- An enantioselective approach to 2-alkyl substituted tetrahydroquinolines: Total synthesis of (+)-angustureine
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A simple and highly efficient synthetic approach to enantiopure 2-alkyl substituted tetrahydroquinoline 1 skeleton from aldehydes as starting materials and its application to the total synthesis of (+)-angustureine 2 is described. Key transformations incl
- Garg, Yuvraj,Gahalawat, Suraksha,Pandey, Satyendra Kumar
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p. 38846 - 38850
(2015/05/20)
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- Synthesis of the C(7)-C(22) Sector of (+)-Acutiphycin via O-directed double free radical alkyne hydrostannation with Ph3SnH/Et3B, double I-Sn exchange, and double stille coupling
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Herein a new double O-directed free radical hydrostannation reaction is reported on the structurally complex dialkyldiyne 11. Through our use of a conformation-restraining acetal to help prevent stereocenter-compromising 1,5-H-atom abstraction reactions b
- Hale, Karl J.,Maczka, Maciej,Kaur, Amarjit,Manaviazar, Soraya,Ostovar, Mehrnoosh,Grabski, Milosz
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p. 1168 - 1171
(2014/03/21)
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- Synthesis of substituted α,β-unsaturated δ-lactones from vinyl tellurides
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A new approach for the synthesis of α,β-unsaturated δ-lactones, a unit present in many natural products with interesting biological activities is described. The approach was based on the use of a vinyl telluride, and it is complementary to the methods usi
- Oliveira, Juliana M.,R. Freitas, Juliano C.,Comasseto, Jo?o Valdir,Menezes, Paulo Henrique
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experimental part
p. 3003 - 3009
(2011/04/27)
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- A route to 1,2-diols by enantioselective organocatalytic α-oxidation with molecular oxygen
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A route to 1,2-diols by the direct organocatalytic enantioselective α-oxidation of aldehydes using molecular oxygen is presented. Protected commercially available chiral pyrrolidines catalyze the asymmetric α-oxidation of aldehydes with singlet molecular oxygen with high enantioselectivity to furnish the corresponding diols after in situ reduction in high yield with up to 98% ee. Electrophilic singlet molecular oxygen was photo or chemically generated ('dark' 1O2).
- Ibrahem, Ismail,Zhao, Gui-Ling,Sundén, Henrik,Córdova, Armando
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p. 4659 - 4663
(2007/10/03)
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- Catalytic enantioselective hydrogenation of vinyl bis(boronates)
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Catalytic enantioselective hydrogenation of prochiral vinylmetallic reagents can provide an attractive alternative to hydrometalation and bismetalation of alkenes. In this contribution, the first highly enantioselective hydrogenation of vinyl boronic esters is described. The chiral reduction products are versatile intermediates for chemical synthesis. Copyright
- Morgan, Jeremy B.,Morken, James P.
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p. 15338 - 15339
(2007/10/03)
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- A highly diastereoselective synthesis of (1R)-(+)-camphor-based chiral allenes and their asymmetric hydroboration-oxidation reactions
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Synthesis of camphor derived chiral allenes and their hydroboration-oxidation reactions are described. Reaction of (1R)-(+)-camphor with alkynyllithium followed by the reduction of the resulted propargyl alcohol derivatives using AlH3 furnished chiral allenes 2a-g in excellent yields with high diastereoselectivity. Reduction of the propargyl alcohols with aluminum hydride proceeded through selective intermolecular anti-addition of hydride ion. The stereochemistry of the chiral allenes 2 was assigned based on lanthanide shift studies and chemical correlations. Diastereoselectivity was observed in the hydroboration-oxidation of 2 which produced a mixture of (E,R) and (E,S) stereoisomers in a ratio of 6:1 to 18:1.
- Hung, Shang-Cheng,Wen, Yen-Fang,Chang, Jia-Wen,Liao, Chun-Chen,Uang, Biing-Jiun
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p. 1308 - 1313
(2007/10/03)
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- Reaction of various oxiranes and carbon dioxide. Synthesis and aminolysis of five-membered cyclic carbonates
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Various oxiranes reacted with carbon dioxide at 100 °C using lithium bromide as a catalyst under atmospheric pressure to afford the corresponding five-membered cyclic carbonates quantitatively. The rate of the reaction increased as the bulkiness of substituents on the oxirane ring was reduced or an electron-withdrawing group was introduced on the oxirane ring. The stereochemistry of the reaction of oxirane and carbon dioxide was retention without loss of optical purity. When substituted phenylethylene carbonates were reacted with benzylamine, the selectivity to afford secondary alcohol increased as the electron-withdrawing ability of the para-substituent increased.
- Iwasaki, Takeshi,Kihara, Nobuhiro,Endo, Takeshi
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p. 713 - 719
(2007/10/03)
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- Asymmetric synthesis of (S)-Massoialactone
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An asymmetric synthesis of (S)-(+)-Massoialactone is described using the Sharpless asymmetric dihydroxylation and the regiospecific nucleophilic opening of a cyclic sulfate as key steps.
- Pais, Godwin C.G.,Fernandes, Rodney A.,Kumar, Pradeep
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p. 13445 - 13450
(2007/10/03)
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- Enantioselective hydrolysis of unbranched aliphatic 1,2-epoxides by Rhodotorula glutinis
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Epoxide hydrolase catalysed resolution of aliphatic terminal epoxides has been demonstrated for the hydrolysis of a homologous range of unbranched 1,2-epoxyalkanes by the yeast Rhodotorula glutinis. Both enantioselectivity and reaction rate were strongly influenced by the chain length of the epoxide used. Enantioselectivity showed an optimum in the hydrolysis of 1,2- epoxyhexane (E=84). Resolution of (±)-1,2-epoxyhexane resulted in (S)-1,2- epoxyhexane (e.e.>98%, yield=48%) and (R)-1,2-hexanediol (e.e.=83%, yield=47%).
- Weijers,Botes,Van Dyk,De Bont
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p. 467 - 473
(2007/10/03)
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- The asymmetric ene reaction of N-glyoxyloyl-(2R)-bornane-10,2-sultam with 1-pentene and 1-hexene
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The asymmetric ene reaction of N-glyoxyloyl-(2R)-bornane-10,2-sultam 2 and its hemiacetal 3 with 1-pentene 4 and 1-hexene 5 in the presence of Lewis acids is reported. All the ene reactions studied led to diastereoisomeric mixtures of olefins 6 and 7 or 8 and 9, with predominance of products of the (S) absolute configuration on the newly formed stereogenic center. The absolute configuration (via X-ray analysis of 6 and chemical correlation) and the extent of asymmetric induction were established. Stereochemical models are proposed.
- Jezewski, Artur,Chajewska, Katarzyna,Wielogorski, Zbigniew,Jurczak, Janusz
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p. 1741 - 1749
(2007/10/03)
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- Total syntheses of (+)-acutiphycin and (+)-trans-20,21-didehydroacutiphycin
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The first total syntheses of the cytotoxic macrolides (+)-acutiphycin (1) and (+)-trans-20,21-didehydroacutiphycin (2) have been achieved. An acyclic stereocontrol strategy was employed to establish the configurations at C(5), C(10), and C(13) as well as the E geometry of the C(8,9)-trisubstituted olefin. Importantly, the natural source of 1 and 2, the blue-green alga Osillatoria acutissima, no longer produces these metabolites.
- Smith III, Amos B.,Chen, Sean S.-Y.,Nelson, Frances C.,Reichert, Janice M.,Salvatore, Brian A.
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p. 10935 - 10946
(2007/10/03)
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- Lipase-Catalyzed Enantiomer Selective Hydrolysis of 1,2-Diol Diacetates
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Enantiomer selective hydrolysis of racemic 1,2-diol diacetates (rac-2a-h) was investigated by using the inexpensive commercial porcine pancreatic lipase.The hydrolysis proceeds with variable regioselectivity but with moderate to good enantioselectivity yielding a mixture of isomeric monoacetates (3a-h and 4a-h) and unchanged diacetate enantiomers (2a-h).Evidence was found that both monoacetates (3a-h and 4a-h) are formed with the same sense of enantiomer selectivity.
- Poppe, Laszlo,Novak, Lajos,Kajtar-Peredy, Maria,Szantay, Csaba
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p. 2211 - 2218
(2007/10/02)
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- Asymmetric Dihydroxylation of Olefins with a Simple Chiral Ligand
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A C2 symmetrical chiral ligand derived from (R,R)-trans-1,2-diaminocyclohexane is highly effective in the asymmetric cis-dihydroxylation of aromatic and aliphatic di- and trisubstituted olefins under stoichiometric conditions.
- Hanessian, Stephen,Meffre, Patrick,Girard, Mario,Beaudoin, Serge,Sanceau, Jean-Yves,Bennani, Youssef
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p. 1991 - 1993
(2007/10/02)
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- A CONVENIENT SYNTHESIS OF HOMOCHIRAL δ-ALKYLATED α,β-UNSATURATED δ-LACTONES
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The tert-butyl propiolate ion serves as a convenient and efficient nucleophile in boron trifluoride-catalyzed openings of homochiral, mono-substituted epoxides.The resulting tert-butyl 5-hydroxy-2-alkynoates are converted into the title compounds upon semihydrogenation followed by acid hydrolysis.Specific examples include the synthesis of parasorbic acid and massoilactone, two naturally derived lactones of the present type.The scope of the synthetic protocol is discussed.
- Hoeyer, Thomas,Kjaer, Anders,Lykkesfeldt, Jens
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p. 1042 - 1051
(2007/10/02)
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- Asymmetric Dihyroxylation of Alkenes with Osmium Tetroxide: Chiral N,N'-Dialkyl-2,2'-bipyrrolidine Complex
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Asymmetric osmylation of alkenes by using N,N'-dialkyl-2,2'-bipyrrolidines as the chiral ligands shows a high asymmetric induction and a marked dependence of the enantioselectivity on both the N-alkyl group and the reaction solvent.
- Hirama, Masahiro,Oishi, Tohru,Ito, Sho
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p. 665 - 666
(2007/10/02)
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- ASYMMETRIC OXIDATION OF OLEFINS TO VICINAL DIOLS WITH OSMIUM TETROXIDE
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High levels of asymmetry can be achieved in the osmium tetroxide cis-hydroxylation of olefins by employing (-)-(R,R)-N,N,N',N'-tetramethylcyclohexane-1,2-trans-diamine as a chiral ligand for the osmium.
- Tokles, Maritherese,Snyder, John K.
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p. 3951 - 3954
(2007/10/02)
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- AN ASYMMETRIC SYNTHESIS OF α-BENZYLOXY ALDEHYDES HAVING A CHIRAL TERTIARY CENTER - AN APPLICATION TO THE ASYMMETRIC SYNTHESIS OF exo-(+)-BREVICOMIN -
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α-benzyloxy aldehydes having a chiral tertiary center at α-carbon atom are synthesized in high enantiomeric excess by successive treatment of 2-methoxycarbonyl-3-phenyl-1,3-diazabicyclooctane with diisobutylaluminum hydride (DIBAL-H) and Grignard reagents.The asymmetric reaction is applied to the total synthesis of exo-(+)-brevicomin.
- Asami, Masatoshi,Mukaiyama, Teruaki
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- SYNTHESIS OF THE TWO ENANTIOMERIC FORMS OF 5-HEXADECANOLIDE PROPOSED PHEROMONE COMPONENT FROM VESPA ORIENTALIS
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The first synthesis of R-(+)-5-hexadecanolide 1 and of it's S isomer 2 has been achieved in 9 steps, from the C4 chiral synthon 3; the absolute configuration is determined by conversion of the key intermediates 12 and 13 into R-and S-1,2-heptandiol.
- Servi, Stefano
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p. 2023 - 2024
(2007/10/02)
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