Isomerisation of vitamin a

Abstract

Abstract Improved method for the isomerisation and transesterification of Vitamin A. Isomerisation of the isomeric mixture is carried out using iodine in the presence of a basic amine which functions as an improved isomerisation catalyst system. In this way the unwanted cis isomers, in particular the 9-cis isomers can be reduced to less than 5%. A wide range of solvents can be used, preferably those in which both the starting material and product are soluble. Preferred solvent system is n-hexane or pyridine. Esters of vitamin A can also be used for the process. Optimum temperature for the reaction is 50-60 deg.C for between 5 and 12 hrs. Isomeric mixtures of vitamin A containing the less active 9-cis isomer, 13-cis isomer and 11-cis and 11, 13-dicis isomers can be converted to the more active trans form thus enabling a smaller dose to be used in pharmaceutical preparations. Existing isomerisation techniques result in the production of about up to 20% of the unwanted 9-cis isomer, a disadvantage which is overcome by using the present method.

Inventors

• 👤 Anthony Kardys Joseph

Bibliographic Details