High-resolution magic angle spinning HR-MAS NMR

High-resolution magic-angle spinning (HR-MAS) NMR permits analysis of products still attached to solid-phase resin beads. This makes quantitation... 

High-resolution magic-angle-spinning (HR MAS) solid state NMR was shown to provide compound identification of separated TLC zones without elution (Wilson et al., 1997). Zones were removed by scraping from Cij-bonded plates, slurried with D2O, and placed in a sealed 4-mm zirconia MAS rotor of a Brucker DRX-600 NMR spectrometer for H NMR observation. Spectra were illustrated for 10 J.g of salicylic acid and phenolphthalein glucuronide, which quantity can be obtained from spots on an analytical plate without the need for preparative layer chromatography. 

Figure 3.5. (A) JH NMR spectrum of the Brooksville fulvic acid (BFA) dissolved in d6-DMSO and (B) HR-MAS NMR spectrum of the BFA-clay complex swollen in g 6-DMSO. Inset shows that lower abundance aromatic species are present in the spectrum in part B. Reprinted from Simpson, A. I, Simpson, M. I, Kingery, W. L., Lefebvre, B. A., Moser, A., Williams, A. I, Kvasha, M., and Kelleher, B. R (2006). The application of 1H high-resolution magic-angle spinning NMR for the study of clay-organic associations in natural and synthetic complexes. Langmuir 22,4498 1503, with permission from the American Chemical Society.

The effectiveness of the glycal assembly approach to solid support oligosaccharide synthesis was impressively documented by on-resin analysis. The crude product of the multistep synthesis of trisaccharide 32 (Scheme 16) was monitored by high-resolution magic angle spinning NMR (HR-MAS) [70]. 

While specific applications of gel-phase NMR have been useful for SPS reaction monitoring, the great potential of SPS NMR is in the determination of structure and the measurement of purity and yields, especially through the use of magic angle spinning-high-resolution (MAS-HR) NMR techniques. This important topic will be addressed in Section 1.4.6. 

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