Regioselective enzymatic acylation of polyhydroxylated sesquiterpenoids

Regioselective acetylation of some protoilludane sesquiterpenes has been performed using a set of commercially available lipases. While esterification of the illudane “Illudine S” (1) gave the expected derivative mono-acetylated at the primary C(15)-OH, acylation of the protoilludane “Tsugicoline A” (2) and of its derivatives 3 and 4 gave different products depending on the lipase used. Preferential regioselective esterification of the less chemically reactive secondary C(6)-OH in 4 and of the tertiary C(5)-OH in 3 was obtained by action of Candida rugosa lipase and lipase A from Aspergillus niger, respectively.