Synthetic Study of Pradimicns, Antiviral Antibiotics Possessing the Binding Abilities to Oligosacchrides

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The pradimicin-benanomicin antibiotics constitute a new class of natural products with a benzo[a]naphthacenequinone core wkh an amino acid and a disaccharide.They show anti-fungal and anti-HIV activities, which are related to the selective binding abilities to mannose-rich oligosaccharides, e.g. the mannane surface of fungi or gp 120 of HIV. The unique structure as well as the significant biological activities led me to undertake the synthesis of this class of compounds.The most intriguing challenge among the synthetic issues is the control of the vicinal diol stereogenicities at the corner of the pentacyclic skeleton comprises, to which we explored the possible use of intramolecular pinacol coupling of bis-aldehyde. Along these lines, we found that this reaction is useful for the above issue.The SmIィイD22ィエD2-mediated pinacol coupling of biphenyl o, o'-dialdehyde was found to proceed stereo selectivelly and gave only trans diol, which enabled us to achieve the synthesis of the trans diol structure of B ring as diastereomerically pure form. Furthermore, the reaction proved to proceed stereospecifically, thereby enabling the full transmission of the axial chirality into the two central chiralities. Thus, we studied the stereoselective and -specific pinacol coupling of bis-aldehyde, providing the requisite trans-diol in enantio- and diastereomerically pure form, which served as a basic strategy for the total synthesis of the pradimicin-benanomicin class antibiotics.Total synthesis of the pradimicinone (benanomicinone), the common aglycon of the class of natural products, based on the above mentioned pinacol cyclization, has been achieved.