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High‐field 1 H and 13 C NMR spectra of synthetic protostane derivatives: Total assignment by 2D NMR
Author(s) -
Paryzek Zdzislaw,
Martynow Jacek,
Shimo Tetsuro
Publication year - 1992
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260300703
Subject(s) - chemistry , chemical shift , carbon 13 nmr satellite , dept , carbon 13 nmr , nmr spectra database , nuclear magnetic resonance spectroscopy , lanostane , stereochemistry , lanthanide , spectral line , nuclear overhauser effect , two dimensional nuclear magnetic resonance spectroscopy , substituent , crystallography , fluorine 19 nmr , triterpene , organic chemistry , ion , medicine , physics , alternative medicine , pathology , astronomy
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.