Stoichiometric asymmetric processes

摘要

This article covers the use and application of stoichiometricnasymmetric processes for the whole of the 1999 calendernyear. The review focuses on the development of synthetic protocolsninvolving the stoichiometric use of chiral reagents andnauxiliaries. In particular, since the ultimate aim of any newnpiece of asymmetric methodology should be to use it in synthesis,nI have tried to review the tried and trusted methodsnas well as identifying methods that have wider potential andnapplication for the future. I have excluded stereoselective processesnin which an existing chiral centre (often from the chiralnpool) is incorporated in the final target structure and I have alsonchosen to ignore “chiral auxiliary” methods where the auxiliarynis never removed at the end of the synthesis. Thus, the materialncontained herein is a personal selection of the offerings of 1999.nThe review is split into three main sections. Using examplesnfrom 1999, Section 2 provides an overview of the surprisinglynfew chiral reagents and auxiliaries that are most widely usednin total synthesis. It is intended that this selection will allow thenreader to update his/her own teaching and research referencesnon chiral auxiliaries and reagents as well as highlighting thenmost important methods. The new discoveries as well as thenimprovements to previously introduced methods in the areasnof chiral auxiliaries and chiral reagents are reviewed in Sectionsn3 and 4 respectively. I have not tried to explain the sense ofninduction but have simply provided a representative examplenand have tried to identify where examples are of limited scope.