ASYMMETRIC ACETATE ALDOL REACTIONS IN CONNECTION WITH AN ENANTIOSELECTIVE TOTAL SYNTHESIS OF MACROLACTIN-A

Asymmetric aldol-like reactions of cinnamaldehyde, dienal 3 (fragment C7-C12 of macrolactin A), and dienal 4 (fragment C15-C24) with (i) chi ral acetylthiazolidinethione-derived enolates, (ii) chiral boron enola tes, and (iii) silyl enolates in the presence of chiral titanium-2,2'- dinaphthol complexes are compared. Use of the thiazolidinethione auxil iary and TiCl4 shows practical advantages; e.g., C5-C12 fragment 7 has been isolated enantiomerically pure in 74% yield. Copyright (C) 1996 Elsevier Science Ltd