C-13 NMR RELAXATION-TIMES OF A TRIPEPTIDE METHYL-ESTER AND ITS POLYMER-BOUND ANALOGS

Carbon-13 spin-lattice relaxation times of the tripeptide methyl ester Boc-Gly-Pro-Pro- OMe and its polymer-bound analogues are reported. Line widths of the signals of α-carbon atoms of Pro(2) and Pro(3) are also measured and an interpretation of the line broadening is presented. As polymeric macromolecules the following supports were employed: insoluble cross-linked polystyrene (PS), soluble poly(oxyethylene) (POE), and the graft copolymer poly(oxyethylene)-polystyrene-divinylbenzene (POE- PS). The molecular motions of the peptide moieties were determined by analysis of the relaxation time T1. The peptide methyl ester was synthesized classically and after saponification of the ester group it was coupled to the polymers according to known procedures. In the present studies for the measurements of the Tl values only the signals of the trans forms of the X-Pro sequence have been considered. The investigations revealed that the T1 values and hence the mobility of the C atoms of the peptide esters decrease in the sequence methyl ester > POE ester ≥ POE-PS ester > PS ester. © 1990, American Chemical Society. All rights reserved.