Chiral synthesis of polyketide-derived natural products. Part 6. Chemical correlation of chiral synthons, derived from D-glucose for the synthesis of erythromycin A, with chemical cleavage products the natural antibiotic

Abstract

In order to prove unequivocally the structures and configurations of the two synthesized segments, (3) and (4), for the synthesis of erythromycin A (1) from D-glucose (2), chemical cleavage of dihydroerythronolide A (5) at the lactone and the 5,6-vicinal diol positions was examined via selective protection of hydroxy groups, lithium aluminium hydride reduction, and lead tetra-acetate oxidation. The two segments derived from (5), (2R,3S,4S,5R,6R,7R)-1-hydroxy-5,6-isopropylidenedioxy-3,7-bis-(4-methoxybenzyloxy)-2,4,6-trimethylnonane (3) and (2S,3R,4S)-3,5-isopropylidenedioxy-2,4-dimethylpentanal (4), were completely identical in their spectral data with the respective synthesized segments.