Regioselective alcoholysis of silybin A and B acetates with lipases

Large screening identified lipase AK to be capable of the selective deacetylation of pentaacetyl silybins A and B to yield 3,5,20,23-tetra-O-acetyl-silybins A and B, and 3,20,23-tri-O-acetyl-silybins A and B, respectively. Deacetylation occurred at phenolic OH groups, only. These new compounds prepared from the optically pure silybins can serve as new stereochemically pure synthons for selective silybin modifications. (C) 2011 Elsevier B.V. All rights reserved.