Method for producing N-retinoylcysteic acid alkyl ester
A method for producing derivatives of N-retinoylaminoalkane sulfonic acid, the method comprising providing retinoic acid, chloroformate, aminoalkanesulfonic acid selected from the group consisting of cysteic acid and alkyl ester thereof, cysteinesulfinic acid and alkyl ester thereof, homocysteic acid and alkyl ester thereof, homocysteinesulfinic acid and alkyl esters thereof, taurine and derivatives thereof, and an organic solvent, and a base, mixing said components under substantial absence of oxidizing compounds thereby forming a reaction mixture comprising a liquid phase, wherein the liquid phase is one phase and the derivatives of N-retinoylaminoalkane sulfonic acid are formed in said liquid phase.
1. A method for producing derivatives of N-retinoylaminoalkane sulfonic acid, the method comprising providing
i) a first solution comprising an aminoalkane sulfonic acid selected from the group consisting of cysteic acid and alkyl ester thereof, cysteinesulfinic acid and alkyl ester thereof, homocysteic acid and alkyl ester thereof, homocysteinesulfinic acid and alkyl esters thereof, taurine and derivatives thereof, an alcohol selected from aliphatic alcohols comprising 1 to 4 carbon atoms and a first base selected from trialkylamines,
ii) a second solution comprising a retinoic acid, a chloroformate, an aprotic solvent and a second base,
adding first and second solutions in any order to a reaction vessel thereby forming a reaction mixture comprising at least a liquid phase being one phase, mixing said reaction mixture, wherein retinoic acid, aminoalkane sulfonic acid and chloroformate are all soluble and present in said liquid phase and the derivatives of N-retinoylaminoalkane sulfonic acid are formed in said liquid phase under conditions characterised as being substantially free from oxidizing compounds.
2. The method according to claim 1 , wherein the derivatives of N-retinoylaminoalkane sulfonic acid are selected from N-(13-cis-retinoyl)-cysteic acid alkyl ester and N-(all-trans-retinoyl)-cysteic acid alkyl ester, the retinoic acid is selected from 13-cis-retinoic acid or all-trans-retinoic acid, and the aminoalkanesulfonic acid selected from cysteic acid alkyl ester.
3. The method according to claim 1 , wherein the alcohol is selected from the group consisting of methanol or ethanol or a mixture thereof.
4. The method according to claim 1 , wherein the aprotic solvent is tetrahydrofuran.
5. The method according to claim 1 , wherein the chloroformate comprises an aliphatic group comprising from 2 to 6 carbon atoms.
6. The method according to claim 1 , wherein the chloroformate is iso-butyl chloroformate.
7. The method according to claim 1 , wherein the second base is an amine.
8. The method according to claim 7 , wherein the amine is trialkylamine, suitably triethylamine.
9. The method according to claim 1 , wherein the single phase is one phase without phase separation.
10. The method according to claim 1 , wherein the derivatives of N-retinoylaminoalkane sulfonic acid are purified using preparative chromatography.
11. The method according to claim 1 , wherein the alkyl group of the derivatives of N-retinoylaminoalkane sulfonic acid and the alkyl of aminoalkane sulfonic acid comprises from 1 to 3 carbon atoms.
12. The method according to claim 11 , wherein the alkyl group is methyl.