EXPERIMENTS DIRECTED TOWARDS THE SYNTHESIS OF ANTHRACYCLINONES .24. HOMOCHIRAL INTERMEDIATES FOR VINEOMYCIN SYNTHESES

Homochiral intermediates suitable for the synthesis of vineomycins hav e been prepared by a titanium-mediated addition of an enolate of (-)-m enthyl acetate to the furano ketones (12) and (13). The absolute confi gurations of the menthyl butanoates (14) and (15) have been establishe d by comparison of their H-1 n.m.r. spectra in the presence of Eu(hfc) (3) with those of the corresponding fridamycin derivatives (20) and (2 1). H-1 n.m.r. comparisons of the methyl esters (16), (17), (22) and ( 23) in the presence of (R)-2,2,2-trifluoro-1-(9-anthryl)ethanol confir med the configurations. The use of chiral sulfoxides for the construct ion of the butanoate side chain was thwarted when (28) could not be de sulfurized, and when attempts to add (27) to the trimethoxyanthracene (29) were unsuccessful.