Anisotropic and hydrogen bonding effects in phenylglyoxamides and mandelamides: theoretical and NMR conformational evaluation.

Interesting anisotropic effects were observed for phenylglyoxamides and their respective mandelamides. Such effects were observed in experimental 1H and 13C NMR (in CDCl3, CD3OD, and DMSO-d6 solvents) and in some cases with good correlation to theoretical 1H and 13C NMR DFT–GIAO (B3LYP/6-311 + + G**//B3LYP/6-31G*) calculations. A systematic conformational analysis of these compounds was performed in a two-step methodology, using PM3 and DFT (B3LYP/6-31G*) calculations; with good accomplishment and computational time economy. It was observed that intramolecular hydrogen bonding plays a significant role in the conformation of such compounds. Finally, a geminal nonequivalence of an NCH2 moiety, in one of the alkyl side chain (R1 = R2), was found for the tertiary mandelamides studied. Copyright © 2008 John Wiley & Sons, Ltd.