C-glycosyl juglone in angucycline synthesis: Total synthesis of galtamycinone, common aglycon of C-glycosyl naphthacenequinone-type angucyclines

A two-step access to C-glycosyl juglones, 16 and 17, useful intermediates toward the angucyclines, either benz[a]anthraquinone-type or naphthacenequinone-type, has been developed based on (1) the O-->C-glycoside rearrangement and (2) the regioselective cycloaddition of alpha-alkoxybenzyne and alpha-oxyfuran. The first total synthesis of galtamycinone (2), the common aglycon of naphthacenequinone-type angucyclines, has been achieved by utilizing 17 as the key intermediate. (C) 1997 Elsevier Science Ltd.