Assignment of the 1H n.m.r. spectrum of heptamethyl dicyanocobyrinate in chloroform solution by two-dimensional 13C/1H chemical shift correlation spectroscopy

Abstract

The¹H n.m.r. chemical shifts of the vitamin B₁₂ derivative heptamethyl dicyanocobyrinate (‘cobester’) in CDCl₃ have been determined by two-dimensional ¹³C/¹H chemical shift correlation spectroscopy at 75/300 MHz. For reasons of sensitivity a pulse scheme was employed which eliminates homonuclear spin-spin coupling in the F₁ dimension between protons bonded to different carbon atoms. Large differences in ¹H chemical shifts and changes of signal sequences are observed relative to Battersby's study of cobester solutions in C₆D₆.