SYNTHETIC STUDIES OF THE TUNICAMYCIN ANTIBIOTICS - PREPARATION OF (+)-TUNICAMINYLURACIL, (+)-TUNICAMYCIN-V, AND 5'-EPI-TUNICAMYCIN-V

A concise synthetic route to the tunicamycin antibiotics is described, illustrated by the preparation of (+)-tunicamycin-V (1-V). Key features of the synthesis include (1) the development and application of a silicon-mediated reductive coupling of aldehydes and allylic alcohols to construct the undecose core of the natural product and (2) the development of an efficient procedure for the synthesis of the trehalose glycosidic bond within the antibiotic. These innovations allow for the coupling of a uridine-derived aldehyde fragment with a performed trehalose-linked disaccharide allylic alcohol to form the carbohydrate core (1) of the natural product in a highly covergent manner. The resultant amino polyol is a versatile intermediate for the synthesis of any of the homologous tunicamycin antibiotics.