THE TOTAL SYNTHESIS OF AB3217-A, A NOVEL ANTIMITE SUBSTANCE, VIA INTERMOLECULAR ETHERIFICATION AND INTRAMOLECULAR GLYCOSYLATION

The first total synthesis of AB3217-A has been achieved. The deacetyla nisomycin unit, (3S,4S,5R)-3-benzyloxy-1-(benzyloxycarbonyl)-5- [(1R)- 1-hydroxy-1-(4-methoxyphenyl)methyl]-4- (2-tetrahydropyranyloxy)-pyrro lidine (18), was prepared from dimethyl L-tartrate by a stereoselectiv e pyrrolidine-ring formation and a stereoselective reduction of phenyl ketone as the key steps. The lithium alkoxide of 18 was coupled with the D-xylofuranose unit, phenyl luoromethanesulfonyl-1-thio-alpha-D-xy lofuranoside which was prepared from 1,2: 5,6-di-O-isopropylidene-alph a-D-glucofuranos via an intermolecular etherificaiton. The resulting c oupling product was subjected to de-O-tetrahydropyranylation and an in tramolecular glycosylation to ord4,12,13-tribenzyl-6-(benzyloxycarbony l)AB3217-A (30). Final deprotection of 30 furnished AB3217-A.