- Large scale, efficient synthesis of 9-unsubstituted dipyrrinone
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9-Unsubstituted dipyrrinone 8, the useful precursor for the synthesis of biliverdins, bilirubins, and other bile pigments, was synthesized in large scale and high yield starting from acetaldehyde and nitroethane in eight steps with overall yield 10%. The key intermediate 3,4-dimethyl-2-ethoxycarbonylpyrrole 3 was synthesized via Zard-Barton's method in high yield.
- Chen, Qingqi,Wang, Tianyu,Zhang, Yi,Wang, Qiuan,Ma, Jinshi
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- New open-chain tetrapyrroles as chromophores in the plant photoreceptor phytochrome
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A series of six open-chain tetrapyrroles has been synthesized and used as chromophores for the plant photoreceptor protein phytochrome. The novel chromophores vary in the size of substituents 17 and 18 at ring D. This ring undergoes maximal conformational change upon light excitation (Z → E photoisomerization of the 15,16-double bond). Instead of methyl and vinyl substituents (positions 17, 18) as present in the native chromophore phytochromobilin, dimethyl, methyl and isopropyl, methyl and tert-butyl, ethyl and methyl, vinyl and methyl, and isopropyl and methyl substituents have been generated. All novel chromophores assemble with the apoprotein. The obtained chromoproteins show hypsochromic shifts of the absorbance maxima by 10 nm maximally, compared to the native pigment, except for the 17-isopropyl-18- methyl-substituted compound which showed a 100 nm hypsochromic shift of selectively the Pr form. The assembly kinetics were slowed down in correlation to the increasing size of the substituents, with stronger effects for modified substituents at position 17. The thermal stability of the photoinduced Pfr form for the 18-isopropyl and the 18-tert butyl substituents was even greater than that of the native pigments. Those chromophores carrying substituents at position 17 larger than the methyl group (ethyl and isopropyl) showed a very low stability of the respective P fr forms. Time-resolved detection of the Pfr to Pfr conversion (laser-induced flash photolysis) revealed a slower formation of the Pfr form for those chromophores carrying larger substituents at position 18, whereas the rise and decay kinetics of the early intermediates are only moderately changed. Introduction of larger substituents at position 17 (ethyl, vinyl, and isopropyl) causes drastic changes in the kinetics; in particular the formation of the first thermally stable intermediate, I 700, is significantly slowed, making a detection of its rise possible.
- Robben, Uwe,Lindner, Ingo,Gaertner, Wolfgang
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supporting information; experimental part
p. 11303 - 11311
(2009/02/05)
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- Intermolecularly hydrogen-bonded dimeric helices: tripyrrindiones
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A rare and unusual class of tripyrrolic compounds, violet-colored tripyrrin-1,14-diones, can be prepared easily and in moderately high yields from base (piperidine)-catalyzed condensation of 3-pyrrolin-2-ones with 2,5-diformylpyrroles. Dipyrrinones adopt the all-syn-Z conformation leading to helical, lock-washer like structures, which form dimers that are held together by intermolecular hydrogen bonds in nonpolar solvents and in the crystal. Strong bathochromic spectral shifts of the tripyrrindione ~480 nm long wavelength UV-visible absorption band are seen with added base: DBU, 615 nm; TFA, 573 nm; and Zn(OAc)2, 586 nm.
- Roth, Steven D.,Shkindel, Tetyana,Lightner, David A.
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p. 11030 - 11039
(2008/02/12)
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- Regiocontrolled synthesis of pyrrole-2-carboxaldehydes and 3-pyrrolin-2-ones from pyrrole Weinreb amides
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A regiocontrolled synthesis of 3,4-disubstituted pyrrole-2-carboxaldehydes was completed in two steps from acyclic starting materials. A Barton-Zard pyrrole synthesis between N-methoxy-N-methyl-2-isocyanoacetamide and α-nitroalkenes or β-nitroacetates provided N-methoxy-N-methyl pyrrole-2-carboxamides (pyrrole Weinreb amides), which were converted into the corresponding pyrrole-2-carboxaldehydes by treatment with lithium aluminum hydride. A regioselective oxidation of the pyrrole-2-carboxaldehydes gave the corresponding 3,4-disubstituted 3-pyrrolin-2-ones.
- Coffin, Aaron R.,Roussell, Michael A.,Tserlin, Elina,Pelkey, Erin T.
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p. 6678 - 6681
(2007/10/03)
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- A facile synthesis of 3,4-disubstituted-1,2-dihydro-5H-pyrrol-2-ones
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A facile and efficient method for the synthesis of 3,4-disubstituted-1,2- dihydro-5H-pyrrol-2-ones 8a,c-f is reported. The method involves the hydrogenation of cyanohydrins of 2-alkyl-3-oxobutyric acid alkyl esters 1a-f, over Raney Ni at 50 psi to furnish hitherto unknown aminoacetyl intermediates 6a-f in quantitative yields which are cyclised to the targeted compounds.
- Bhandari, Kalpana,Sharma
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p. 2467 - 2470
(2007/10/03)
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- Synthesis and unusual properties of expanded bilirubin analogs
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Pentapyrrole analogs of bilirubin and biliverdin have been prepared along with corresponding analogs where two dipyrrinones are attached to p-xylyl and m-xylyl groups. As determined by spectroscopic analysis and molecular modelling, the 'expanded' yellow
- Nogales, Daniel F.,Timothy Anstine,Lightner, David A.
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p. 8579 - 8596
(2007/10/02)
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- SYNTHESIS AND UNUSUAL PROPERTIES OF C(10)-gem-DIMETHYL BILIRUBIN ANALOGS
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The characteristic thermodynamically-favored intramolecularly hydrogen-bonded conformation adopted by bilirubin pigments is destabilized by substituting methyl groups on the C(10) central methylene.These methyl groups impose conformation-destabilizing methyl-methylene non-bonded steric interactions with the propionic acid β-CH2 groups at C(8) and C(12) when the propionic acids are engaged in intramolecular hydrogen bonding with the opposing dipyrrinones.Amphiphilic 10,10-dimethylbilirubins (1) and (2) are found to be more polar, but also more soluble than the parents (3) and (4) in organic solvents; yet, 1H-NMR studies in non-polar solvents indicate that a deformed but folded, intramolecularly hydrogen-bonded conformation is retained.The dimethyl esters of 10,10-dimethylbilirubins 1 and 2 did not exhibit the typical strong tendency of bilirubin dimethyl esters to form intermolecular hydrogen bonds in non-polar solvents such as chloroform and benzene.
- Xie, Meiqiang,Lightner, David A.
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p. 2185 - 2200
(2007/10/02)
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- Exciton Coupling from Dipyrrinone Chromophores
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2,3,7,8-Tetramethyl-(10H)-dipyrrin-1-one-9-carboxylic acid and p-(dimethylamino)benzoic acid are reacted separately with (1R,2R)-cyclohexanediol to form the corresponding diesters (1 and 3, respectively).These diesters exhibit intense bisignate circular dichroism (CD) spectra characteristic of exciton coupling and show a negative exciton chirality: Δεmax408 -122.5, Δεmax360 +95 (1 in CH2Cl2) and Δεmax318 -88.5 , Δεmax292 +41.5 (3 in CH2Cl2).In (CH3)2SO solvent the Cotton effect signs become inverted for the bis(dipyrrinone ester) but remain unchanged for the bis.
- Byun, Young-Seok,Lightner, David A.
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p. 6027 - 6033
(2007/10/02)
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- Synthesis and photochemical reactivity of bilirubin model compounds
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The bilirubin model compounds 1, 2 and 3 were prepared in good yield.The photochemistry of 1, 2 and 3, which all have the 4Z,15Z form, was investigated; they show a Z-E isomerisation to the 4Z,15E and the 4E,15E isomers.Unlike the isomers of 1, those of the compounds 2 and 3, could be isolated in a pure form.
- Groot, J. A. de,Steen, R. van der,Fokkens, R.,Lugtenburg, J.
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- Synthesis and photoisomerisation of 2,3,17,18,23-pentamethyl-10,23-dihydro 1,19--bilindione, an unsymmetrical bilirubin model compound
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The unsymmetrical bilirubin model compound 2,3,17,18,22-pentamethyl-10,23-dihydro-1,19--bilindione 1c has been prepared in good yield.Irradiation of 1c leads to a photostationary state which contains three photoproducts in addition to the starting material.The photoproducts has been isolated and fully characterized as the three possible geometric isomers of 1c.Short irradiation of each of the photoisomers shows that a one-photon one-double-bond isomerisation takes place.
- Groot, J. A. de,Steen, R. van der,Fokkens, R.,Lugtenburg, J.
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p. 219 - 223
(2007/10/02)
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