Reduction-Labile Organo-cob(III)alamins via Cob(II)alamin: Efficient Synthesis and Solution and Crystal Structures of [(Methoxycarbonyl)methyl]cob(III)alamin
✍ Scribed by Michael Puchberger; Robert Konrat; Bernhard Kräutler; Ulrike Wagner; Christoph Kratky
- Book ID
- 102254236
- Publisher
- John Wiley and Sons
- Year
- 2003
- Tongue
- German
- Weight
- 179 KB
- Volume
- 86
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
Abstract
An efficient synthesis of Coβ‐[(methoxycarbonyl)methyl]cob(III)alamin (6) is reported as an example of a new method for the preparation of some easily reducible organo‐cob(III)alamins via the alkylation of cob(II)alamin. The procedure represents a considerable improvement compared to earlier methods that were based on an alkylation of cob(I)alamin. Thus, aquacob(III)alamin chloride (5^+^⋅Cl) was reduced to cob(II)alamin (4), either by controlled potential electrolytic reduction or with an excess of sodium formate as reducing agent. The solution of 4 was then treated with an excess of methyl bromoacetate while being reductively poised potentiostatically or kept reduced by the formate, to give crystalline 6 in a yield of up to 91%. The structure of 6 in aqueous solution was mainly established by the completely assigned ^1^H‐ and ^13^CNMR spectra (Table 1). The NOE data (Table 2) were best rationalized by the presence of a single main conformation of the (methoxycarbonyl)methyl ligand. Single crystals of 6 were obtained by crystallization from an aqueous solution, and the crystal structure was determined by X‐ray analysis at cryotemperatures. The NMR and crystallographic data of 6 indicated similar structures in aqueous solution and in the crystal with the (methoxycarbonyl)methyl ligand preferring a ‘southern' orientation in each case.