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

Volume 52, Number 11 (Nov. 1998) Page 1472-1478

Bisht, Kirpal S.; Gross, Richard A.; Cholli, Ashok L.

The usefulness of the 2D-NMR techniques in the structure determination of the oligo epsilon-caprolactone ethyl glucopyranoside (oilgo(epsilon-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 DEPT135 spectrum of the product oilgo(epsilon-CL) EGP conjugate with that of the starting material, ethyl glucopyranoside (EGP), led to the conclusion that the lipase-catalyzed ring-opening of epsilon-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 epsilon-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.