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13 C NMR studies of the friedelane series of triterpenoids and the conformation of the D and E rings in friedelan‐7‐one
Author(s) -
Prakash Om,
Roy Raja,
Garg H. S.,
Bhakuni D. S.
Publication year - 1987
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.1260250110
Subject(s) - chemistry , heteronuclear molecule , stereochemistry , dept , diol , two dimensional nuclear magnetic resonance spectroscopy , triterpenoid , nuclear magnetic resonance spectroscopy , chemical shift , nmr spectra database , spectral line , organic chemistry , physics , astronomy
The 13 C chemical shifts in the spectra of friedelan‐7‐one (1), methyl 3‐oxofriedelan‐25‐oate (2), methyl friedelan‐25‐oate (3), 7‐oxofriedelan‐3‐α‐yl acetate (4), friedelan‐3‐one (5), 2‐hydroxy‐3, 4‐ seco ‐friedelan‐3‐oic acid (6), methyl 2‐oxo‐3,4‐ seco ‐friedelan‐3‐oate (7), methyl 2‐hydroxy‐3,4‐ seco ‐friedelan‐3‐oate (8) and 3,4‐ seco ‐friedelan‐2,3‐diol (9) have been fully assigned using two‐dimensional heteronuclear correlation NMR spectroscopy, BB proton decoupled, DEPT and selective heteronuclear spin decoupling methods. These assignments and the observation of substantial NOEs between 26‐methyl and 28‐methyl and between 28‐methyl and 30‐methyl support the boat to boat conformations for the D and E rings in 1. Corrections and correlations are made of some earlier literature assignments of friedelanones.