Experiments Directed Towards the Synthesis of Anthracyclinones. XXIV. Homochiral Intermediates for Vineomycin Syntheses

Abstract

Homochiral intermediates suitable for the synthesis of vineomycins have been prepared by a titanium-mediated addition of an enolate of (-)-menthyl acetate to the furano ketones (12) and (13). The absolute configurations of the menthyl butanoates (14) and (15) have been established by comparison of their ¹H n.m.r. spectra in the presence of Eu ( hfc )₃ with those of the corresponding fridamycin derivatives (20) and (21). ¹H 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 confirmed the configurations. The use of chiral sulfoxides for the construction of the butanoate side chain was thwarted when (28) could not be desulfurized, and when attempts to add (27) to the trimethoxyanthracene (29) were unsuccessful.