Molecular mechanics (MM3) study of the conformations of ethyl esters of diastereoisomeric 3-substituted 4,4,4-trichloro-2-cyano-butanoic acids

Molecular mechanics calculation (MM3 force field) were used to study the co nformations of diastereoisomeric pairs of ethyl esters of 3-substituted 4,4 ,4-trichloro-2-cyano-butanoic acids in order to test an assumption from H-1 NMR spectra about their preferred conformations. On the basis of the most probable preferred conformation in each case, an assignment of the relative configurations of these newly synthesized compounds was made in the earlie r study. The present computed most favorable conformations are in accord wi th the earlier qualitative considerations in all cases, thus validating the assignment of the configurations of the diastereoisomers made previously.