Total Syntheses of BE-12406 A and Its C(8)-Vinyl Analog

AbsIrac: -Total syntheses of BE-12406 A (3a) and i u C(8)-vinyl analog (3c) are described.The key step is the selective 0-glycosylation of naphthol (4 )with L-rhamnopyranosyl fluoride (5) by employing Cp2HfCb-AgC104 in fluorobenzene at -20 O C in the presence of a hindered base, 2,6-di-r-butyl-4-methylpyridine (12).affording 0-glycoside (11) in good yield. RESULTS AND DISCUSSIONSynthetic plan: We expected that the synthetic strategy of the gilvocarcins4b would be basically applicable to the synthesis of these compounds.Considering the convergency, BE-12406 A (3a) was divided into three readily available components, naphthol (4).L-rhamnopyranosyl fluoride (5), and benzoic acid (6) (Scheme 1).According to the literature procedures, 45 and 56 were prepared from commercially available juglone (two steps) and L-rhamnose (four steps), respectively. Scheme 1BnO .