Chlorine, an atom economical auxiliary for asymmetric aldol reactions
作者:Shira D. Halperin、Robert Britton
DOI:10.1039/c3ob27462d
日期:——
An auxiliary strategy has been developed for asymmetricreactions of aldehydes in which the auxiliary itself is not chiral, but a single chlorine atom introduced via organocatalytic α-chlorination. The stereodirecting influence of the chlorine atom is then exploited prior to its removal by radical reduction. This strategy is demonstrated in the synthesis of several aldols (92–99% ee) and the natural
Direct catalytic enantioselective cross aldol-typereaction of an acetate surrogate was developed using Cu alkoxide-chiral phosphine complexes as catalysts. Chemoselective activation and deprotonation of the donor substrate (acetonitrile) by the soft metal alkoxide in a strongly donating solvent (HMPA) are key to success in this reaction. Useful chemical yields and promising enantioselectivities are
Biocatalytic strategy toward asymmetric β-hydroxy nitriles and γ-amino alcohols
作者:Randall W. Nowill、Trisha J. Patel、David L. Beasley、Jose A. Alvarez、Elizah Jackson、Todd J. Hizer、Ion Ghiviriga、Scott C. Mateer、Brent D. Feske
DOI:10.1016/j.tetlet.2011.03.009
日期:2011.5
A library of 20 bakers’ yeast reductases, that are overexpressed in Escherichia coli, were screened against a variety of β-keto nitriles. Enzymes from the aldose reductase and the short chain dehydrogenase family displayed activity toward these substrates. All of the seven substrates were reduced with high enantioselectivities and in some cases both antipodes could be synthesized in high ees. These