SYNTHESIS AND BIOLOGICAL EVALUATION OF SULFUR ISOSTERES OF, THE POTENT INFLUENZA-VIRUS SIALIDASE INHIBITORS 4-AMINO-4-DEOXY-NEU5AC2EN AND 4-DEOXY-4-GUANIDINO-NEU5AC2EN

The synthesis of the thioisosteres of 4-amino-4-deoxy-Neu5Ac2en (16) a nd 4-deoxy-4-guanidino-Neu5Ac2en (17) has been achieved. These compoun ds have been found to be as bioactive as the corresponding oxygen anal ogues. The preparation of the key intermediate, cetyl-2,6-anhydro-3,4, 5-trideoxy-2'-methyl-6-thio- methyl D-glycero-D-talo-non-2-enonato)[5, 4-d]oxzole 13, has been achieved from ,6-O-isopropylidene-3-thio-alpha ,beta-D-mannofuran 8 in four steps in 43% overall yield.