Cyanocobalamin has been modified to afford a strapped hydrophobic vitamin B12 by introducing a 1,3-phenylenediacetyl moiety into the peripheral site of the corrin's B ring. The modified complex was characterized by various spectroscopic methods and cyclic voltammetry in comparison with the corresponding data for a simple hydrophobic vitamin B12 without a strapping moiety. The alkylation of hydrophobic vitamin B12 derivatives with racemic 3-bromo-2-methylpropionic esters at the β-axial site was carried out in methanol, and extents of the enantioselectivity were examined by 1H NMR spectroscopy. The strapped hydrophobic vitamin B12 and a simple hydrophobic vitamin B12 were found to react with (S)-3-bromo-2-methylpropionates more readily than the corresponding R-enantiomers; the highest S-selectivity (75% ee) was observed with the strapped hydrophobic vitamin B12. The 5-enantioselectivity was discussed from a stereochemical viewpoint based on the conformational search for the alkylated hydrophobic vitamin B12 by means of molecular mechanics and dynamics calculations.
|Number of pages||9|
|Journal||Journal of the Chemical Society, Perkin Transactions 2|
|Publication status||Published - 1995|
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