High-field 1H and 13C NMR spectra of synthetic protostane derivatives: Total assignment by 2D NMR

✍ Scribed by Zdzislaw Paryzek; Jacek Martynow; Tetsuro Shimo

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 621 KB
• Volume: 30
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260300703

✦ Synopsis

Abstract

Triterpenes with the protostane skeleton, which are available from biomimetic rearrangements of lanostane derivatives, were analysed by one‐ and two‐dimensional high‐field ^1^H and ^13^C NMR spectroscopy. Complete assignments of the proton and carbon signals of 11α‐acetoxy‐3β‐benzoyloxy‐5α.9β‐protost‐13(17)‐ene (4) and of 11α‐acetoxy‐31‐nor‐5α,9β‐protost‐13(17)‐en‐3‐one (5) are presented. The assignments were largely determined using substituent chemical shift and conformational effects and by a combination of DEPT, ^1^H‐‐^1^H COSY, ^1^H‐‐^13^C HETCOR and XCORFE spectra. Nuclear Overhauser effect and lanthanide‐induced shift experiments were also useful for assignments. The results confirm the structure of 4 proposed previously on the basis of the low‐resolution spectra, and provide evidence for the structure of the new fusidane 5. The effect of methyl substitution at the 4β‐position on the ^13^C chemical shifts is briefly discussed. The assignment of the sp^2^ carbon atom signals reported for diacholest‐13(17)‐enes is revised on the basis of the XCORFE experiments.