PREPARATIVE SYNTHESIS OF THE COREY CHIRAL CONTROLLER FOR ENANTIOSELECTIVE DIHYDROXYLATION OF OLEFINS

A five-step synthesis of both enantiomers of di(2,4,6-trimethylbenzyla mino)-1,2-diphenylethane, i.e., Corey (R,R)- and (S,S)-controllers for enantioselective dihydroxylation of olefins by osmium tetroxide, star ting from alpha,alpha'-diphenylglyoxime, has been developed. The key o perations in the synthesis are the optical resolution of intermediate rac-1,2-diamino-1,2-diphenylethane into two enantiomers using only (R, R)-tartaric acid and the subsequent enhancement of the enantiomeric pu rity to >98% by crystallizations of the corresponding Schiff's bis-bas es. Analysis of the enantiomeric purity of the controllers can be easi ly performed using H-1 NMR spectra of their salts with -alpha-methoxy- alpha-(trifluoromethyl)phenylacetic acid (Mosher R-acid).