The pluramycins constitute a class of antitumor antibiotics with an anthrapyrone chromophore with two amino sugars attached through the C-glycoside linkages. These compounds exhibit antitumor activity by specific DNA alkylation with high sequence recognition. Considerable attention has been centered at the synthesis of these compounds, where two basic problems must be addressed, (1) bis-C-glycosylation and (2) the selective construction of anthra[1,2-b]pyrone chromophore. This presentation will deal with the total synthesis of the saptomycin B. Sc(OTf)_3-promoted C-glycosylation of tricyclic bisphenol 15 with vancosaminyl acetate 2 proceeded in a regioselective manner at C7 in high yield. Further reaction with angolosaminyl acetate 4 under the similar conditions proceeded at C5 to give bis-C-glycoside 13 possessing the two amino sugar moieties at the requisite positions. This bis-C-glycoside was derived to ynone 12 via the aldol addition to chiral, optically active ynal 14. Treatment of 12 with K_2CO_3 in Me0H cleanly promoted the pyranone formation, and the following three-step oxidation gave anthraquinone 32. We are now examining the final deprotection toward the total synthesis of saptomycin B.
