- On the Products of Cholesterol Autoxidation in Phospholipid Bilayers and the Formation of Secosterols Derived Therefrom
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In homogenous solution, cholesterol autoxidation leads to a mixture of epimers of 5 primary products, whose concentrations vary in the presence/absence of antioxidants, such as vitamin E. Two of the products (5α-OOH and 6β-OOH) undergo Hock fragmentation
- Facey, Glenn A.,Pratt, Derek A.,Schaefer, Emily L.,Zielinski, Zosia A. M.,Zopyrus, Nadia
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supporting information
p. 2089 - 2094
(2020/01/24)
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- Gadolinium(III) Porpholactones as Efficient and Robust Singlet Oxygen Photosensitizers
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Construction of GdIIIphotosensitizers is important for designing theranostic agents owing to the unique properties arising from seven unpaired f electrons of the Gd3+ion. Combining these with the advantages of porpholactones with tun
- Ke, Xian-Sheng,Ning, Yingying,Tang, Juan,Hu, Ji-Yun,Yin, Hao-Yan,Wang, Gao-Xiang,Yang, Zi-Shu,Jie, Jialong,Liu, Kunhui,Meng, Zhao-Sha,Zhang, Zongyao,Su, Hongmei,Shu, Chunying,Zhang, Jun-Long
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p. 9676 - 9686
(2016/07/14)
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- Synthesis, Characterization, and Electronic Properties of Porphyrins Conjugated with N-Heterocyclic Carbene (NHC)-Gold(I) Complexes
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Porphyrins fused to peripheral N-heterocyclic carbenes (NHC) across two neighboring β,β-pyrrolic positions were used for the synthesis of different mono- and bis-carbenic gold(I) complexes. These studies also revealed how it is possible to modulate the re
- Longevial, Jean-Fran?ois,Langlois, Adam,Buisson, Antoine,Devillers, Charles H.,Clément, Sébastien,Van Der Lee, Arie,Harvey, Pierre D.,Richeter, Sébastien
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p. 663 - 672
(2016/03/25)
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- Comparison of photo-oxidation reactions in batch and a new photosensitizer-immobilized microfluidic device
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A glass microfluidic device has been functionalized with photoactive porphyrins for performing reactions which are mediated by singlet molecular oxygen. The resulting device was used to investigate the photochemical oxidation of cholesterol, α-terpinene, and citronellol under flow conditions, and the results were compared with similar batch reactions.
- Lumley, Emily K.,Dyer, Charlotte E.,Pamme, Nicole,Boyle, Ross W.
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supporting information
p. 5724 - 5727
(2013/01/15)
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- Cholesterol hydroperoxides generate singlet molecular oxygen [O 2(1Δg)]: Near-IR emission, 18O-labeled hydroperoxides, and mass spectrometry
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In mammalian membranes, cholesterol is concentrated in lipid rafts. The generation of cholesterol hydroperoxides (ChOOHs) and their decomposition products induces various types of cell damage. The decomposition of some organic hydroperoxides into peroxyl
- Uemi, Miriam,Ronsein, Graziella E.,Prado, Fernanda M.,Motta, Flavia D.,Miyamoto, Sayuri,Medeiros, Marisa H. G.,Di Mascio, Paolo
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experimental part
p. 887 - 895
(2012/04/11)
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- A new approach to N-phenylquinolino[2,3,4-at]porphyrins: Electrochemical and photochemical studies
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A new route to N-phenylquinolino[2,3,4-at]porphyrins is described and the electrochemical and photochemical properties of the synthesized derivatives were investigated. The electrochemical studies (cyclic voltammetry and rotating disk voltammetry) of the
- Pereira, Ana M.V.M.,Neves, Maria G.P.M.S,Cavaleiro, José A.S.,Gisselbrecht, Jean-Paul,Jeandon, Christophe,Ruppert, Romain
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experimental part
p. 575 - 582
(2012/05/05)
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- Photochemistry of bacteriochlorophylls in human blood plasma: 2. Reaction mechanism investigated by product analysis and deuterium isotope effect
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Transmetalated (Pd) bacteriochlorophyll derivatives are currently being clinically tested as sensitizers for photodynamic therapy. Protocols using short delay times between injection and irradiation generate interest in the photochemistry of these pigments in the blood. Using near-infrared irradiation where these pigments absorb strongly, we have studied the mechanism of photo-oxidation in two lipoprotein fractions, low- and high-density lipoproteins, derived from human blood plasma that preferentially accumulate these pigments (Dandler et al. [2009] Photochem. Photobiol., 85, in press). Using quenchers of reactive oxygen species, and chemical reporters, in particular peroxides generated from cholesterol as an inherent component of the lipoproteins, a Type II mechanism generating singlet oxygen has been demonstrated for Pd- and Zn-bacteriopheophorbides. In homogeneous systems, accelerated bleaching in D2O, compared with H2O, supports this mechanism. An unusual deuterium isotope effect was observed, by contrast, in heterogeneous amphiphilic-water systems. In the early phase, and under high oxygen concentrations, again a positive D-isotope effect is observed which later, in a second phase, is reversed to a negative D-isotope effect. The latter cannot be explained by heterogeneous pigment populations in the amphiphilic system; we, therefore, conclude a mechanistic switch, and discuss a possible mechanism.
- Dandler, Joerg,Wilhelm, Brigitte,Scheer, Hugo
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experimental part
p. 342 - 352
(2010/10/02)
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- Synthesis, characterization, and electrochemical studies of new π-Extended metalloporphyrins
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A doubly fused porphyrin has been synthesized by two successive cyclization reactions. The first meso-phenyl group was fused, by an intramolecular Cadogan reaction leading to an enamine-functionalized porphyrin. After Vilsmeier-Haack formylation of the ni
- Jimenez, Angel J.,Jeandon, Christophe,Gisselbrecht, Jean-Paul,Ruppert, Romain
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supporting information; experimental part
p. 5725 - 5730
(2010/03/01)
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- The ratio of cholesterol 5,6-secosterols formed from ozone and singlet oxygen offers insight into the oxidation of cholesterol in vivo
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Ongoing efforts to unravel the origins of the cholesterol 5,6-secosterols (1a and 1b) in biological systems have revealed that the two known chemical routes to these oxysterols, ozonolysis of cholesterol (3) and Hock-cleavage of 5-α-hydroperoxycholesterol (4a), are distinguishable based upon the ratio of the hydrazone derivatives (2a and 2b) formed in each case and this ratio offers an insight into the chemical origin of the secosterols in vivo. The Royal Society of Chemistry 2009.
- Wentworth, Anita D.,Song, Byeong-Doo,Nieva, Jorge,Shafton, Asher,Tripurenani, Sangeetha,Wentworth Jr., Paul
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supporting information; experimental part
p. 3098 - 3100
(2009/12/01)
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- Locked π-expanded chlorins in two steps from simple tetraarylporphyrins
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(Chemical Equation Presented) Upon tandem Reformatsky reaction, easily accessible porphyrinic ketones give "locked" chlorinic diester. Both ketones and diesters, as bases or palladium complexes, efficiently generate singlet dioxygen, as demonstrated by tr
- Fouchet, Julien,Jeandon, Christophe,Ruppert, Romain,Callot, Henry J.
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p. 5257 - 5260
(2007/10/03)
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- Singlet-oxygen ene reaction with 3β-substituted stigmastanes. An alternative pathway for the classical Schenck rearrangement
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The course of the singlet-oxygen ene reaction with stigmasta-5,22-dienes may be controlled if in the substrate a good leaving group as substituent is present at 3-C. Thus when the 5α-hydroperoxystigmasta-5,22-diene is formed instead of the well known allylic rearrangement to yield the 7α-hydroperoxystigmasta-5,22-diene isomer an intramolecular nucleophilic substitution can then occur yielding 5α-hydroxystigmasta-6,22-dien-3-one. Various stigmasta-5,22-dienes were chosen to elucidate which feature of the stigmastane is necessary to control the course of the reaction. Thus, 3β-F, 3β-Cl, 3β-Br, 3β-I and 3α-Br-stigmasta-5,22-dienes were firstly prepared and fully characterized in order to study their reaction with 1O2 under different experimental conditions. 3β-Acetoxy- and 3β-mesyloxy-stigmasta-5,22-diene derivatives were also prepared and studied.
- Ponce, Maria A.,Ramirez, Javier A.,Galagovsky, Lydia R.,Gros, Eduardo G.,Erra-Balsells, Rosa
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p. 2351 - 2357
(2007/10/03)
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- Mass spectrometry characterization of the 5α-, 7α-, and 7β-hydroxy derivatives of β-sitosterol, campesterol, stigmasterol, and brassicasterol
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The 5α-hydroperoxides of β-sitosterol, campesterol, stigmasterol, and brassicasterol were obtained by photooxidation of the respective sterols in pyridine in the presence of hematoporphyrine as sensitizer. The reduction of the hydroperoxides gives the corresponding 5α-hydroxy derivatives. The 7α- and 7β-hydroperoxides of the sterols were obtained by allowing an aliquot of the 5α-hydroperoxides to isomerize to 7α-hydroperoxides, which in turn epimerize to 7β-hydroperoxides. The reduction gave the corresponding 7α- and 7β-hydroxy derivatives. The 5α-, 7α-, and 7β-hydroxy derivatives of β-sitosterol, campesterol, stigmasterol, and brassicasterol were identified by comparing thin-layer chromatography mobilities, specific color reactions, and mass spectral data with those of the corresponding hydroxy derivatives of cholesterol, which were synthesized in the same manner. The phytosterols had the same behavior to photooxidation as cholesterol and, moreover, the different phytosterols photooxidized at about the same rate. The mass spectra of the trimethylsilyl ethers of the hydroxy derivatives of the phytosterols investigated and of the corresponding hydroxy derivatives of cholesterol have the same fragmentation patterns and similar relative ion abundances.
- Bortolomeazzi, Renzo,De Zan, Michela,Pizzale, Lorena,Conte, Lanfranco S.
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p. 3069 - 3074
(2007/10/03)
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- Catalysis of Ene Reactions by Lithium Perchlorate
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The ene reaction of some allylic hydrocarbons, and the metallo-ene reaction of some allyltin compounds, with 1,3,4-triazoline-2,5-diones or with diethyl azodicarboxylate as enophiles, in diethyl ether are strongly catalysed by lithium perchlorate.Azobenzene, on the other hand, reacts slowly with alkyltin compounds, undergoing hydrostannation.The reaction of cholesterol or of tributylallyltin with singlet oxygen is subject to a smaller catalysis.
- Davies, Alwyn G.,Kinart, Wojciech J.
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p. 2281 - 2284
(2007/10/02)
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- The mechanisms of the rearrangements of allylic hydroperoxides: 5α-hydroperoxy-3β-hydroxycholest-6-ene and 7α-hydroperoxy- 3β-hydroxycholest-5-ene
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The rearrangement of 5α-hydroperoxy-3β-hydroxycholest-6-ene in solution under 18O2, gives isotopically normal 7α-hydroperoxy-3β-hydroxycholest-5-ene, whereas the epimerization of this product to give 7β-hydroperoxy-3β-hydroxycholest-5-ene involves incorporation of 73-83% of 18O2 into the hydroperoxy group. These two reactions proceed through the corresponding hydroperoxyl radicals, which have different e.s.r. spectra and which therefore must exist as separate and distinct species. The former reaction shows a first-order dependence on hydroperoxide concentration, and a half-order dependence on t-butyl hyponitrite which was added as an initiator. It is suggested that the first reaction involves a sigmatropic [2,3]-rearrangement, whereas the second reaction proceeds through a dissociative mechanism.
- Beckwith, Athelstan L. J.,Davies, Alwyn G.,Davison, Ian G. E.,Maccoll, Allan,Mruzek, Margaret H.
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p. 815 - 824
(2007/10/02)
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- PHOTOOXYDATIONS PAR TRANSFERT D'ELECTRON. PHOTOOXIGENATIONS SENSIBILISEES PAR LE DICYANO-9,10 ANTHRACENE. FORMATION DE O2. ET (1)O2.
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Photooxidation of electron-rich compounds (donor) sensitized by 9,10-dicyanoanthracene (DCA, acceptor) gives evidence for the effect of solvent polarity on the photochemical reaction mechanism.The chemical outcome can be connected with the fluorescence data.The formation of O2. and (1)O2 proceeds from a charge transfer complex between the donor and the acceptor upon excitation.
- Santamaria, J.,Ouchabane, R.
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p. 5559 - 5566
(2007/10/02)
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