Dipyrrinones-Constituents of the Pigments of Life. A Review

Boiadjiev, Stefan E.; Lightner, David A.

doi:10.1080/00304940609355999

Cited by 22 publications

(8 citation statements)

References 255 publications

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“…The syntheses of 1 and 2 thus followed a straightforward pattern (Scheme 2) whereby the end ring pyrrolinone precursor, 5-(bromomethylene)-4-ethyl-3-methyl-2-oxo-2,5-dihydropyrrole [24], was condensed [16, 17, 24, 25] by HBr catalysis in hot CH 3 OH with a suitable 1,2-dipyrrylethane ( 13 and 14 ). Initially, we thought that condensation using ethenes 11 or 12 might suffice, but that proved obstinate and unworkable; whereas, the reduced 13 and 14 reacted satisfactorily.…”

Section: Resultsmentioning

confidence: 99%

Homorubins and homoverdins

Pfeiffer¹,

Dey

Falk

et al. 2014

Monatsh Chem

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The syntheses are described for centrally expanded bilirubin analogs: b-homorubins with propionic and butyric acid groups in the positions corresponding to the propionic acids of bilirubin. Their syntheses were accomplished by coupling two equivalents of a reactive monopyrrole (5-(bromomethylene)pyrrolin-2-one) to a dipyrrylethane. The corresponding b-homoverdins and dehydro-b-homoverdins were prepared by dehydrogenating the rubins or their dimethyl esters using DDQ. As supported by NMR measurements and molecular mechanics calculations, the homorubins are found to engage in conformation-determining intramolecular hydrogen bonding between the dipyrrinone and carboxylic acid moieties. Likewise, the homoverdins are believed to favor intramolecularly hydrogen-bonded conformations.

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Section: Resultsmentioning

confidence: 99%

Homorubins and homoverdins

Pfeiffer¹,

Dey

Falk

et al. 2014

Monatsh Chem

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“…This is consistent with earlier studies showing that dipyrrinones are avid hydrogen bonders that bind strongly to one another as intermolecularly hydrogen‐bonded dimers, except when a carboxylic acid is attached to an appropriate site on the dipyrrinone backbone. In that event, the dipyrrinone preferentially hydrogen bonds either intramolecularly to the carboxylic acid and is monomeric or forms a stack dimer . Consistent with those observations unless self‐aggregation is promoted, bilirubins are typically monomeric, but analogs lacking carboxylic acid groups, eg, dimethyl esters and those with alkyl groups in place of CO 2 H are dimeric .…”

Section: Introductionmentioning

confidence: 52%

On the aggregation of bilirubinoids in solution as evidenced by VCD and ECD spectroscopy and DFT calculations

et al. 2017

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Vibrational and electronic circular dichroism (VCD and ECD) spectra of 3 optically active bilirubin analogs with propionic acid groups replaced by (1) 1-(S)-methylpropyl groups, (2) 3-acetoxy-1-(S)-methylpropyl groups, and (3) 1-(S)-2-(R)-dimethyl-2-(methoxycarbonyl)ethyl groups have been recorded at different concentrations in chloroform. The aliphatic chains attached to C-8 and C-12 of the 3 chosen mesobilirubins were modified so as to possess no OH group. The variation of the VCD spectra with concentration is consistent with the formation of dimers at high concentration. Density functional theory and time-dependent density functional theory calculations on monomeric and dimeric forms support such a conclusion. Comparing with previous VCD (ECD) and IR (UV) studies of other mesobilirubin molecules, it is concluded that here, the key feature for aggregation is the missing OH groups on the propionic acid chains. The latter, in synergy with the polar groups of lactam moieties, appear to be involved in intramolecular phenomena and thus favor monomeric forms. Investigation of ECD and UV spectra of the same compounds in mixed DMSO/chloroform solutions provide further clues to the proposed picture.

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“…In contrast, the reactions between pyrrole and ortho esters under acidic conditions give rise to tris(pyrrol-2-yl)alkanes [335,336]. Moreover, condensation reactions between suitable pyrrole fragments and pyrrole-2-carboxaldehyde derivatives constitute a common strategy to numerous dipyrrins and dipyrrinones [337]. Under carefully controlled conditions, the reaction of pyrrole with formaldehyde may give bis(pyrrol-2-yl)methane (dipyrromethane) (222), which is a useful precursor for the synthesis of 5,15-disubstituted porphyrins, for example 223 (Scheme 4.59) [335].…”

Section: Nitrationmentioning

confidence: 92%