Synthesis of Vitamin‐B₁₂ Derivatives with an Electropolymerizable Side Chain

Abstract

Three new derivatives of vitamin B,, with a pyrrole head group attached to the corrin ring have been prepared. Ligdnd-exchange reactions and reduction provided reactive Co"' and Co" complexes. Their electrochemical properties and their potential for fixation at the surface of electrodes by electropolymerization were studied.Introduction. -Model systems for enzyme-catalysed transformations play an important role for understanding the mechanism of such reactions. This is particularly important for reactions where cofactors are involved and become a conditio sine qua non for the coenzyme-B12-dependent transformations [I]. Detailed investigations in several laboratories have unravelled important features of the vitamin-BIZ-dependent reactions [ 2 ] , and many attempts have been undertaken to incorporate these results into model systems. Although many structural features have been reproduced in this way, further attempts are necessary for a more comprehensive modelling of the in vivo reactions. For example, the enantioselectivity in the methylmalonyl-succinyl rearrangement is rather low and the enantiomeric excesses (ee) of the product do not exceed 20% in reactions of racemic methylmalonyl substrates [3]. Our experiments with a homochiral methylmalonyl substrate has recently led to similar observations [4] '). Other aspects like stereospecific recognition of substrates by an appropriately modified vitamin-B catalyst deserve further attention. Whereas the mechanistic features of the in vivo methylmalonyl-succinyl rearrangement and similar rearrangements are emerging [ 6 ] , corresponding investigations in model systems have hitherto remained inconclusive [4].Our model systems, which incorporate features of molecular recognition between substrates and vitamin-B,,-derived catalysts both endowed with anchoring groups in the periphery, are driven by an electrochemical-photolytic cycle and lead to an enhanced rearrangement [7]. For further investigation of chiral recognition, transfer of chirality in the methylmalonyl-succinyl rearrangement, and other vitamin-B, ,-dependent reactions, and for a detailed investigation of the electronic features of these transformations, it is

Selectively Modified Cobyrinic Acid Derivatives

“…Therefore, a new approach was envisaged starting from c-acid 15. [14] First, acid 15 was coupled with propargylamine to give monoamide 16 in 90 % yield, which then underwent aminolysis with ethanolamine in the presence of benzotriazole/DBU to give selectively functionalized heptaamide 17 with no 8-OH group in 49 % yield (Scheme 3).…”

STM investigations of Au(111) electrodes coated with vitamin B12 derivatives

“…It has also been confirmed that vitamin B 12 , even if it is doped in a silica gel film, exhibits a high reactivity for dehalogenation of an organic halide [22]. More studies have been reported involving the electro-polymerization of vitamin B 12 derivatives with a pyrrole group in the side chain on glassy carbon substrates [23][24][25] and on polycrystalline Pt [26].…”

An innovative strategy for immobilization of receptor proteins on to an optical fiber by use of poly(pyrrole-biotin)

“…11-(1-Pyrrolyl) undecanol was prepared as described previously [34]. Pyrrole-biotin (Scheme 1) was synthesized by dissolving biotin (500 mg, 2 mmol), 11-(1-pyrrolyl)-undecanol (417 mg, 1.66 mmol), 3-dicyclohexylcarbodiimide (413 mg, 2 mmol), and 4-(dimethylamino) pyridine (81 mg, 0.66 mmol), together, in dry deoxygenated CH 2 Cl 2 (10 mL).…”