A theoretical and experimental NMR study of (+)-biotin methyl ester

The structure in solution and in the solid state of (+)-biotin methyl ester is discussed based on NMR chemical shifts measured in CDCl3 solution and in the solid state together with GIAO calculations at the B3LYP/6-311++G∗∗ theoretical level. In the solid state, only the extended conformation exists while in CDCl3 solution a small amount of a IMHB conformation is present in a fast dynamic equilibrium with the preceding one. The HB involves the CO oxygen atom of the ester.