Synthesis of CentralChirality-Containing Triarylmethanols and Triarylmethyl Radicals withExtraordinarily Stable Configurations

Triarylmethanol adopts a propeller-shaped conformation with either right-handed (P) or left-handed (M) configuration. Herein, new triarylmethanols with two chiral centers were obtained via introduction of two cis-hydroxyl groups on the side chains, affording four stereoisomers. These four stereoisomers were easily separated by silica gel column chromatography into two pairs of propeller–shaped enantiomers as shown by NMR and X-ray crystallographic studies. HPLC studies showed that the configuration of the hydroxyl-bearing triarylmethanols is much more stable than the bulky tert-butyldimethylsilyl (TBS) protected precursors, inconsistent with the general strategy in which the steric repulsion is largely responsible for the configurational stability. Similarly, two hydroxyl-bearing TAM radicals also exhibit excellent configurational stability and are thus separable by CS-HPLC into four stereoisomers. Interestingly, both helical chirality from tri-aryl group (M or P) and central chirality (R and S) on the si...