ScienceDirect Publication: Tetrahedron: Asymmetry
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Stereochemistry of terpene derivatives. Part 7: Novel rigidified amino acids ...
25 Jul 2010 at 1:43pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 24 July 2010
Kamila, Gajcy , Jolanta, P?kala , Bo?ena, Fr?ckowiak-Wojtasek , Tadeusz, Librowski , Stanis?aw, Lochy?ski
Several novel cyclopropyl-rigidified ?- and ?-amino acids 3?4 have been prepared starting from monoterpene (+)-3-carene 2. These compounds are proposed as chiral analogues of ?-aminobutyric acid (GABA) 1 and are expected to be of interest as potential inhibitors of GABA receptors.
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Enantioselective hydrogenation of indoles derivatives catalyzed by Walphos/rh...
25 Jul 2010 at 1:43pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 24 July 2010
Anna M., Maj , Isabelle, Suisse , Catherine, Méliet , Francine, Agbossou-Niedercorn
The enantioselective hydrogenation of indole esters has been carried out efficiently in the presence of a rhodium catalyst modified by Walphos-type chiral ligands. The addition of a base can be beneficial in some catalytic conditions.
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Bioreduction of ?-carboline imines to amines employing Saccharomyces bayanus
25 Jul 2010 at 1:43pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 24 July 2010
Marlene, Espinoza-Moraga , Tania, Petta , Marco, Vasquez-Vasquez , V. Felipe, Laurie , Luis A.B., Moraes , ...
?-Carboline imine reductions mediated by Saccharomyces bayanus have been described achieving moderate to good enantiomeric excesses of the amine products. The enantiomeric excesses of the bioreduction showed a dependence on the imine substituents. Compounds presenting C1?C11 aliphatic substituent groups afforded amines with an (S)-configuration, whereas C15 and higher aliphatic- and aromatic-substituted ?-carboline imines achieved inversion of the configuration in the final (R)-2 amine products. Based on this data, a model for the Saccharomyces reduction is proposed.
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Synthesis of novel carbohydrate-based iminophosphinite ligands in Pd-catalyze...
25 Jul 2010 at 1:43pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 24 July 2010
Chao, Shen , Haijun, Xia , Hui, Zheng , Pengfei, Zhang , Xinzhi, Chen
A series of novel carbohydrate-based iminophosphinite ligands have been synthesized for the first time and successfully applied in Pd-catalyzed asymmetric allylic alkylation. The substituent effects on the catalytic reaction were also investigated, and 92% ee was achieved when the p-nitro-substituted ligand 10d was used.
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Pd(II)-catalyzed and diethylzinc-mediated asymmetric umpolung allylation of a...
25 Jul 2010 at 1:43pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 24 July 2010
Jia-Jun, Jiang , De, Wang , Wen-Feng, Wang , Zhi-Liang, Yuan , Mei-Xin, Zhao , ...
Chiral phosphine-Schiff base type ligand L3 prepared from (R)-(?)-2-(diphenylphosphino)-1,1?-binaphthyl-2?-amine was found to be a fairly effective chiral ligand for the Pd(II)-catalyzed and diethylzinc-mediated enantioselective umpolung allylation of aldehydes to give homoallylic alcohols in good yields, moderate enantioselectivities and high syn diastereoselectivities.
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Synthetic studies on cytotoxic macrolides cruentarens A and B: stereoselectiv...
23 Jul 2010 at 1:49pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 23 July 2010
Busam Ramalinga Vara, Prasad , Harshadas Mitaram, Meshram
A stereoselective synthesis of the C8?C19 segment of cruentarens A and B, cytotoxic natural products, has been accomplished. The key steps involve a stereoselective radical cyclization, stereospecific methylation of a ?, ?-epoxy acrylate, nucleophilic epoxide ring opening and a cis-Wittig olefination.
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Chiral synthons from campholenaldehyde: enantiospecific synthesis of diquinan...
23 Jul 2010 at 1:49pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 23 July 2010
Adusumilli, Srikrishna , Ghodke, Neetu
Enantiospecific syntheses of diquinane and linear triquinanes were accomplished, starting from the readily available ?-campholenaldehyde employing a Nazarov reaction as the key step.
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Stereoselective synthesis of 5,6-disubstituted 5,6-dihydro-1,10-phenanthrolin...
23 Jul 2010 at 1:49pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 23 July 2010
Giorgio, Chelucci , Claudia, Sanfilippo
The stereoselective synthesis of 5,6-disubstituted 5,6-dihydro-1,10-phenanthrolines and (5S,6S)-5,6-dihydroxy-5,6-dihydro-1,10-phenanthroline cyclic o-xylylene diether, a rare example of an axially constrained 2,2?-bipyridine is reported. The strategy to obtain such compounds is based on two highly efficient reactions, the Sharpless asymmetric dihydroxylation and the Ullmann intramolecular coupling.
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Association of biotin with silver (I) in solution: a circular dichroism study
23 Jul 2010 at 1:49pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 23 July 2010
Iryna, Goncharova , David, Sykora , Marie, Urbanová
A strong polymeric helical complex of Ag(I) with biotin, a water-soluble vitamin also called vitamin H or B7, has been described in the crystal phase, yet with missing spatial characteristic of its solution structure. In this work, the complexation of d-(+)-biotin with Ag+ in aqueous solution has been studied by means of circular dichroism spectroscopy and mass spectrometry with electrospray ionization in positive mode (MS-ESI+). For comparison, the spectra of the Nujol suspension of studied systems in the solid state were also measured. The results indicate that the Ag(I)?biotin complex has a helical arrangement of the biotin molecules in solution....
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Asymmetric dihydroxylation of drim-7-en-11-ol: synthesis of diastereomericall...
23 Jul 2010 at 1:49pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 23 July 2010
Pavel, Vlad , Elena, Gorincioi , Aculina, Aricu , Alic, Barba , Ada, Manzocchi , ...
The asymmetric dihydroxylation of drim-7-en-11-ol was studied in detail and diastereomerically pure driman-7?,8?,11- and driman-7?,8?,11-triols were prepared. Further elaboration of driman-7?,8?,11-triol afforded 14,15-bisnorlabd-7?,8?-isopropylidenedioxy-11,13-dione from which a novel chlorinated bisnorlabdanic compound (14,15-bisnorlabd-12-ene-12-chloro-8?,13-epoxy-7?-ol-11-one) and an unusual dichloro-derivative, 13,14,15,16-tetranorlabd-12-dichloro-7?-acetoxy-8?-ol-11-one, were obtained.
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Synthesis of a tetrasaccharide related to the triterpenoid saponin Bellisosid...
23 Jul 2010 at 1:49pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 23 July 2010
Santanu, Mandal , Nayan, Sharma , Balaram, Mukhopadhyay
A concise synthesis of a tetrasaccharide related to the triterpenoid saponins Bellisoside has been accomplished from commercially available monosaccharides through rational protecting group manipulations and stereoselective glycosylations. For the glycosylation reactions, H2SO4?silica has been successfully used as an alternative to conventional Lewis acids such as TfOH or TMSOTf. The target tetrasaccharide has been synthesized in the form of its p-methoxyphenyl glycoside which leaves scope for further glyco-conjugate formation through the selective deprotection of p-methoxyphenyl glycoside followed by trichloroacetimidate chemistry.
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Halogenative kinetic resolution of ?-aryloxy cyclic alcohols: chiral BINAP-me...
23 Jul 2010 at 1:49pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 23 July 2010
E.A., Jaseer , I., Karthikeyan , Govindasamy, Sekar
A series of optically active cyclic trans-?-aryloxy alcohols have been obtained by non-enzymatic kinetic resolution of the corresponding racemic aryloxy cyclic alcohols using commercially available (S)-BINAP and NCS by SN2 halogenation of a hydroxy group. The product, cis-?-aryloxy chlorides, was also obtained in optically active form with inversion of the stereochemistry.
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Stereoselective syntheses of polyhydroxylated azepane derivatives from sugar-...
23 Jul 2010 at 1:49pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 23 July 2010
Noe, Oña , Antonio, Romero , Carmen, Assiego , Claudia, Bello , Pierre, Vogel , ...
An approach to the synthesis of polyhydroxyazepane derivatives from sugar-based epoxyamides or epoxyalcohols, in which the total regioselective epoxide opening by nitrogen nucleophiles is the key step, is described. Thus, novel polyhydroxyazepane carboxamides and aminomethyl polyhydroxyazepanes, with potential pharmacological interest, are synthesized from diacetone d-mannose. Configurational assignments of the obtained products were determined.
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Development of chiral dinitrones as modular Lewis base catalysts: asymmetric ...
21 Jul 2010 at 1:50pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 20 July 2010
Young Seon, Oh , Shunsuke, Kotani , Masaharu, Sugiura , Makoto, Nakajima
Chiral dinitrones were synthesized by the condensation of a C2-symmetrical chiral dihydroxylamine with various aldehydes. The electronic and steric properties of the dinitrones can be modified by changing the aldehyde component. The activity of dinitrones as Lewis base catalysts was examined for the asymmetric allylation of aldehydes with allyltrichlorosilanes. Using DMPU as an additive in chloroform, the reaction proceeded at room temperature to afford allylated products in good yields and good enantioselectivities.
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Chirality transfer in mandelate ionic liquids through ion pairing effects
21 Jul 2010 at 1:50pm
Publication year: 2010
Source: Tetrahedron: Asymmetry, In Press, Corrected Proof, Available online 20 July 2010
Swetlana J., Sachnov , Karola, Schneiders , Peter S., Schulz , Peter, Wasserscheid
Ion pairing in [N-(3?-oxohexyl)-N-methylimidazolium][(R)-mandelate] was probed as a function of its concentration in ethanol and compared to the corresponding [(S)-camphorsulfonate] ionic liquid. The applied methodologies comprised asymmetric hydrogenation with ee monitoring as well as independent diffusion-ordered NMR and conductivity measurements.
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