Determination of the absolute stereochemistry of alcohols and amines by NMR of the group directly linked to the chiral derivatizing reagent

NMR experiments and calculations (PM3) indicate that the asymmetry of the s ubstrate (alcohol or amine) leads to the redistribution of the conformer po pulations of their methoxyphenylacetic acid (MPA) or methoxytrifluoromethyl phenylacetic acid (MTPA) derivatives rather than to the distortion of the c onformer geometry as was postulated by Mosher. An absolute configuration of secondary alcohols and primary amines can be determined according to the c hemical shifts of the CalphaH protons in NMR spectra of their MPA derivativ es. The CalphaH proton of the diastereomer having a greater relative popula tion of the sp form should resonate at a lower held. (C) 2001 Elsevier Scie nce Ltd. All rights reserved.