A 2-STEP CHEMICAL CHIROPTICAL METHOD FOR DETERMINING ABSOLUTE-CONFIGURATIONS OF ALPHA-HYDROXY ACIDS/

A general, chemical/chiroptical approach based on the CD exciton chira lity method has been developed to determine the absolute configuration of a-hydroxy acids. This approach consists of amidation of the carbox yl group with ethanolamine followed by derivatization with the hydroph obic 10,15,20-triphenylporphyrinyl-5-benzoyl chromophore to form pi,pi -bisporphyrin derivatives which undergo intramolecular stacking. The s ign of the observed bisignate couplet resulting from this stacking tin methylcyclohexane) is dictated by the preferred lower energy conforme r and reflects the absolute configuration of the stereogenic center. ( C) 1998 Published by Elsevier Science Ltd. All rights reserved.