Model Study via Chelation Control in the Aldol Reaction by Kalesse

Model Study via Chelation Control in the Aldol Reaction by Kalesse 

Double stereodifFerentiating aldol reactions with methyl ketone 37 

This is a very useful example in connection tvith the model studies to approach the epothilones. 

As a result of a chelation-controlled aldol reaction exclusive formation of compound 43 tvith the desired 6(R),7(S),8(R)-triad tvas observed. The structure has been confirmed by X-ray analysis after transformation to a crystalline six-membered lactone. In their macro-lactonizsation strategy to synthesize epothiione B Nicolaou et al. used the same ketone 41 in an aldol reaction vith aldehyde 19. The diastereoselectivity in the aldol addition vas only moderate, giving a ratio of 3 1 in favor of the natural epothiione configuration [33]. 

DifTerent Aldol Strategies Mulzer s Total Syntheses of Epothilones B and D 

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