Eine nicht-enzymatische Modellreaktion für die coenzym-B12-katalysierte Umlagerung von Methylmalonyl-CoA in Succinyl-CoA

Abstract

Für Reaktionen, die durch Vitamin B12 katalysiert werden, gibt es bis heute keinen chemisch plausiblen Mechanismus, was vor allem durch den Mangel an Modellreaktionen bedingt ist. Die photochemische Zersetzung des Cobalt‐Komplexes (1) könnte eine Modellreaktion für die vom Vitamin B12 katalysierte Umlagerung von Methylmalonyl‐CoA in Succinyl‐CoA sein. .

Investigation of the Mechanism of the Methylmalonyl-CoA Mutase Reaction with the Substrate Analogue: Ethylmalonyl-CoA

“…A methylene radical intermediate, however, would not only be compatible with the loss of identity of the 5'-hydrogen atoms, but would also be reactive enough to abstract a hydrogen radical from a non-activated position of the substrate, which is the next postulated step in the mechanism (Fig. Model experiments from our laboratory [50,51] 450 Mechanisni of the Methylmalonyl-CoA Mutase Reaction suggest a crucial role o f the cobalt atom in the rearrangement which does not necessarily mean that 0 bonds between substrate and cobalt must be formed as postulated by some authors [52]. This hydrogen transfer is further in agreement with the observed exchange of the migrating hydrogen with the 5'-hydrogen atoms of the coenzyme [46 -491.…”

Synthesis and Structure Determination of an Intramolecularly Alkylated Bridged Cobaloxime

“…Compound (2) was extended by two C atoms uia the mesylate (3) in a malonic ester synthesis to form 7-nonyn-1-01 (4), the mesylate of which (5) could be used for double alkylation of dimethyl malonate. Upon hydrolysis, decarboxylation, and reduction, the bisalkylated malonic ester (6) afforded 2-(7-nonynyl)-9-undecyn-I -01 (7), which was converted via the mesylate (8) into the bromomethyl derivative (9).…”