Stereoelectronic control of the tertiary ketol rearrangement: implications for the mechanism of the reaction catalysed by the enzymes of branched-chain amino acid metabolism, reductoisomerase and acetolactate decarboxylase
The alkali-catalysed rearrangement of (R)-[1-13C]-3-hydroxy-3-methylpentan-2-one has been studied. Rearrangement via a transition state having an anti arrangement of C–O bonds was preferred over that with a syn arrangement by a factor of 1.8:1. The result is of interest in relation to the mechanism of action of the enzymes reductoisomerase and acetolactate decarboxylase, both of which are involved in the metabolism of the branched-chain amino acids. The structure and relative configuration of the product 23 of bromolactonisation of N-methacrylolyl L-proline 22 were determined by X-ray crystallographic analysis.