Synthesis of Macrolide Antibiotics. IV. Stereoselective Syntheses of the 3-O-Methyl and the 11-O-Methyl Derivatives of the C(1)-C(6) Segment of Erythronolides A and B and the C(9)-C(15) Segment of Erythronolide A, Respectively

Sa？etak By appropriate dissection of the macrocyclic lactone ring of methymycin erythromycins A and B, picromycin and narbomycin, carbohydrate-like structural segments were obtained. The finding that the anomeric configuration of a glycopyranoside effectively controls the stereochemistry of various addition reactions to sp' (C=O and C=C) carbon atoms of a glycopranoside ring led to the development of a general stereoselective approach for the synthesis of the chiral carbon framework of the polyoxomacrolide aglycones of methymycin, erythromycin A and B, picromycin and narbomycin. Stereoselective synthesis of methyl 2,4,7-trideoxy-2-C, 3-0, 4-C-tri-methyl-~-L-ido-heptopyranosid-6-ulose and methyl 2,6,7-trideoxy-2-C, 3-0, 4-C-trimethyl-a-D-glucoheptopyranoside, representing the 3-0-methyl and the 11-0-methyl derivatives of the C(1)-C(6) segment of erythronolides A and B and the C(9)-C(15) segment of erythronolide A, respectively, is described