~1H,~13C-HSQC HR-MAS NMR as a Tool for Investigating the Quality of Fmoc-AA-Wang Resins for SPPS

摘要

The use of high quality starting materials in SPPS is a prerequisite to obtain peptides of high purity and with high yields [1]. Beside AA derivatives and reagents, the quality of employed resins like Fmoc-AA-Wang is also of crucial importance. Due to the insolubility of resins, the range of analytical methods suitable to assess their quality directly is restricted. Many attempts have been described in literature to overcome this difficulty [2-4]. Nevertheless, the quality control of resin beads still remains challenging compared to building blocks and reagents. MAS NMR enables direct analysis of resin beads without prior cleavage and sample preparations. 1D ~13C MAS NMR with conventional MAS probes has already been used successfully to determine quantitatively the loading of resins using internal references [5]. The significantly better resolution of HR-MAS probes enabled quantitative results from 1D ~1H MAS NMR spectra as well [6,7]. Owing to overlap of resonances, the 1D NMR methods cannot always be successfully applied, particularly in cases with weak resonances. Herein, results obtained with the much more powerful HSQC tool on the generic example Fmoc-Ala-Wang resin arc presented.