Preparation and Reactions of Racemic and Optically Active Cyanohydrins

Chiral (R)-, (S)-cyanohydrins are widespread in nature in the form of the respective glycosides and serve roughly 3000 plants and many insects as antifeedants. For the preparative organic chemist, this class of compounds offers an enormous synthetic potential for making other chiral compounds accessible. In a few instances, the pharmacological principle of a drug also incorporates a chiral cyanohydrin as constitutive structural element. The development of simple synthetic procedures for cyanohydrins, which also entail a high degree of stereoselectivity, therefore has prime importance. In this respect, chiral cyanohydrins may serve as stereochemically pure starting materials Stereoselective follow–up of (R)–and (S)–cyanohydrins lead to other important classes of compounds with stereogenic centeres. Thus, starting from (R)–cyanohydrins, (R)–2–hydroxyaldehydes, (R)–2–hydroxyketones, (1R)–2–aminoalcohols and (1R, 2S)–2–aminoalcohols are easily obtained in high optical and chemical yields by appropriate transformations of the cyano–group.cyanohydrins can also produce optically active tertiary α–hydroxycarboxylic acid