STEREOSPECIFIC SYNTHESIS OF AMINOSUGAR ANTIBIOTICS

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The overall goal of this study will continue to be the development of new strategies and synthetic methodologies for the stereocontrolled assembly of structurally complex aminosugar (nucleoside) antibiotics which are relatively inaccessible via traditional carbohydrate manipulation. This broad classification encompasses a wide variety of naturally occurring substances whose collective medicinal properties span the spectrum of biological activity. Representative targets for this phase of the study include the miharamycins, the albomycins, and the ezomycin complex - all of which are characterized by highly unusual monosaccharide residues. None of these natural products have yet been synthesized. A unifying structural feature upon which we will focus is the incorporation of stereodefined vicinal aminoalkoxide moieties into these atypical sugar structures. Both "unidirectional" and "bidirectional" chain elongation strategies will be employed as required for each target. The stereocontrolled assembly of systems such as these starting from aminoacid derived chiral synthons will be developed building on results obtained in our laboratory during the previous 3-year grant period. In this context we also plan to complete an ongoing study which systematically examined additions to differentially protected beta-hydroxy-alpha-aminoaldeydes. The ability of these substrates to exert diastereofacial control during nucleophilic additions via 1,2-asymmetric induction will be explored systematically. Success in these endeavors will provide valuable methodology that should be applicable to a number of related synthetic problems and may shed light on various aspects of the asymmetric induction process as well.