Betulin esters with coumarin-3-carboxylic and 3,4,5-trimethoxybenzoic acids

Direct esterification of betulin with coumarin-3-carboxylic or 3,4,5-trimethoxybenzoic acid led to betulin-28-esters and betulin-3,28-diesters. The betulin-3-esters were synthesized through 28-O-protection, esterification and deprotection steps using betulin as a starting material.