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Crystal Structure of Garciniaphenone and Evidences on the Relationship between Keto–Enol Tautomerism and Configuration
Author(s) -
Martins Felipe T.,
Camps I.,
Doriguetto Antônio C.,
dos Santos Marcelo H.,
Ellena Javier,
Barbosa Luiz C. A.
Publication year - 2008
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200890143
Subject(s) - chemistry , tautomer , enol , substituent , intermolecular force , moiety , delocalized electron , stereochemistry , keto–enol tautomerism , crystal structure , ring (chemistry) , crystal (programming language) , computational chemistry , crystallography , molecule , organic chemistry , computer science , programming language , catalysis
Garciniaphenone (= rel‐ (1 R ,5 R ,7 R )‐3‐benzoyl‐4‐hydroxy‐8,8‐dimethyl‐1,7‐bis(3‐methylbut‐2‐en‐1‐yl)bicyclo[3.3.1]non‐3‐ene‐2,9‐dione; 1 ), a novel natural product, was isolated from a hexane extract of Garcinia brasiliensis fruits. The crystal structure of 1 as well as the selected geometrical and configurational features were compared with those of known related polyprenylated benzophenones. Garciniaphenone is the first representative of polyprenylated benzophenones without a prenyl substituent at C(5). Notably, the absence of a 5‐prenyl substituent has an impact on the molecular geometry. The tautomeric form of 1 in the solid state was readily established by a residual‐electronic‐density map generated by means of a difference Fourier analysis, and there is an entirely delocalized six‐membered chelate ring encompassing the keto–enol moiety. The configuration at C(7) was used to rationalize the nature of the keto–enol tautomeric form within 1 . The intermolecular array in the network is maintained by nonclassical intermolecular H‐bonds.