AN ALTERNATIVE INTERPRETATION OF THE HETCOR NMR-SPECTRA OF POLY(LACTIDE)

An alternative to the assignments proposed recently by Chishohn et al. for the H-1 and C-13 NMR resonances of poly(lactide) based on their H ETCOR spectra is presented; we find that the HETCOR spectra are consis tent with older assignments of the tetrad and hexad stereosequence res onances in the H-1 and C-13 NMR spectra and we believe that the influe nce of adjacent chiral units on the NMR chemical shift extends asymmet rically and is opposite in the case of H-1 and C-13 nuclei; this is in contrast to the assumption that the observed chiral repeat unit for a ny particular stereosequence resonance is the same for H-1 and C-13 NM R spectra as used by Chisholm et al. in their analysis.