Abstract
(4Z)-8-(5-Carboxypentyl)-9-butyl-2,3-diethyl-dipyrrin-1-one (1), a new analogue of xanthobilirubic acid, (4Z)-8-(carboxyethyl)-2,7,9-dimethyl-3-ethyl-dipyrrin-1-one, was synthesized in four steps from the known 2,3-diethyl-dipyrrin-1-one. Whereas xanthobilirubic acid (which is a model for one-half of bilirubin, the yellow pigment of jaundice) and its homologues with hexanoic and longer acid chains at C-8 engage only in intermolecular hydrogen bonding, 1 is found to engage in intramolecular hydrogen bonding. In CDCl3 solution, dipyrrinone 1 adopts an anti-Z conformation, and its hexanoic acid COOH is hydrogen-bonded to the lactam H-N-C=O and to the pyrrole C(7)-H but not to the pyrrole NH. The latter constitutes an example of a hydrogen bond of the type C-H···O=C, weak and detected typically in crystals. Dipyrrinone 1 is found by vapor pressure osmometry to be monomeric in CHCl3, but its methyl ester (2) tends toward being dimeric, like that of methyl xanthobilirubinate, which is dimeric.
Original language | English |
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Pages (from-to) | 8402-8410 |
Number of pages | 9 |
Journal | Journal of Organic Chemistry |
Volume | 66 |
Issue number | 25 |
DOIs | |
State | Published - Dec 14 2001 |
Externally published | Yes |
Scopus Subject Areas
- Organic Chemistry