Asymmetric routes to substituted piperidines

An overview of the main asymmetric routes to substituted piperidines is presented. A wide range of synthetic strategies have been developed, because of the ubiquitous nature of the piperidine sub-unit in natural products, and because of the biological properties of natural and synthetic piperidine derivatives. This review concentrates on general methodologies that provide enantioselective routes to substituted piperidines, but also includes some specific target syntheses that illustrate the power of the methods that have been developed. The three approaches that have been most successful are: the use of the chiral pool, especially amino acids; the use of reagents that utilise a chiral catalyst; and the use of chiral auxiliaries in the asymmetric formation or derivatisation of the piperidine ring.