Application of gel-phase 13c-nmr to monitor solid phase peptide synthesis

The results presented in this article show the general applicability of gel-phase ¹³C-NMR to monitor solid phase peptide synthesis on the most commonly used polystyrene-based resins. The optimal conditions to acquire gel-phase ¹³C-NMR spectra of copoly(styrene-l%-divinylbenzene) has been determined. The technique proved to be applicable to characterize polystyrene-based starting supports as well as to the determination of their degree of functionality and purity. The stage-by-stage ¹³C-NMR characterization of the growing peptide chain during the synthesis of tripeptide H-Asn-(N-Me)Ala-Thr-NH₂ on a benzhydrylamine resin is described. The structural information, derived from this technique is relevant for the synthetic process as the spectra can be acquired under similar conditions. The characteristics of the spectra facilitate monitoring of coupling and deprotection reactions.