Microbial Transformations of the Taxan Ring of 10-DAB by Some Strains of the Fungus Curvularia lunata: Formation of the Bis-abeotaxanes Wallifoliol and 4-Deacylwallifoliol

The fermentation of 10-deacetylbaccatine III (10-DAB) (1) with Curvularin lunata afforded 4-deacylwallifoliol (4) and wallifoliol (5), the only natural taxoid with the unusual 5/6/6/6/4 ring system. The X-ray structure of compound 4 is reported. The skeletal rearrangements induced by the microbial enzymatic systems are also discussed.