A C-H...O=C hydrogen bond? Intramolecular hydrogen bonding in a novel semirubin.

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 CDCl(3) 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 CHCl(3), but its methyl ester (2) tends toward being dimeric, like that of methyl xanthobilirubinate, which is dimeric.

• Authors: M T Huggins, D A Lightner
• Journal: The Journal of organic chemistry (J Org Chem) Vol. 66 Issue 25 Pg. 8402-10 (Dec 14 2001) ISSN: 0022-3263 [Print] United States
• PMID: 11735518 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Caproates
• Pyrroles
• Solvents
• semirubin
• hexanoic acid
• Chloroform
• Bilirubin

Topics

• Bilirubin (chemistry)
• Caproates (chemistry)
• Chloroform
• Hydrogen Bonding
• Magnetic Resonance Spectroscopy
• Models, Molecular
• Molecular Conformation
• Pyrroles (chemistry)
• Solvents
• Spectrophotometry, Infrared
• Spectrophotometry, Ultraviolet
• Volatilization