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Quantitative Determination of Resin Loading in Solid-Phase Organic Synthesis Using (13)C MAS NMR
1Swiss Federal Laboratories for Materials Testing and Research (EMPA), Überlandstr. 129, CH-8600 Dübendorf, Switzerland, Lipal Biochemicals, Winterthurerstr. 190, CH-8057 Zürich, Switzerland, and Polyphor Ltd., Gewerbestr. 14, CH-4123 Allschwil, Switzerland.
Journal of Combinatorial Chemistry
|January 10, 2001
Summary
Quantitative carbon nuclear magnetic resonance spectroscopy ((13)C NMR) offers a reliable method for determining resin loadings in solid-phase organic synthesis. This technique provides accurate results comparable to established methods without needing specific functional groups.
Area of Science:
- Analytical Chemistry
- Organic Chemistry
- Materials Science
Background:
- Solid-phase organic synthesis (SPOS) relies on accurate quantification of resin-bound compounds.
- Traditional methods for determining resin loading can be labor-intensive or require specific functional groups.
Purpose of the Study:
- To investigate the utility of quantitative carbon nuclear magnetic resonance spectroscopy ((13)C NMR) for determining resin loadings.
- To establish (13)C NMR as a viable alternative to existing analytical techniques for SPOS.
Main Methods:
- Acquisition of magic angle spinning (MAS) NMR spectra for solvent-swollen resins.
- Utilized tetrakis(trimethylsilyl)silane as an external reference or resin carbon resonances as an internal standard.
- Employed the two pulse phase modulation (TPPM) proton decoupling sequence on a 7 mm CP/MAS probe.
Main Results:
- Quantitative (13)C NMR successfully determined resin loadings for functionalized Wang and trityl resins.
- Results obtained via (13)C NMR were consistent with established analytical methods.
- The method is independent of the need for a quantifiable chromophore on the resin.
Conclusions:
- Quantitative (13)C NMR is a robust and accurate method for assessing resin loadings in SPOS.
- This technique offers a versatile analytical tool for various resins and functionalizations.
- The (13)C NMR approach simplifies loading determination, broadening its applicability in synthetic chemistry.