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Syntheses of bile pigments. Part 15 . First unequivocal assignment of the absolute configuration of an urobilinoid bile pigment by X‐ray diffraction analysis of its synthetic precursor
Author(s) -
Pasquier Cécile,
Gossauer Albert,
Keller Walter,
Kratky Christoph
Publication year - 1987
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.19870700815
Subject(s) - chromophore , chemistry , absolute configuration , pigment , bile pigments , stereochemistry , helicity , diffraction , absorption (acoustics) , cotton effect , x ray , photochemistry , organic chemistry , circular dichroism , optics , physics , particle physics
(−)‐(4 S ,16 S )‐8, 12‐bis[de(2‐carboxyethyl)]mesourobilin‐IIIα hydrochloride ( 8 ) has been synthesized from the enantiomerically pure 1,4,5,10‐tetrahydro‐1‐oxodipyrrin‐9‐carboxylic‐acid precursor 6a whose absolute configuration was determined by X‐ray diffraction analysis of the N ‐[( S )‐1‐(1‐naphthyl)ethyl] carboxamide 7b . The present results prove unequivocally that an ( S , S )‐configurated urobilin chromophore displays a negative Cotton effect in the VIS absorption range. However, the helicity of the inherently dissymmetric chromophore remains undetermined.