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Synfacts 2007(10): 1100-1100  
DOI: 10.1055/s-2007-969002
Organo- and Biocatalysis
© Georg Thieme Verlag Stuttgart · New York

syn-Selective Organocatalytic Aldol Reactions of Dihydroxyacetone Equivalents

Contributor(s): Benjamin List, Kristina Zumbansen
N. Utsumi, M. Imai, F. Tanaka, S. S. V. Ramasastry, C. F. Barbas, III*
The Scripps Research Institute, La Jolla, USA
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Publication History

Publication Date:
07 November 2007 (online)

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Significance

A syn-selective aldolization based on protected dihydroxyacetones and monohydro­xyacetones is reported. After several catalyst screenings O-t-Bu-l-Thr (1) and O-t-Bu-l-Thr(NHTf) (2) turned out to be the best catalysts. For further optimizations catalyst 1 was used. The best results were found with NMP as solvent and 3 vol% of water as an additive. This reaction shows good chemical yields and high stereoselectivity for aromatic aldehydes (dr up to 7:1 and up to 98% ee), but the reaction time is between one and seven days. Nevertheless, for glyoxalic acid-based acceptors poor yields, enantio- and diastereo­selectivities were obtained, whereas the methoxyacetal of glyoxal gave good results (71% yield, dr = 5:1, 97% ee). The absolute configuration was determined by synthesizing d-fructose from TBS-protected dihydroxyacetone and d-glyceraldehyde.