Coumarin-Containing Chiral Discriminating Agents. VII. New Crystalline ¹H-NMR Enantiomeric Excess Determination Reagent for Alcohols and Amines, (R)-(-)- and (S)-(+)-O-Coumarinylmandelic Acids

Abstract

The Mitsunobu reaction of commercial 4-hydroxycoumarin with both (R)-(-)- and (S)-(+)-tert-butyl mandelates derived from commercial enantiopure mandelic acids furnished (S)-(+)- and (R)-(-)-tert-butyl O-coumarinylman-delates which were, then, treated with trifluoroacetic acid to give novel crystal-line optically pure (S)-(+)- and (R)-(-)-O-coumarinylmandelic acids [SCMOH and RCMOH], respectively in good overall yields. Diastereotopic nonequivalence ¹H-NMR examination of the resultant esters and amides without any racemization or kinetic resolution by way of a Steglich's procedure (a DCC-DMAP method) has proved each acid to be a useful, efficient and reliable chiral derivatizing agent for the enantiomeric excess determination of chiral alcohols and amines.