How is 4-KETO 13-CIS-RETINOIC ACID METHYL ESTER (CAS: 71748-57-7) typically synthesized?

4-KETO 13-CIS-RETINOIC ACID METHYL ESTER is typically synthesized through a series of steps involving the modification of retinol. The reaction involves the oxidation of retinol to retinal, followed by the isomerization of 13-cis-retinal to 13-cis-retinol, and finally the formation of the methyl ester through esterification. This process often utilizes chemical reagents such as iodine and sulfuric acid, and requires careful control of reaction conditions to achieve high yields and selectivity.