- Synthesis of 2,2-dialkyl chromanes by intramolecular Ullmann C–O coupling reactions toward the total synthesis of D-α-tocopherol
-
The complete synthesis of D-α-tocopherol was achieved using our developed-Ullmann C–O coupling reaction as a key reaction. The synthesis of the core structure of D-α-tocopherol, which is a chiral chromane, has never been reported using intramolecular Ullmann C–O coupling reactions owing to the low reactivity of electron-rich iodoarenes with tertiary alcohols. Because the developed intramolecular C–O coupling reactions prefer electron-rich iodoarenes with tertiary alcohols, we successfully synthesized the chiral chromane core and achieved the total synthesis of D-α-tocopherol.
- Tsubogo, Tetsu,Aoyama, Saki,Takeda, Rika,Uchiro, Hiromi
-
p. 843 - 846
(2018/09/10)
-
- BORYL ETHERS, CARBONATES, AND CYCLIC ACETALS AS OXIDATIVELY-TRIGGERED DRUG DELIVERY VEHICLES
-
A compound, or a pharmaceutically acceptable salt thereof, having a structure of Formula (I), wherein L is a cleavable linker group; X is a cargo moiety-containing group; and R1 and R2 are each independently hydrogen, alkyl, or substituted alkyl; or R1 and R2 together form a boronic ester ring or a substituted boronic ester group.
- -
-
Page/Page column 27; 28
(2018/03/28)
-
- Alcohol, Aldehyde, and Ketone Liberation and Intracellular Cargo Release through Peroxide-Mediated α-Boryl Ether Fragmentation
-
α-Boryl ethers, carbonates, and acetals, readily prepared from the corresponding alcohols that are accessed through ketone diboration, react rapidly with hydrogen peroxide to release alcohols, aldehydes, and ketones through the collapse of hemiacetal intermediates. Experiments with α-boryl acetals containing a latent fluorophore clearly demonstrate that cargo can be released inside cells in the presence of exogenous or endogenous hydrogen peroxide. These experiments show that this protocol can be used for drug activation in an oxidative environment without generating toxic byproducts.
- Hanna, Ramsey D.,Naro, Yuta,Deiters, Alexander,Floreancig, Paul E.
-
supporting information
p. 13353 - 13360
(2016/10/22)
-
- Versatile approach to α-alkoxy carbamate synthesis and stimulus-responsive alcohol release
-
A series of α-alkoxy carbamates that cleave under mild conditions to release alcohols has been synthesized through a multicomponent process. The relationship between structural features in these compounds and the rate of alcohol release in the presence of basic hydrogen peroxide has been studied. The preparation of carbamates that cleave under other conditions has been demonstrated.
- Mosey, R. Adam,Floreancig, Paul E.
-
supporting information
p. 7980 - 7985
(2013/06/27)
-
- Mesoporous and hexagonally ordered CuAl-SBA-15-catalyzed tandem C-C and C-O bond formation between phenols and allylic alcohols
-
A novel mesoporous catalyst, CuAl-SBA-15, with a hexagonally ordered porous structure prepared via a soft-templating approach in a highly acidic medium is used for tandem C-C and C-O bond formation between phenols and allylic alcohols to afford a variety of dihydrobenzopyrans in good yields. The catalyst is also found to be highly active for the synthesis of vitamin E and can be recycled several times without significant loss of its activity.
- Varghese, Shaji,Anand, Chokkalinkam,Dhawale, Dattatray,Mano, Ajayan,Balasubramanian, Veerappan V.,Raj, George Allen Gnana,Nagarajan, Samuthira,Wahab, Mohammad A.,Vinu, Ajayan
-
p. 5656 - 5659
(2012/10/29)
-
- InIII-catalysed tandem C-C and C-O bond formation between phenols and allylic acetates
-
Indium triflate catalysed tandem allylation-intramolecular hydroalkoxylation was efficiently carried out by using 1 mol-% of the catalyst under mild conditions to afford the dihydrobenzopyran ring system (chroman-type structure) in good yields. Kinetic, mechanistic and theoretical studies are also presented. Tandem allylation-intramolecular hydroalkoxylation carried out in the presence of an indium catalyst (1 mol-%) under mild conditions provides the dihydrobenzopyranring system in good yields. Kinetic, mechanistic and theoretical studies are presented.
- Vece, Vito,Ricci, Jeremy,Poulain-Martini, Sophie,Nava, Paola,Carissan, Yannick,Humbel, Stephane,Dunach, Elisabet
-
supporting information; experimental part
p. 6239 - 6248
(2010/12/29)
-
- Hybrid-increased radical-scavenging activity of resveratrol derivatives by incorporating a chroman moiety of vitamin e
-
A winning combination: Resveratrol derivatives incorporating a chroman moiety of vitaminE were constructed, resulting in the remarkable enhancement in tris(2,4,6-trichloro-3,5-dinitrophenyl)methyl radical (HNTTM)-scavenging activity as compared with the parent molecules (see scheme). Reaction kinetic analysis, oxidative product identification, and redox potential determination demonstrate that the reaction is governed by a sequential proton-loss electron-transfer (SPLET) mechanism.
- Yang, Jie,Liu, Guo-Yun,Lu, Dong-Liang,Dai, Fang,Qian, Yi-Ping,Jin, Xiao-Ling,Zhou, Bo
-
supporting information; experimental part
p. 12808 - 12813
(2011/02/22)
-
- Synthesis of chromans via [3 + 3] cyclocoupling of phenols with allylic alcohols using a Mo/o-chloranil catalyst system
-
(Chemical Equation Presented) The combination of a molybdenum complex (CpMoCl(CO)3 or [CpMo(CO)3]2) and o-chloranil was used as a catalyst in the [3 + 3] cyclocoupling of phenols and allylic alcohols under microwave heating conditions. Substituted chromans were selectively obtained in moderate to good isolated yields.
- Yamamoto, Yoshihiko,Itonaga, Kouhei
-
supporting information; experimental part
p. 717 - 720
(2009/08/19)
-
- Antioxidant properties of natural and synthetic chromanol derivatives: Study by fast kinetics and electron spin resonance spectroscopy
-
(Chemical Equation Presented) Chromanol-type compounds act as antioxidants in biological systems by reduction of oxygen-centered radicals. Their efficiency is determined by the reaction rate constants for the primary antioxidative reaction as well as for disproportionation and recycling reactions of the antioxidant-derived radicals. We studied the reaction kinetics of three novel chromanols: cis- and trans-oxachromanol and the dimeric twin-chromanol, as well as ubichromanol and ubichromenol, in comparison to α-tocopherol and pentamethylchromanol. The antioxidant-derived radicals were identified by optical and electron spin resonance spectroscopy (ESR). The kinetics of the primary antioxidative reaction and the disproportionation of the chromanoxyl radicals were assessed by stopped-flow photometry in different organic solvents to simulate the different polarities associated with biomembranes. Furthermore, the reduction of the chromanoxyl radicals by ubiquinol and ascorbate was measured after laser-induced one-electron chromanol oxidation in ethanol and in a micellar system, respectively. The rate constants showed that twin-chromanol had better radical scavenging properties than α-tocopherol and a significantly slower disproportionation rate of its corresponding chromanoxyl radical. In addition, the radical derived from twin-chromanol is reduced by ubiquinol and ascorbate at a faster rate than the tocopheroxyl radical. Finally, twin-chromanol can deliver twice as many reducing equivalents, which makes this compound a promising new candidate as artificial antioxidant in biological systems.
- Gregor, Wolfgang,Grabner, Gottfried,Adelwoehrer, Christian,Rosenau, Thomas,Gille, Lars
-
p. 3472 - 3483
(2007/10/03)
-
- Effects of magnesium ion on kinetic stability and spin distribution of phenoxyl radical derived from a vitamin E analogue: Mechanistic insight into antioxidative hydrogen-transfer reaction of vitamin E
-
The phenoxyl radical 1. of a vitamin E analogue, generated by the reaction of 2,2,5,7,8-pentamethylchroman-6-ol (1H) with 2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl (DPPH.) or galvinoxyl (G.), was significantly stabilized by the presence of Mg2+. Addition of Mg2+ into a solution of 1. resulted in a red shift of the absorption band of 1. as well as a decrease in the g value of the EPR spectrum of 1., indicating a complex formation between 1. and Mg2+. The complexation between the phenoxyl radical and Mg2+ significantly retards the disproportionation reaction of 1. by electronic repulsion between the metal cation and a generated organic cation (1+), leading to stabilization of the organic radical species. No effect of Mg2+ on the rate of hydrogen atom transfer from 1H to DPPH. or to G. was observed, suggesting that the hydrogen-transfer reaction between 1H and DPPH. or G. proceeds via a one-step hydrogen atom transfer mechanism rather than electron-transfer followed by proton transfer.
- Nakanishi, Ikuo,Fukuhara, Kiyoshi,Shimada, Tomokazu,Ohkubo, Kei,Iizuka, Yuko,Inami, Keiko,Mochizuki, Masataka,Urano, Shiro,Itoh, Shinobu,Miyata, Naoki,Fukuzumi, Shunichi
-
p. 1520 - 1524
(2007/10/03)
-
- Stability and reactivity of aryloxyl radicals derived from a novel antioxidant BO-653 and related compounds. Effects of substituent and side chain in solution and membranes
-
2,3-Dihydro-5-hydroxy-2,2-dipentyl-4,6-di-tert-butylbenzofuran (BO-653) is a novel antioxidant designed as a drug for inhibition of lipid peroxidation in vivo. To understand the dynamics of action of BO-653 as an antioxidant, the effects of substituents and side chains on the stability and reactivity of the BO-653 derived radical were studied and compared with the aryloxyl radicals derived from related compounds including α-tocopherol. The rate constants for the reactions of the aryloxyl radicals with themselves, lipid, hydroperoxide, and ascorbate were measured with a stopped-flow electron spin resonance (ESR) spectroscope equipped with a rapid mixing device. The ortho substituents exerted profound effects on the rate of bimolecular decay reactions and the reaction with ascorbic acid, while the effects on the reactions with methyl linoleate and tert-butyl hydroperoxide were much less significant. The side chain at the 2-position did not exert any effect in organic solution but the two pentyl side chains, when compared with two methyl side chains, diminished the apparent reactivities in the liposomal membranes.
- Watanabe, Akira,Noguchi, Noriko,Fujisawa, Akio,Kodama, Tatsuhiko,Tamura, Kunio,Cynshi, Osamu,Niki, Etsuo
-
p. 5438 - 5442
(2007/10/03)
-
- Reaction between phenols and isoprene under zeolite catalysis. Highly selective synthesis of chromans and o-isopentenylphenols
-
Chromans 3 and o-isopentenylphenols 4 are synthesized in satisfactory to good yields and selectivities by the reaction of phenols and isoprene in the presence of the commercially available acid faujasite zeolite HSZ-360.
- Bigi, Franca,Carloni, Silvia,Maggi, Raimondo,Muchetti, Chiara,Rastelli, Massimo,Sartori, Giovanni
-
p. 301 - 304
(2007/10/03)
-
- Oxidized diphenylheteroalkanes
-
Oxidized diphenylheteroalkanes of the formula I STR1 where R1 to R6 and A have the meanings specified in the description, and the preparation thereof are described. The substances are suitable for controlling diseases and as cosmetic agents.
- -
-
-
- Versatile synthesis of benzopyrans via ortho-Claisen rearrangement of allyl ethers
-
Benzopyrans can be efficiently synthesized by reacting a phenol and an allylic alcohol in a trifluoroacetic acid/water mixture under argon at room temperature. The procedure is widely applicable and allows benzopyrans to be synthesized rapidly.
- Ismail, Fyaz M. D.,Hilton, Mark J.,Stefmovic, Marijan
-
p. 3795 - 3796
(2007/10/02)
-
- Reactions of a Hydroperoxide, 8a-Hydroperoxy-2,2,5,7,8-pentamethylchroman-6(8aH)-one, Derived from a Vitamine E Model Compound: Dimerization and X-Ray Crystal Structure
-
A hydroperoxide, 8a-hydroperoxy-2,2,5,7,8-pentamethylchroman-6(8aH)-one, was obtained from the reaction of a vitamin E model compound, 2,2,5,7,8-pentamethylchroman-6-ol, with singlet oxygen, and was dimerized in toluene in the presence of lead tetraacetate to give bis(2,2,5,7,8-pentamethyl-6-oxo-6,8a-dihydrochroman-8a-yl) peroxide.The structures of the hydroperoxide and peroxide were confirmed by X-ray crystallographic analysis, and their properties were examined.
- Matsumoto, Shigenobu,Matsuo, Mitsuyoshi,Iitaka, Yoichi
-
p. 601 - 641
(2007/10/02)
-
- Organic Synthesis with sulfones. XLI. Nucleophilic substitution of allylic sulfones
-
The sulfonyl group in allylic sulfones can be displaced by a variety of nucleophiles.The reaction is particularly easy with tertiary sulfones, i.e. bearing no hydrogen atoms at the α-position.Lewis acids catalyse the displacement reaction.
- Julia, Marc,Nel, Maurice,Uguen, Daniel
-
p. 487 - 492
(2007/10/02)
-