Synthesis and unusual properties of expanded bilirubin analogs

Nogales, Daniel F.; Anstine, D. Timothy; Lightner, David A.

doi:10.1016/s0040-4020(01)85333-3

Cited by 23 publications

(14 citation statements)

References 24 publications

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“…And in this case, the situation appears to be analogous to that observed when dipyrrinones are linked by an ethyne (−C≡C−) unit, which also gives red-orange solutions, as was observed previously [33]. The dehydro- b -homoverdins [19, 20] exhibited the reddish color associated with the dipyrrylmethene chromophore [30, 34] and with α-benzylidene dipyrrinones [35, 36]. …”

Section: Resultssupporting

confidence: 70%

“…In connection with our interest in centrally expanded [11, 16, 33, 35, 50–52] and contracted [53] analogs of the synthetic model (mesobilirubin-XIIIα) for the natural pigment of human bile and jaundice [1], we prepared homorubin 1 and its analog 2 , with butyric acid groups replacing propionic acids. Yellow 1 and 2 preferentially adopt folded, intramolecularly hydrogen-bonded conformations and exhibit a lipophilicity comparable to that of mesobilirubin-XIIIα.…”

Section: Concluding Commentsmentioning

confidence: 99%

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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: Resultssupporting

confidence: 70%

Section: Concluding Commentsmentioning

confidence: 99%

Homorubins and homoverdins

Pfeiffer¹,

Dey

Falk

et al. 2014

Monatsh Chem

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“…Its proclivity to form intramolecular hydrogen bonds to a carboxylic acid group was explored in numerous linear tetrapyrroles [16–22], with chemically-designed dipyrrinones [10–13, 23–25] and even with a few centrally expanded bilirubin analogs (Fig. 1B) [26–30], some of which (Fig. 1C) were designed to produce a concave conformation of possible use in sequestering planar guests.…”

Section: Introductionmentioning

confidence: 99%

“…1B exhibited most of the usual properties of bilirubin, the pigments of Fig. 1C proved to be too insoluble in nonpolar solvents, e.g., CHCl 3 , for ascertaining conformation and complexation [30]. Subsequent to that study, it was learned that tripyrrole D-1 [31] and hemirubin D-2 [32, 33] of Fig.…”

Section: Introductionmentioning

confidence: 99%

Intramolecular hydrogen bonding and linear pentapyrrole conformation

Anstine

Lightner

2014

Monatsh Chem

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Three new linear pentapyrrole rubinoid analogs: 2,3,7,8,17,18,22,23-octamethyl-12,13-bis-(2-carboxyethyl)-1,10,15,24,25,27,28,29-octahydro-27H-pentapyrrin-1,24-dione and 2,3,8,12,13,17,22,23-octamethyl-7,18-bis-(2-carboxyethyl)-1,10,15,24,25,26,27,28,29-octahydro-27H-pentapyrrin-1,24-dione, and its 7,18-dihexanoic acid analog were synthesized, respectively, from 2,3,7,8-tetramethyl-(10H)-dipyrrin-2-one, from 2,3,8-trimethyl-7-[2-(methoxycarbonyl)ethyl]-(10H)-dipyrrinone, and 2,3,8-trimethyl-7-[5-(methoxycarbonyl)pentyl]-(10H)-dipyrrinone. 13C NMR and 1H NMR measurements in (CD3)2SO confirmed the pentapyrrole structures, while 1H NMR data indicate intramolecular hydrogen bonding between the CO2H and dipyrrinone groups. Molecular mechanics modeling studies suggest stable U-shape conformations capable of encapsulating small planar aromatic molecules.

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“…[11][12][13][14][15][16] In contrast, metal complexes bearing acyclic polypyrroles constructed of more than five pyrroles are still rare because of the limited availability of synthetic routes to prepare them. [17][18][19][20][21][22] As an exceptional example, a new dicopper(II) complex bearing acyclic heptapyrrolic helices has been prepared from dicopper(II) heptaphyrin by reaction with O 2 . [7] In this reaction, O 2 was not activated at the metal center but reacted with the heptaphyrin ligand directly.…”

mentioning

confidence: 99%

Conversion of Cobalt(II) Porphyrin into a Helical Cobalt(III) Complex of Acyclic Pentapyrrole

et al. 2011

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Conversion of artificial porphyrin to acyclic polypyrrole by oxidation is important not only for model reactions of heme oxygenase (HO), which converts heme to biliverdin, [1][2][3] but also for the syntheses of new acyclic polypyrroles. [4][5][6][7][8][9][10] Biliverdin-type ligands are nonplanar tetrapyrrole derivatives and have been utilized for the syntheses of metal complexes with helical structures that are easily racemized, owing to its low steric hindrance for interconversion. [11][12][13][14][15][16] In contrast, metal complexes bearing acyclic polypyrroles constructed of more than five pyrroles are still rare because of the limited availability of synthetic routes to prepare them. [17][18][19][20][21][22] As an exceptional example, a new dicopper(II) complex bearing acyclic heptapyrrolic helices has been prepared from dicopper(II) heptaphyrin by reaction with O 2 . [7] In this reaction, O 2 was not activated at the metal center but reacted with the heptaphyrin ligand directly.Two intrinsic effects of the coordination environment around heme on the activation of the O 2 molecule have been proposed in the biological system. One is the electron donation from coordinating bases such as imidazole and thiolate at the fifth coordination site to the iron center, and the other is the hydrogen bond from the histidine residue to the O 2 molecule bound at the metal center. When these two effects contribute cooperatively, this activation mechanism is called a "push-pull" mechanism. [3,23] To mimic the pull effects, some porphyrin ligands bearing carboxylic acid, which could form a hydrogen bond to the bound O 2 , have been designed and synthesized. [4,[23][24][25] For example, Chang and co-workers have shown that Co II porphyrin complex bearing naphthoic acid, [Co(npca-por)], converted to metal-free biliverdin-type acyclic polypyrrole by reaction with O 2 . This reaction proceeds under ambient condition without coordination of any bases at the axial site.[4] The authors proposed that in this system, the carboxylic acid group protonated the coordinating O 2 molecule to yield a Co III À OOH species as an intermediate. Although this system mimicked the pull effect well, porphyrin complexes which require both push and pull effects for the cleavage of the porphyrin ring are still not known.Recently, we designed a new porphyrin ligand (amtpp; Scheme 1) that has an amide group in the ortho position of a phenyl ring of tetraphenylporphyrin (H 2 tpp) to mimic the pull effect by histidine residue in the biological system. We found that the imidazole adduct [Co(amtpp)(1-MeIm)] (1-MeIm = 1-methylimidazole) activated O 2 , thus converting to a new Co III helical complex with a coiled acyclic pentapyrrole-type ligand, despite the fact that the Co II complex [Co(amtpp)] (1) was inert to air (Scheme 1). Moreover, we have found that chiral axial ligands (S)-nicotine and (S)-cotinine induced the (M)-helical form preferentially in this conversion system. Herein, we report the synthesis and structure of the Co-amtpp complex and the uni...

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Synthesis and unusual properties of expanded bilirubin analogs

Cited by 23 publications

References 24 publications

Homorubins and homoverdins

Homorubins and homoverdins

Intramolecular hydrogen bonding and linear pentapyrrole conformation

Conversion of Cobalt(II) Porphyrin into a Helical Cobalt(III) Complex of Acyclic Pentapyrrole

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