PHYLLANTHOSIDE PHYLLANTHOSTATIN SYNTHETIC STUDIES .8. TOTAL SYNTHESIS OF (+)-PHYLLANTHOSIDE - DEVELOPMENT OF THE MITSUNOBU GLYCOSYL ESTER PROTOCOL

The first total syntheses of the antineoplastic glycoside (+)-phyllanthoside (1) and the parent disaccharide (-)-phyllanthose (5) have been achieved. Stereoselective Koenigs-Knorr coupling of two 6-deoxyglucose derivatives, bromide 54 and alcohol 55, generated the uncommon 1' --> 2-beta-glycosidic linkage of (-)-phyllanthose. A stereochemically convergent Mitsunobu reaction of protected disaccharide 87 with aglycon carboxylic acid 80, prepared via asymmetric synthesis, then led to 1 of high enantiomeric purity. The Mitsunobu procedure comprises an efficient general method for stereospecific assembly of beta-glycosyl esters.