Journal of the American Chemical Society, Vol.115, No.26, 12533-12544, 1993
The Cd in-Situ Complexation Method as a Tool for Determination of Absolute-Configurations of Cottonogenic Derivatives
An easy and versatile method has been developed for the generation of enhanced Cotton effects (CEs) from optically active substances that are weakly absorbing in the accessible wavelength range. This method involves the in situ interaction of chiral carboxylic acids, alpha-amino acids, amino alcohols, ephedrine isomers, and polynucleic acids with trinuclear metal complexes : [M3O(O2CCH3)6L3]n+, where M = Fe, Cr, Mn, Rh, Ru, etc., L = water or pyridine, and n = 0 or 1. These derivatives, with their conformational flexibility either reduced or totally restricted, give rise to CEs. Semiempirically based helicity rules and newly established sector rules have been applied for the correlation of the CEs with the absolute configurations.