Prelog-Cram rule

Bakers yeast is used almost exclusively for reduction, principally of ketones, by a dehydrogenase which usually follows the Prelog-Cram rule. As with chemical reductions, highest enantioselectivity obtains with aromatic aldehydes and aryl methyl ketones. /3-Keto esters arc also reduced with high canantiosclectivity by yeast. Some j8-kcto acids can also be reduced efficiently to (R)-jS-hydroxy acids. 

A potentially useful extension of the Cram s rule is the asymmetric induction provided by a remote ester (Prelog s rule). ... 

Application of this condensation to aldehydes with an a-chiral center gives rise to two chiral centers, the relative stereochemistry of which can be related to the Prelog-Cram selectivity rule. Such a reaction was used for a short stereoselective synthesis of... 

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