BIOTRANSFORMATION OF 6-BETA-EUDESMANOLIDES FUNCTIONALIZED AT C-3 WITH CURVULARIA-LUNATA AND RHIZOPUS-NIGRICANS CULTURES

A series of biotransformations of 6-beta-santonin and its derivatives with functions at C-3, were carried out with Curvularia lunata and Rhizopus nigricans cultures. Rhizopus nigricans was more active in the biotransformation process against these substrates. The biotransformation of 6-beta-santonin yielded its 2-alpha-hydroxy-1,2-dihydro derivative. The biotransformation of ketones at C-3 obtained by partial or total hydrogenation of double bonds in ring A led to 3S alcohols. Incubation of the 3S-hydroxyl-4S-13S-6-beta-eudesmanolide with Rhizopus nigricans produced epimerization at C-4 and hydroxylation at C-8, C-1 or C-4, in decreasing order. This epimerization is probably produced with the participation of the hydroxyl group at C-3. Microbial functionalization at C-8 can provide access to the synthesis of 8,12-eudesmanolides.