DDQ-INDUCED, ANOMERIC SPECIFIC, AND DIASTEREOSELECTIVE BENZYLIC GLYCOSIDATION - A NOVEL-APPROACH TO HETEROCYCLIC ANTHRACYCLINE ANTIBIOTICS

A novel and efficient method for the oxidative glycosidation at the he terosubstituted benzylic positions with 2,3-dichloro-5,6-dicyanobenzoq uinone (DDQ) is described. The reaction is stereospecific with 3-subst ituted isochromans and isothiochroman, as well as diastereoselective w ith non-3-substituted isochromans. The glycosidation with a mixture of alpha- and beta-anomeric free sugars gives alpha-glycosides with abso lute stereochemical control on the anomeric center. The synthetic util ity of this novel methodology is demonstrated by a short, efficient, a nd stereoselective total synthesis of heteroanthracycline antitumor re agents.