Selected Vitamins - Natural Products Chemistry: Sources, Separations, and Structures - page 137

1 H NMR

4

3

6

1 7

8

5

2!

FIGURE 12.11 1 H NMR spectrum of vitamin B 6 . (R. B. Rucker, J. Zempleni, J. Suttie, and
D. McCormick, eds., 2007, Handbook of Vitamins , 4th ed., Taylor & Francis.)

FIGURE 12.12 13 C NMR spectrum of vitamin B 6 . (J. L. Svirbely and A. Szent-Gyorgyi,
1932, Biochem J 26(3):865-870.)

12.7 VITAMIN B 12
The Vit B 12 (cobalamin) chemical structure is shown in Figure 12.13. It is a fascinat-
ing molecule, challenging the ingenuity of the natural products chemist. Over many
years of research this elegant structure has generated significant research studies
on the chemistry of pyrroles, porphyrins, and corrins, and their respective biosyn-
thetic pathways.
One of the unusual features of the molecule is the carbon-metal bond. Vit B 12 is
composed of a cobalt atom and a corrin ring, consisting of four pyrrole rings, which
gives a porphyrin-like structure. The rings contribute to four coordinates, the fifth