Truncated vitamin B12 derivative with the phosphate group retained

Cobyric acid and cobinamide are valuable building blocks for the synthesis of artificial cobalamins modified at the nucleotide loop. However, truncated vitamin B[Formula: see text] derivatives are devoid of the phosphate group. We have found that 2-iodoxy benzoic acid-mediated phosphorolysis leads to the cleavage of only one of the phosphodiester bond giving a vitamin B[Formula: see text] analogue with the phosphate moiety preserved. Subsequent alkylation with an organic halide establishes its role as a precursor for the synthesis of vitamin B[Formula: see text] mimics modified at the nucleotide loop.

Total synthesis of vitamin B12 — a fellowship of the ring

In the synthesis of cobyric acid following an arduous 60-step synthesis of the tetrapyrrole corrigenolide, Woodward demonstrated that ring cyclization yielded unexpectedly the corrin cyclic ether (Fig. 2). Its structure was chosen as the chemistry logo for the 1970 IUPAC meeting. It was a reminder that chemistry can be capricious and beautiful. This article is a tribute to the 50-year career in porphyrins of Professor Kevin M. Smith and describes his early contributions with colleagues in the synthetic quest of a related porphyrin molecule, vitamin B12 (Fig. 1a).