Regioselective modification of methyl acrylate telomers by enzyme catalysis. Part 2. Influence of the telogen segment on the selectivity

Abstract

It has been shown in Part 1 that the transesterification of methyl acrylate telomers by lipase catalysis in toluene at 50°C is a regioselective modification. Indeed, only the ester functions of the end-groups (A and C functions) and those of the monomer units linked to the telogen segment (B function) were modified. The reactivity of the latter was not expected according to data on the specificity of the Rhizomucor miehei lipase, so that has questioned the influence of the telogen structure on the recognition of the B methyl ester by the enzyme. In this article, methyl acrylate telomers were synthesized from new telogens and their modification by lipase catalysis was investigated under the same conditions as in Part 1. The main result is that the B function is still reactive whatever the structure of the incorporated telogen. Further investigations should be done in order to understand the peculiar contribution of the sulphur atom to the regioselective modification of the telomers. A detailed structural analysis of the telomers was performed by proton NMR spectroscopy and size exclusion chromatography. It supports the very precise action of the enzymatic catalyst. Lipase catalysis in this field opens up many potential applications of new designed acrylate oligomers.