Absolute stereochemistry of unusual biopolymers from Ascomycete culture LL-W1278: Examples that derivatives of (S)-6-hydroxymellein are also natural fungal metabolites

Abstract

The new linear polyesters, W1278-A, B, and C, were isolated from culture extracts of a freshwater Ascomycete fungus. Their structures were elucidated on the basis of spectroscopic analyses and chemical transformations, with the absolute configuration established by the circular dichroism (CD) method using (R)-(-)-6-hydroxymellein as reference. Unexpectedly, W1278-A, B, and C contain (S)-6-hydroxymellein residues as concluded from the display of the opposite ellipticity than that of known (3R)-(-)-3,4-dihydro-6,8-dihydroxy-3- methylisocoumarin as revealed by CD. © 2005 Wiley-Liss, Inc.