Preparation of Dicyano- and Methylcobinamide from Vitamin B_12a

Abstract

Treatment of vitamin B_12a 1 (hydroxycobalamin hydrochloride, aquocobalamin) with NaBH₄ and ZnCl₂ leads to the selective cleavage of the nucleotide loop and gives dicyanocobinamide 2a in good yield. Methylcobinamide 4 was prepared from 2 via aquocyanocobinamide 3. The glutathione-mediated methylation of 3 in a pH 3.5 buffer solution proceeded with MeI, but not with MeOTs.

Key words

vitamin - phosphorus ester - hydrolysis - alkylations - ligands

References

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11

This reaction was suggested by a referee for our paper in ref. 7.

12

We define ‘cobinamide’ as the corrinoid ring system without the axial ligands.

13

The results are based on the work of C. Wedemeyer-Exl, postdoctoral fellow 1998-1999; preliminary results were obtained in 1997 by M. Pfammatter, M. Buhmann M., and C. Nachtigal.