The molecule is the intermediate in the biosynthesis of vitamin B12 from uroporphyrinogen III in which three methyl groups have been introduced at positions 2, 7 and 20 of the tetrapyrrole framework and in which the carboxymethyl group at position 2 has been oxidised to form a lactone ring. It is a conjugate acid of a precorrin-3B(7-) and a precorrin-3B(6-).
3-[(1R,2S,12Z,14S,15S,16Z,19S,20S)-5,9,19-tris(2-carboxyethyl)-4,10,15-tris(carboxymethyl)-2-hydroxy-2,15,20-trimethyl-22-oxo-23-oxa-24,25,26,27-tetrazahexacyclo[16.5.1.13,6.18,11.113,16.01,20]heptacosa-3,5,8,10,12,16,18(24)-heptaen-14-yl]propanoic acid