A new method for establishment of absolute configurations of organic compounds by use of axially chiral reagents - Axial chirality method

A new method to establish the absolute configurations of organic compounds is reviewed. This method is designated "axial chirality method" because it uses axially chiral biaryls as chiral auxiliaries. Chiral secondary alcohols, alpha-chiral primary amines and alpha-chiral carboxylic acids are derivatized with the above reagents. The absolute configurations of original compounds are correlated to the Delta delta values, which are defined as Delta delta=delta aS-delta aR for each proton of the diastereomeric derivatives. Some models are described to explain the observed proton shifts and the signs of Delta delta s. In certain cases, NOEs were observed between the protons of the reagent's moiety and those of substrate's one. The absolute configuration of a sterically hindered tertiary alcohol was determined by this new method using the Delta delta values and NOE correlations. One new C-centrochiral reagent was also presented. Versatility and limitation of this method are discussed.