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Dependence of 1 H NMR chemical shifts of geminal protons of glycosyloxy methylene (H 2 ‐26) on the orientation of the 27‐methyl group of furostane‐type steroidal saponins

2004; Wiley; Volume: 42; Issue: 11 Linguagem: Inglês

10.1002/mrc.1474

1097-458X

Pawan K. Agrawal,

Natural product bioactivities and synthesis

An approach based on the difference (Delta(ab) = delta(a) - delta(b)) between the 1H NMR chemical shifts (delta(a), delta(b)) of the geminal protons of glycosyloxy methylene (H2-26) (Delta(ab) = <0.48 for 25R; Delta(ab) = >0.57 for 25S) is proposed for ascertaining 25R/25S orientation of the 27-methyl group of furostane-type steroidal saponins. These studies suggested the 25R-orientation of the 27-Me group for the furostanol glycosides isolated by Wu et al. from Tribulus terrestris.