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13 C NMR spectroscopy of naphtho‐γ‐pyrones
Author(s) -
Priestap Horacio A.
Publication year - 1986
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.1260241006
Subject(s) - chemistry , ring (chemistry) , pyran , chemical shift , nuclear magnetic resonance spectroscopy , stereochemistry , deuterium , aryl , hydrogen , carbon 13 nmr , carbon fibers , spectroscopy , crystallography , organic chemistry , alkyl , physics , materials science , quantum mechanics , composite number , composite material
The 13 C NMR spectra of three naphtho‐γ‐pyrones produced by Aspergillus fonsecaeus (NRRL 67, 0 16–1), viz. 5‐hydroxy‐6,8‐dimethoxy‐2‐methyl‐4 H ‐naphtho[2,3‐ b ]pyran‐4‐one (rubrofusarin B), 2,3‐dihydro‐2,5‐dihydroxy‐6,8‐dimethoxy‐2‐mehtyl‐4 H ‐naphtho[2,3‐ b ]pyran‐4‐one (fonsecin B) and 2,3‐dihydro‐2,5,8‐trihydroxy‐6‐methoxy‐2methyl‐4 H ‐naptho[2,3‐ b ]pyran‐4‐one (fonsecin), have been determined. Assignments of the carbon resonances were carried out from chemical shifts, long‐range carbon‐hydrogen couplings and hydrogen–deuterium exchange information. Carbon shift assignments previously reported for fonsecin have been revised. The C‐4 and C‐5 signals show that the angle of twist of the carbonyl group with the aryl ring system is larger in fonsecin than in fonsecin B, indicating the occurrence of different preferred conformations in the dihydropyrone ring of these compounds.