scholarly journals Concerning the structure of photobilirubin II

1982 ◽  
Vol 201 (1) ◽  
pp. 179-188 ◽  
Author(s):  
M S Stoll ◽  
N Vicker ◽  
C H Gray ◽  
R Bonnett
Keyword(s):  
Double Bond ◽  
Starting Material ◽  
Vinyl Group

Evidence is presented which supports the postulate that the photobilirubins IIA and IIB are diastereoisomers in which the C-3 vinyl group has cyclized intramolecularly. The evidence comes principally from proton n.m.r. spectroscopy at 400 MHz and from chemical considerations. The cyclic structures require the E-configuration at the C-4 double bond in the precursor; this is the first structural evidence for the Z leads to E isomerization in bilirubin and supports the view that the precursor (photobilirubin IA or IB) is (4E, 15Z)-bilirubin. Brief irradiation of photobilirubin II gives bilirubin, a new compound (photobilirubin III) and unchanged starting material. The various photoisomers are discussed in terms of their inter-relationships and biological fates.

scholarly journals Intramolecular Cyclization of Ruthenium Vinylidene Complexes with a Tethering Vinyl Group:  Facile Cleavage and Reconstruction of the C−C Double Bond

2007 ◽  
Vol 129 (48) ◽  
pp. 14974-14980 ◽  
Author(s):  
Cheng ◽  
Yi-Chun Kuo ◽  
Shu-Hao Chang ◽  
Ying-Chih Lin ◽  
Yi-Hong Liu ◽  
...  
Keyword(s):  
Double Bond ◽  
Intramolecular Cyclization ◽  
Vinylidene Complexes ◽  
Vinyl Group

scholarly journals Lead tetraacetate oxidation of the Diels-Alder adduct of 7-dehydrocholestryl acetate with maleic anhydride

2000 ◽  
Vol 65 (3) ◽  
pp. 147-156 ◽  
Author(s):  
Lidija Bondarenko-Gheorghiu ◽  
Ljubinka Lorenc ◽  
Mihailo Mihailovi]
Keyword(s):  
Double Bond ◽  
Maleic Anhydride ◽  
Total Yield ◽  
Diels Alder ◽  
Lead Tetraacetate ◽  
Starting Material ◽  
Large Excess ◽  
Pyridine Solution ◽  
Alder Adduct

The Diels-Alder adduct (3), obtained by cycloaddition of 7-dehydrocholesteryl acetate (1) and maleic anhydride (2), was heated at ca. 90?C with a large excess of lead tetraacetate in pyridine solution for 5h. Under these conditions, compound 3 underwent lactonization with the participation of the olefinic ?6-double bond to give two isomeric monolactone derivatives, 9 and 10 (in a total yield of ca. 6%), and the bislactone product 11 (in 11.5% yield). The starting material was recovered in 36% yield.

Synthesis of isoxazoline-linked chlorins and their in vitro cell viabilities

2010 ◽  
Vol 14 (10) ◽  
pp. 859-865 ◽  
Author(s):  
Jin-Jun Wang ◽  
Jia-Zhu Li ◽  
Yun-Wei Li ◽  
Judit Jakus ◽  
Young Key Shim
Keyword(s):  
Photodynamic Therapy ◽  
Cell Line ◽  
Starting Material ◽  
Nitrile Oxide ◽  
Dipolar Cycloaddition ◽  
Mouse Sarcoma ◽  
Pyropheophorbide A ◽  
Vinyl Group ◽  
Vitro Effect

A concise synthesis of isoxazoline-linked chlorins is described. This approach is carried out from methyl pyropheophorbide-a as the starting material via 1,3-dipolar cycloaddition of a vinyl group on the periphery with nitrile oxide to give regioselective products with excellent yields. This method represents an extensive and efficient entry into the functionalization of chlorins with a chlorophyll-α skeleton. Moreover, we have examined a preliminary in vitro effect of these new derivatives on mouse sarcoma S-180 cell line in photodynamic therapy.

The transformation of levopimaric acid into warburganal

1988 ◽  
Vol 66 (7) ◽  
pp. 1675-1685 ◽  
Author(s):  
William A. Ayer ◽  
Francisco X. Talamas
Keyword(s):  
Double Bond ◽  
Formic Acid ◽  
Sodium Methoxide ◽  
Resin Acid ◽  
Starting Material ◽  
Protecting Group ◽  
Methyl Group ◽  
Levopimaric Acid

The chiral resin acid levopimaric acid (1), isolated from pine oleoresin, is used as a starting material for the synthesis of (−)-warburganal (2). The synthesis proceeds via the endoperoxide of methyl levopimarate, which after ozonolysis, protection of the resulting aldehyde function, reduction, and treatment with sodium methoxide provides the tetranorditerpenoid 12a. The hemiacetal 12a is then transformed to a mixture of hemithioacetals. At this point the carbomethoxyl group at C-4 is reduced to a methyl group, and then a C-11, C-12 double bond is introduced. Ozonolysis followed by elimination of formic acid provides a mixture of olefins (27) that is hydroxylated at C-9. Removal of the protecting group then gives (−)-warburganal (2). The sequence requires 15 steps and the overall yield from levopimaric acid to warburganal is 2.7%.

scholarly journals Intramolecular Metathesis of a Vinyl Group with Vinylidene CC Double Bond in Ru Complexes

2005 ◽  
Vol 127 (51) ◽  
pp. 18037-18045 ◽  
Author(s):  
Yung-Sheng Yen ◽  
Ying-Chih Lin ◽  
Shou-Ling Huang ◽  
Yi-Hung Liu ◽  
Hui-Ling Sung ◽  
...  
Keyword(s):  
Double Bond ◽  
Ru Complexes ◽  
Vinyl Group

Utilisation de la méthode de Wittig pour la synthèse de vinyl-2 aziridines N-substituées

1976 ◽  
Vol 54 (10) ◽  
pp. 1582-1589 ◽  
Author(s):  
Daniel Borel ◽  
Yvonne Gelas-Mialhe ◽  
Roger Vessière
Keyword(s):  
Double Bond ◽  
Nmr Spectra ◽  
Starting Material

Several 2-vinylaziridines were prepared by treating N-substituted 2-acylaziridines with phosphoranes. The stereochemistry of the ring and the double bond of the products was established from a study of their nmr spectra. The geometry of the starting material 2-acylaziridine is conserved in the 2-vinylaziridine formed. [Journal translation]

Electrophilic additions to 10β-vinyl cholestane derivatives

1983 ◽  
Vol 48 (10) ◽  
pp. 2994-3019 ◽  
Author(s):  
Pavel Kočovský ◽  
Ivo Starý ◽  
František Tureček ◽  
Vladimír Hanuš
Keyword(s):  
Reaction Mechanism ◽  
Double Bond ◽  
Hydroxyl Group ◽  
Acid Addition ◽  
Hypobromous Acid ◽  
Markovnikov Rule ◽  
Vinyl Group ◽  
Electrophilic Additions

Hypobromous acid addition to steroid dienes I-VI proceeds in four steps. The reaction commences by the attack on more reactive endocyclic double bond from the α-side yielding intermediary diaxial bromohydrins XXVIII, XXXIV, XL, XLIV, L and LVI via corresponding α-bromonium ions. The 10β-vinyl group of the bromohydrins then reacts with a second equivalent of the reagent forming transient 19-epimeric bromonium ions. The ions generated from I, II, V and VI are cleaved intramolecularly by the hydroxyl group, in accordance with the Markovnikov rule, giving rise to 19-epimeric dibromo epoxides XXXIa and XXXIIa, XXXVII and XXXVIII, LIIIa and LIVa, LIX and LX. By contrast, the ions generated from III and IV are cleaved in an anti-Markovnikov manner to yield dibromo epoxides XLII, XLVII and XLVIII. Products due to formation of a new C-C bond were not observed. The reaction mechanism and differences in the behaviour of the dienes I-VI are discussed.

THE OLEFINIC BOND IN GELSEMINE

1957 ◽  
Vol 35 (4) ◽  
pp. 301-304 ◽  
Author(s):  
Léo Marion ◽  
K. Sargeant
Keyword(s):  
Double Bond ◽  
Osmium Tetroxide ◽  
Catalytic Amount ◽  
Starting Material ◽  
Side Chain ◽  
Olefinic Bond ◽  
Sodium Metaperiodate ◽  
Exocyclic Methylene ◽  
Olefinic Double Bond ◽  
Methylene Group

The readily reducible double bond of gelsemine has been shown to be present in a vinyl side chain and not in an exocyclic methylene group as had been previously assumed. Oxidation of the olefinic double bond in N(a)-methylgelsemine with sodium metaperiodate in the presence of a catalytic amount of osmium tetroxide gave an aldehyde having one carbon less than the starting material. That the product was an aldehyde and not a ketone was proved (a) by conversion to an oxime which was readily dehydrated to a nitrile, and (b) by Wolff-Kishner reduction to a compound containing a C—CH3 group not present in the aldehyde itself.

Allergenic α-methylene-γ-butyrolactones. A one-carbon degradation of isoalantolactone via Pummerer rearrangement of sulfoxides

1979 ◽  
Vol 57 (2) ◽  
pp. 213-217 ◽  
Author(s):  
Jean-Pierre Corbet ◽  
Claude Benezra
Keyword(s):  
Double Bond ◽  
Starting Material ◽  
The Other ◽  
The One ◽  
Carbon Degradation

Isoalantolactone and α-methylene-γ-butyrolactone were separately treated with NaSPh, transformed into sulfoxides, and rearranged under Pummerer conditions (Ac2O + (CF3CO)2O). The Pummerer products were hydrolyzed, oxidized, and decarboxylated resulting in the formation of 13-norisoalantolactone (with migration of the exo-C(4) double bond into position C(4)—C(5)) on the one hand and of γ-butyrolactone on the other. The isomeric norisoalantolactone 17 is a starting material for the synthesis of 14C-labelled alantolactone, 18.

Silaheterocyclen, XIII Erzeugung und Cycloadditionsverhalten von 1,3-Diaza-2,4-disila-und 1.3-Disilacyclobutanen mit exocyclischer SiC-Doppelbindung Silaheterocycles, XIII / Formation and Cycloaddition Reactions of 1,3-Diaza-2,4-disila-and 1.3-Disilacyclobutanes Containing an Exocyclic SiC Double Bond

1992 ◽  
Vol 47 (2) ◽  
pp. 217-230 ◽  
Author(s):  
Norbert Auner ◽  
Erika Penzenstadler
Keyword(s):  
Double Bond ◽  
Diels Alder ◽  
Spiro Compound ◽  
Cycloaddition Reactions ◽  
Temperature Range ◽  
Vinyl Group ◽  
Trapping Agent

The silenes A and B are formed by reacting 1,3-ditbutyl-2,4-dichloro-2,4-divinyl-1,3-diaza- 2.4-disilacyclobutane (2) and 1,3-dichloro-2,4-dineopentyl-1,3-divinyl-1,3-disilacyclobutane (15) with LiBut in n-pentane in the temperature range from −10 to 0 °C. The reaction primarily leads to the corresponding α-lithioadducts (addition of LiBut to the vinyl group of 2 and 15), and with subsequent 1,2-LiCl elimination yields A and B as intermediates. A can be trapped by polar reagents Me3SiX (X = OMe, OSO2CF3) as well as by organic dienes which add across the Si = C bond; in the absence of a trapping agent the spiro compound 6 is isolated. The silenes A and B differ in their cycloaddition behaviour to butadienes, norbornadiene and cyclohexa-1,3-diene: Whereas for A the regioselective [2 + 2]-cycloaddition to yield monosilacyclobutane derivatives is preferred due to electronic reasons, the reaction of B leads mainly to Diels-Alder products. Thus, A is quite comparable in its reactivity to dichloroneopentylsilene, while B reacts like its diorgano substituted analogues R2Si = CHCH2But (R = Me, But or Ph).

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