 hour. At the end of the reaction, phase separation occurs. The tetrahydrofuran phase is separated and evaporated.

138 g of 2-chlorobenzylsuccinimidyl carbonate are thus obtained. The yield is 97% based on the starting 2-chlorobenzyl alcohol.

1 H-NMR (CDCl 3) δ = 7.3-7.5 (m, 4H), 5.43 (s, 2H), 2.80 (s, 4H) ppm.

Example 4

44.3 g, 0.25 mol of 2,4-dichlorobenzyl alcohol are dissolved in 300 ml of tetrahydrofuran. To this solution, 27.2 g, 0.272 mol of phosgene is added over 45 minutes with cooling, and the mixture is stirred at 15 ° C for 1 hour to complete the first step.

A solution of 28.8 g, 0.25 mole of N-hydroxysuccinimide, 57.5 g, 0.575 mole of potassium bicarbonate, 350 ml of water and 300 ml of tetrahydrofuran was prepared as a sample in a second reaction vessel. The reaction solution from the first step is then added rapidly and the mixture is stirred for 1 hour. At the end of the reaction, phase separation occurs. The tetrahydrofuran phase is separated and evaporated.

75 g of 2,4-dichlorobenzylsuccinimidyl carbonate are thus obtained. The yield is 94% based on the starting 2,4-dichlorobenzyl alcohol.

@ 1 H-NMR (CDCl3): .delta. = 7.27-7.45 (m, 3H), 5.40 (s, 2H), 2.84 (s, 4H) ppm.

Example 5

4-Nitrobenzyl alcohol (76.6 g, 0.50 mol) was dissolved in 300 mL of tetrahydrofuran. To this solution was added phosgene (54.4 g, 0.550 mol) with cooling over 45 minutes, and then the mixture was stirred at 15 ° C for 1 hour to complete the first step.

In a further reaction vessel, a solution of 57.5 g, 0.5 mole of N-hydroxysuccinimide, 115.1 g, 1.150 mole of potassium bicarbonate, 350 ml of water and 300 ml of tetrahydrofuran was prepared as a template.

The reaction solution from the first step was then added rapidly and the mixture was further stirred for 1 hour. At the end of the reaction, phase separation occurs. The tetrahydrofuran phase is separated and evaporated.

140 g of 4-nitrobenzylsuccinimidyl carbonate are thus obtained. The yield is 95% based on 4-nitrobenzyl alcohol.

@ 1 H-NMR (CDCl3): .delta. = 8.27 (d, J = 8.7 Hz, 2H), 7.58 (d, J = 8.7 Hz, 2H), 5.42 (s, 1H) , 2.86 (s, 4H) ppm.

Example 6

3-Phenoxybenzyl alcohol (80.1 g, 0.40 mol) was dissolved in 300 mL of tetrahydrofuran. To this solution 43.5 g (0.440 mol) of phosgene was added over 45 minutes with cooling and the mixture was stirred at 15 ° C for 1 hour to complete the first step.

In a further reaction vessel, a solution of 46.0 g, 0.4 mole of N-hydroxysuccinimide, 92.1 g, 0.92 mole of potassium bicarbonate, 350 ml of water and 300 ml of tetrahydrofuran was prepared as a template.

The reaction solution from the first step was then added rapidly and the mixture was further stirred for 1 hour. At the end of the reaction, phase separation occurs. The tetrahydrofuran phase is separated and evaporated.

127 g of 3-phenoxybenzylsuccinimidyl carbonate are thus obtained. The yield is 93% based on 3-phenoxybenzyl alcohol.

@ 1 H-NMR (CDCl3): .delta. = 7.01-8.38 (m, 10H), 5.27 (s, 2H), 2.83 (s, 4H) ppm.

Claims (2)

PATENT CLAIMS A process for the preparation of N-succinimidyl carbonates of the formula I of the formula ΠΙ o wherein Ar is as defined above, and the reaction mixture is reacted with an aqueous solution of N-hydroxysuccinimide in the presence of ammonium bicarbonate or carbonate, alkali metal or alkaline earth metal as a neutralizing agent without isolating the compound of formula m and isolating the compound of formula I from the organic phase. 2. The process according to claim 1, wherein the inert solvent is a straight, branched or cyclic ether having from 1 to 12 carbon atoms. The process according to claim 1 or 2, wherein the neutralizing agent is sodium bicarbonate, sodium carbonate, potassium bicarbonate or potassium carbonate, ammonium bicarbonate or ammonium carbonate. Process according to claim 1, characterized in that an alcohol of the general formula Π is used, in which Ar represents 9-fluorenyl, phenyl or 2-chlorophenyl. End of document at wherein Ar is 9-fluorenyl, phenyl, optionally substituted with halogen, nitro, C 1 -C 4 alkyl or trifluoromethyl, or a heteroaromatic radical having 5 or 6 ring atoms and one or two nitrogen or sulfur atoms, characterized in that an alcohol of the general formula Π is reacted Ar-CH 3 OH (Π) wherein Ar is as defined above, with phosgene in the presence of an inert, water-miscible solvent to form the chloroformic acid ester of general