PREPARATION AND STRUCTURE PROOF OF THE 4 ISOMERIC DICYANOCOBYRINIC ACID HEXAMETHYL ESTER MONOAMIDES CARRYING THE AMIDE GROUP ON A PROPIONIC-ACID SIDE-CHAIN

Selective ammonolysis of dicyano-cobalt(III)cobyrinic acid heptamethyl ester (cobester, 2) furnishes the four isomeric hexamethyl ester mono amides 2b, 2d, 2e, 2f carrying the amide function on one of the propio nic acid side chains. The isomers were separated by liquid-liquid chro matography and their structures determined by a comparison of their C- 13-NMR spectra with the spectrum of 2. Amide 2f served as the link bet ween synthetic and authentic vitamin B-12 derived material in the tota l synthesis of vitamin B-12.