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13 C NMR spectroscopy of aristolochic acids and aristololactams
Author(s) -
Priestap Horacio A.
Publication year - 1989
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.1260270508
Subject(s) - phenanthrenes , chemistry , phenanthrene , substituent , chemical shift , steric effects , nuclear magnetic resonance spectroscopy , organic chemistry , carbon 13 nmr , ring (chemistry) , stereochemistry , medicinal chemistry
The 13 C NMR spectra of more than 30 phenanthrene derivatives were recorded and their carbon shifts assigned. The compounds consisted of representative aristolochic acids and aristololactams, the phenanthrene alkaloid argen‐tinine and some derivatives. Assignments of the carbon resonances were carried out from chemical shifts, one‐bond and long‐range carbon‐hydrogen couplings and selective comparison of the phenanthrene derivatives with each other and with model compounds. The chemical shifts of the aromatic carbons were correlated with substituent effects. It was found that the shift changes on introduction of oxy functions in phenanthrenes parallel those reported for monosubstituted naphthalenes. Steric compression shifts observed in 3,4‐disubstituted and ring A polysubstituted phenanthrenes are discussed. Further evidence about the structures of the aristololactams CII, CIII, DII, DIII, enterocarpam‐I and enterocarpam‐II is provided, based on 13 C NMR data. The substituent parameters found for phenanthrene derivatives proved to be additive and their use in signal assignments is described.