Regio-selective acylation of biologically important iridoid glycosides by Candida antarctica lipase

Lipase catalyzed regio-selective acylation of five iridoid glycosides viz., picroside I&II, catalpol, agnuside and negundoside in the presence of various acyl donors such as vinyl acetate and p-nitrophenyl alkanoates was studied. The regio-selectivity of enzymatic acylation and yields were found to vary amongst different substrates. Monoacylated products were isolated with all the substrates under scrutiny indicating high regio-selective nature of such transformations. A series of acyl esters of picroside-I, picroside-II, catalpol, agnuside and negundoside have been synthesized by this enzymatic trans-esterification methodology.