MITSUNOBU REACTION OF 1,5-ANHYDRO-3,4,6-TRI-O-BENZYL-2-DEOXY-2-HYDROXYMETHYL-HEX-1-ENITOLS AND 1,5-ANHYDRO-2-DEOXY-4,6-O-PROTECTED-HEX-1-ENITOLS - A NOVEL METHOD FOR THE SYNTHESIS OF 2-C-METHYLENE GLYCOSIDES AND AN USEFUL ALTERNATIVE TO FERRIER REARRANGEMENT

A simple and convenient method for the synthesis of aryl-3,4,6-tri-O-benzyl-2-deoxy-2-methylene-hexopyranosides 5,6 and 7, glycosides which are not accessible by the conventional Ferrier rearrangement, has been described based on the Mitsunobu reaction of alcohols 3 and 4 with substituted phenols. The anomeric configurations of glycosides 5 and 6 were established by detailed NOE studies. The reaction is also successfully extended to the synthesis of phthaloyl derivative 10. A mild, neutral and non-acidic alternative to Ferrier rearrangement for the synthesis of 23-dideoxy-hex-2-enopymnosides has also been demonstrated with a variety of nucleophiles.