Enzymatic Polymerization of Poly(ε-CL) Containing an Ethyl Glucopyranoside Head Group: An NMR Study

Abstract

The usefulness of the 2D-NMR techniques in the structure determination of the oligo ε-caprolactone ethyl glucopyranoside (oilgo(ε-CL) EGP) conjugate, synthesized by a lipase-catalyzed regioselective reaction, is described. Data from a ¹³C–¹³C COSY NMR spectrum of the ethyl glucopyranoside is used for complete and unambiguous assignments of the carbon resonances in the ¹³C NMR spectrum of the anomeric mixture of EGP. A comparison of the DEPT-135 spectrum of the product oilgo(ε-CL) EGP conjugate with that of the starting material, ethyl glucopyranoside (EGP), led to the conclusion that the lipase-catalyzed ring-opening of ε-CL initiated by a multifunctional initiator, EGP, proceeded in a regioselective fashion. Also, a detailed analysis of the NMR data has allowed determination of the site for lipase-catalyzed ring-opening polymerization of ε-CL. Our study suggests that among the possible four initiation sites in EGP only the hydroxyl group on carbon C-6 took part in the initiation process.

Keywords

Lipase Ethyl glucopyranoside ε-Caprolactone Ring-opening polymerization Two-dimensional NMR Regioselectivity Multifunctional initiator Site of reaction Caprolactone Glucopyranoside

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