13C Cross-Polarization MAS NMR Study of Some Steroidal Sapogenins

✍ Scribed by Iwona Wawer; Andrzej A. Cichowlas; Jadwiga Nartowska

• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 110 KB
• Volume: 20
• Category: Article
• ISSN: 0926-2040
• DOI: 10.1006/snmr.2001.0028

✦ Synopsis

Cross-polarization (CP) magic angle spinning (MAS) solid-state 13 C NMR spectra of five steroidal sapogenins: tigogenin ((25R)-5α-spirostan-3β-ol), hecogenin (3β-hydroxy-(25R)-5α-spirostan-12-one), diosgenin (( 5 -(25R)-5α-spirosten-3β-ol), sarsasapogenin ((25S)-55βspirostan-3β-ol), and smilagenin ((25R)-5β-spirostan-3β-ol) were recorded. The solid-state chemical shifts are almost the same as for solution, which indicate that confirmations of sapogenins are similar in both phases. The doubling of some resonances in the spectra of solid diosgenin shows that there are two molecules in the crystallographic asymmetric unit. The cross-polarization time constants T CP and relaxation times in the rotating frame T H 1ρ were obtained from the variable-contact cross-polarization experiments for tigogenin and diosgenin. The values of T CH for methyl carbons indicate fast rotation of methyl groups and are close (0.30-0.35 ms), suggesting that the interaction with their intramolecular neighbors is similar. The values of T H 1ρ for carbons of tigogenin are longer than of diosgenin. Very efficient crosspolarization dynamics results in short time required for obtaining a spectrum of sapogenin of remarkably good quality.