cobyrinic acid

Corrin with 8 methyl groups at positions 1, 2, 5, 7, 12 (2), 15, and 17; —CH₂COOH groups at positions 2, 7, and 18; —CH₂CH₂COOH groups at positions 3, 8, 13, and 17; and divalent cobalt centered among the four nitrogens. The acid side chains are designated, in numeric order, a, b, c, d, e, f, and g. It is a part of the vitamin B₁₂ structure.