Characterization of sarcosylsarcoursodeoxycholic acid formed during the synthesis of sarcoursodeoxycholic acid

This report describes the isolation of sarcosylsarcosine conjugate of ursodeoxycholic acid (UDCA) formed during the synthesis of sarcoUDCA by the mixed anhydride method. The compound was characterized by its chemical ionization mass spectrum. The diamino acid conjugate was formed only when the free amino acid was used for conjugation. This was confirmed by the isolation of glycylglycoUDCA during the conjugation of UDCA with free glycine but not with glycine ethyl ester hydrochloride. Pure sarcoUDCA was prepared by conjugation of UDCA with sarocisine methyl ester hydrochloride while sarcoUDCA on further reaction with the protected sarcosine derivative gave pure sarcosylsarcoUDCA in 52% yield.