Parlaying C–O chirality into C–C chirality: improving the cost/benefit ratio of carbohydrate templates
Use of sugars as chirons for complex carbocyclic targets requires that C–O chirality be transmuted into C–C chirality. The cost/benefit ratio in such syntheses is one index of efficiency. For example, the process involving oxidation of a secondary alcohol followed by methylenation and hydrogenation gives, at best, a 1:1 ratio. The aim of lowering this ratio has been a feature of our synthetic studies, some of which are described in this article. Among other things, the studies show that the stereochemistry of pendant, off-template mixed acetals can direct the stereo- and regio-selectivity choices (e.g. 5-exo-trig versus 6-exo-trig) in radical cyclization reactions.