NMR assignment of the absolute configuration of C-25 in furostanol steroidal saponins
VL Challinor, S Piacente, JJ De Voss - Steroids, 2012 - Elsevier
The chemical shifts of the geminal proton resonances of H2-26 (δa and δb) are a widely
used predictor of C-25 stereochemistry in furostanol steroidal saponins, being in general
more resolved in 25S than 25R compounds. Unexpectedly, we found that application of this
empirical rule in different solvents led to conflicting assignments of stereochemistry. An
experimental survey revealed that, while the chemical shifts of H2-26 exhibit a dependence
on C-25 configuration, it is less pronounced in methanol-d4 than pyridine-d5 solvent, and …
used predictor of C-25 stereochemistry in furostanol steroidal saponins, being in general
more resolved in 25S than 25R compounds. Unexpectedly, we found that application of this
empirical rule in different solvents led to conflicting assignments of stereochemistry. An
experimental survey revealed that, while the chemical shifts of H2-26 exhibit a dependence
on C-25 configuration, it is less pronounced in methanol-d4 than pyridine-d5 solvent, and …
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