- Nickel Hydride Catalyzed Cleavage of Allyl Ethers Induced by Isomerization
-
This report discloses the deallylation of O - and N -allyl functional groups by using a combination of a Ni-H precatalyst and excess Bronsted acid. Key steps are the isomerization of the O - or N -allyl group through Ni-catalyzed double-bond migration followed by Bronsted acid induced O/N-C bond hydrolysis. A variety of functional groups are tolerated in this protocol, highlighting its synthetic value.
- Kathe, Prasad M.,Berkefeld, Andreas,Fleischer, Ivana
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supporting information
p. 1629 - 1632
(2021/02/09)
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- Total Syntheses of C60- And C100-Dolichols
-
C60- and C100-dolichols were synthesized. A Z-selective Wittig reaction was achieved with high selectivity in a microflow system to realize the scalable supply of the Z-isoprene unit. An isoprene chain was efficiently elongated by an SN2-type coupling between allyl sulfone and allyl chloride using t-BuOK. These key reactions enabled the efficient syntheses of dolichols. This study will pave the way for the functional studies of dolichols.
- Hirao, Kohtaro,Ono, Risako,Manabe, Yoshiyuki,Masui, Seiji,Atomi, Haruyuki,Fukase, Koichi
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p. 11549 - 11559
(2020/10/12)
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- Asymmetric synthesis of γ-chiral borylalkanes: Via sequential reduction/hydroboration using a single copper catalyst
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The synthesis of γ-chiral borylalkanes through copper-catalyzed enantioselective SN2′-reduction of γ,γ-disubstituted allylic substrates and subsequent hydroboration was reported. A copper-DTBM-Segphos catalyst produced a range of γ-chiral alkylboronates from easily accessible allylic acetate or benzoate with high enantioselectivities up to 99% ee. Furthermore, selective organic transformations of the resulting γ-chiral alkylboronates generated the corresponding γ-chiral alcohol, arene and amine compounds.
- Han, Jung Tae,Lee, Jin Yong,Yun, Jaesook
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p. 8961 - 8965
(2020/11/23)
-
- Exploration of the Fluoride Reactivity of Aryltrifluoroborate on Selective Cleavage of Diphenylmethylsilyl Groups
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The first known report on the fluoride catalytic reactivity of potassium aryltrifluoroborate is described. The fluoride reactivity of phenyltrifluoroborate was controlled by substituents on the trifluoroborate-attached benzene, such as the methoxy group a
- Fujiki, Katsumasa,Tanaka, Katsunori
-
supporting information
p. 4616 - 4620
(2020/07/06)
-
- Method for synthesizing levorotatory citronellol by asymmetric hydrosilation of citral
-
The invention provides a method for synthesizing levorotatory citronellol from citral through asymmetric hydrosilation. The method comprises following steps: under the catalytic action of a chiral ruthenium complex, monohydrosilane is used as a hydrosilylation reagent, a Lewis acid is used as an auxiliary agent, and citral is subjected to asymmetric hydrosilylation to obtain levorotatory citronellol. According to the method, the ruthenium complex which is relatively low in price is used as the catalyst, meanwhile, the use amount of the ruthenium complex is effectively reduced, the maximum molar ratio of the chiral ruthenium complex to citral can reach 1: 30000, and the cost of the catalyst is remarkably reduced.
- -
-
Paragraph 0010; 0049-0065
(2020/04/17)
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- Enantioselective Synthesis and Activity of All Diastereoisomers of (E)-Phytal, a Pheromone Component of the Moroccan Locust, Dociostaurus maroccanus
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The Moroccan locust, Dociostaurus maroccanus (Thunberg, 1815) (Orthoptera: Acrididae), is a polyphagous pest capable of inflicting large losses in agriculture under favorable environmental and climatic conditions. Currently, control of the pest relies solely on the application of conventional insecticides that have negative effects on the environment and human safety. In the search for a more rational, environmentally acceptable approach for locust control, we have previously reported that (Z/E)-phytal (1) is a male-produced candidate sex pheromone of this acridid. This molecule, with two stereogenic centers at C-7 and C-11, has four different diastereomers along with the Z/E stereochemistry of the double bond at C-2. In this paper, we present for the first time the enantioselective synthesis of the four diastereomers of (E)-phytal and their electrophysiological and behavioral activity on males and females. Our results demonstrate that the (R,R)-phytal is the most active diastereomer in both assays, significantly attracting females in a double-choice Y olfactometer, and confirming the previous chromatographic assignment as component of the sex pheromone of the Moroccan locust.
- Guerrero, Angel,Ramos, Victoria Elena,López, Sergio,Alvarez, José María,Domínguez, Aroa,Coca-Abia, María Milagro,Bosch, María Pilar,Quero, Carmen
-
-
- Synthesis and Catalytic Activity of (3,4-Diphenylcyclopentadienone)Iron Tricarbonyl Compounds in Transfer Hydrogenations and Dehydrogenations
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Four (3,4-diphenylcyclopentadienone)iron tricarbonyl compounds were synthesized, and their activities in transfer hydrogenations of carbonyl compounds and transfer dehydrogenations of alcohols were explored and compared to those of the well-established [2,5-(SiMe3)2-3,4-(CH2)4(η4-C4C=O)]Fe(CO)3 (3). A new compound, [2,5-bis(3,5-dimethylphenyl)-3,4-diphenylcyclopentadienone]iron tricarbonyl (7), was the most active catalyst in both transfer hydrogenations and dehydrogenations, and compound 3 was the least active catalyst in transfer hydrogenations. Evidence was found for product inhibition of both 3 and 7 in a transfer dehydrogenation reaction, with the activity of 3 being more heavily affected. A monomeric iron hydride derived from 7 was spectroscopically observed during a transfer hydrogenation, and no diiron bridging hydrides were found under reductive or oxidative conditions. Initial results in the transfer hydrogenation of N-benzylideneaniline showed that 3 was a significantly less active catalyst in comparison to the (3,4-diphenylcyclopentadienone)iron tricarbonyl compounds.
- Funk, Timothy W.,Mahoney, Andrew R.,Sponenburg, Rebecca A.,Zimmerman, Kathryn P.,Kim, Daniel K.,Harrison, Emily E.
-
supporting information
p. 1133 - 1140
(2018/04/17)
-
- Pheromone synthesis. Part 258. Synthesis of the enantiomers of the beetle pheromones ethyl 4-methylheptanoate, 4-methyloctanoic acid and 4-methyl-1-nonanol, and HPLC analysis of their derivatives to determine their enantiomeric purities
-
The enantiomers of citronellal have been converted into the enantiomers of the following beetle pheromones: ethyl 4-methylheptanoate (produced by male Nicrophorus vespilloides), 4-methyloctanoic acid (produced by male Oryctes elegans), and 4-methyl-1-nonanol (produced by female Tenebrio molitor). The enantiomeric purities of the synthetic pheromones were determined by HPLC analysis of the corresponding acids after derivatization with Ohrui's reagent [(S)-1-(anthracene-2,3-dicarboximido)-2-propanol]. The enantiomers of 4-methyl-1-nonanol could also be analyzed employing another Ohrui's reagent [(1S,2S)-2-(naphthalene-2,3-dicarboximido)cyclohexane-1-carboxylic acid].
- Mori, Kenji,Akasaka, Kazuaki
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p. 182 - 187
(2018/10/16)
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- Method for preparing chiral citronellol through asymmetric catalytic hydrogenation of citral
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The invention relates to a method for preparing single chiral citronellol through asymmetric catalytic hydrogenation of E-type and/or Z-type citral in the technical field of chemical engineering. The method comprises the step of performing asymmetric hydrogenation on the E-type and/or Z-type citral to form single chiral citronellol under certain hydrogen pressure and at a certain temperature under the catalysis of a chiral rhodium complex. The reaction condition is mild, the method is convenient to operate, the reaction efficiency is higher, the product yield and the enantioselectivity can reach 99%, and the method has bright industrial application prospect.
- -
-
Paragraph 0047-0049
(2017/01/26)
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- Organoselenium and DMAP co-catalysis: Regioselective synthesis of medium-sized halolactones and bromooxepanes from unactivated alkenes
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A catalytic system consisting of bis(4-methoxyphenyl)selenide and 4-(dimethylamino)pyridine (DMAP) has been developed for the regioselective synthesis of medium-sized bromo/iodo lactones and bromooxepanes possessing high transannular strain. 77Se NMR, mass spectrometry and theoretical studies reveal that the reaction proceeds via a quaternary selenium intermediate.
- Verma, Ajay,Jana, Sadhan,Prasad, Ch. Durga,Yadav, Abhimanyu,Kumar, Sangit
-
supporting information
p. 4179 - 4182
(2016/03/19)
-
- Identification of 6-benzyloxysalicylates as a novel class of inhibitors of 15-lipoxygenase-1
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Lipoxygenases metabolize polyunsaturated fatty acids into signalling molecules such as leukotrienes and lipoxins. 15-lipoxygenase-1 (15-LOX-1) is an important mammalian lipoxygenase and plays a crucial regulatory role in several respiratory diseases such as asthma, COPD and chronic bronchitis. Novel potent and selective inhibitors of 15-LOX-1 are required to explore the role of this enzyme in drug discovery. In this study we describe structure activity relationships for 6-benzyloxysalicylates as inhibitors of human 15-LOX-1. Kinetic analysis suggests competitive inhibition and the binding model of these compounds can be rationalized using molecular modelling studies. The most potent derivative 37a shows a Ki value of 1.7 μM. These structure activity relationships provide a basis to design improved inhibitors and to explore 15-LOX-1 as a drug target.
- Eleftheriadis, Nikolaos,Thee, Stephanie,Te Biesebeek, Johan,Van Der Wouden, Petra,Baas, Bert-Jan,Dekker, Frank J.
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p. 265 - 275
(2015/03/30)
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- Pheromone synthesis. Part 256: Synthesis of the four stereoisomers of 5,11-dimethylpentacosane, a new sex pheromone component of the male Galleria mellonella (L.), with high stereochemical purities as determined by the derivatization-HPLC analysis of the eight stereoisomers of 5,11-dimethyl-8-pentacosanol
-
Abstract All the four stereoisomers of 5,11-dimethylpentacosane (>96.8% purity) were synthesized via the stereoisomers of 5,11-dimethyl-8-pentacosanol, whose stereoisomeric compositions could be determined precisely by their low temperature HPLC analysis after derivatization. 5,11-Dimethyl-8-pentacosanol was prepared by a Grignard reaction between 3-methylheptylmagnesium bromide and 4-methyloctadecanal, both of which were prepared from the commercially available enantiomers of citronellal (97-98% ee). Alternatively, (R)-3-methyl-1-heptanol could be prepared from methyl (R)-3-hydroxybutanoate (100% ee). Pd/C-catalyzed hydrogenation of a 5-methyl-1-alkene caused partial racemaization at C-5.
- Mori, Kenji,Akasaka, Kazuaki
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p. 4102 - 4115
(2015/06/02)
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- Enantioselectivity of the bioconversion of chiral citronellal during the inhibition of wheat seeds germination
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Citronellal is one of the most prominent monoterpenes present in many essential oils. Low persistence of essential oils as bioherbicides has often been addressed because of the high volatility of these compounds. Bioconversion of citronellal by wheat seeds releases less aggressive and injurious compounds as demonstrated by their diminished germination. We demonstrated that optically pure citronellal enantiomers were reduced to optically pure citronellol enantiomers with retention of the configuration both in isolated wheat embryos and endosperms. Our findings reveal the potential of essential oils as allelopathic agents providing an insight into their mechanism of action and persistence. Copyright
- Cavalieri, Andrea,Fischer, Ravit,Larkov, Olga,Dudai, Nativ
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p. 419 - 426
(2014/04/03)
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- Highly enantioselective hydrogenation of 2-substituted-2-alkenols catalysed by a ChenPhos-Rh complex
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Highly enantioselective hydrogenation of a variety of 2-substituted-2- alkenols has been achieved using a ChenPhos-Rh complex as catalyst, giving ≥99% ee for most substrates. Optically active antifungal agent amorolfine was first synthesised using hydrogenation as the key step. This journal is
- Wang, Quanjun,Liu, Xueying,Liu, Xian,Li, Bin,Nie, Huifang,Zhang, Shengyong,Chen, Weiping
-
supporting information
p. 978 - 980
(2014/01/06)
-
- COMPLEX CATALYSTS BASED ON AMINO-PHOSPHINE LIGANDS FOR HYDROGENATION AND DEHYDROGENATION PROCESSES
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The present application discloses novel PWNN and PWNWP metal catalysts for organic chemical syntheses including hydrogenation (reduction) of unsaturated compounds or dehydrogenation of substrates. The range of hydrogenation substrate compounds includes esters, lactones, enals, enones, enolates, oils and fats, resulting in alcohols, enols, diols, and triols as reaction products. The catalysts of current application can be used to catalyze a hydrogenation reaction under solvent free conditions. The present catalysts also allow the hydrogenation to proceed without added base, and it can be used in place of the conventional reduction methods employing hydrides of the main-group elements. Furthermore, the catalysts of the present application can catalyze a dehydrogenation reaction under homogenous and/or acceptorless conditions. As such, the catalysts provided herein can be useful in substantially reducing cost and improving the environmental profile of manufacturing processes for a variety of chemicals.
- -
-
Page/Page column 39; 40; 41; 42
(2014/09/29)
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- Biotransformations of terpenes by fungi from amazonian Citrus plants
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The biotransformations of (RS)-linalool (1), (S)-citronellal (2), and sabinene (3) with fungi isolated from the epicarp of fruits of Citrus genus of the Amazonian forest (i.e., C. limon, C. aurantifolia, C. aurantium, and C. paradisiaca) are reported. The
- Moreno Rueda, Maria Gabriela,Guerrini, Alessandra,Giovannini, Pier Paolo,Medici, Alessandro,Grandini, Alessandro,Sacchetti, Gianni,Pedrini, Paola
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p. 1909 - 1919
(2013/11/06)
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- A mild chemoselective Ru-catalyzed reduction of alkynes, ketones, and nitro compounds
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The chemoselective reduction of alkyne, ketones, or nitro groups using (Ph3P)3RuCl2 as an inexpensive catalyst and Zn/water as a stoichiometric reductant is reported. Depending on the nature of the additive and the temperature, good chemoselectivities were observed allowing, e.g., for the selective reduction of a nitro group in the presence of a ketone or an alkyne.
- Schabel, Tobias,Belger, Christian,Plietker, Bernd
-
supporting information
p. 2858 - 2861
(2013/07/19)
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- Synthesis of all the stereoisomers of 6-methyl-2-octadecanone, 14-methyl-2-octadecanone, and 6,14-dimethyl-2-octadecanone, sex pheromone components of the Lyclene dharma dharma moth, from the enantiomers of citronellal
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The enantiomers of citronellal were converted to all the stereoisomers of 6-methyl-2-octadecanone, 14-methyl-2-octadecanone, and 6,14-dimethyl-2- octadecanone, the female-produced sex pheromone components of the Lyclene dharma dharma moth. Three wellestablished procedures, the Wittig reaction, alkylation of alkynes, and acetoacetic ester synthesis, were employed for the carbon-carbon bond formation to connect the building blocks.
- Shikichi, Yasumasa,Mori, Kenji
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p. 1943 - 1951
(2013/01/15)
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- Ruthenium-catalyzed asymmetric transfer hydrogenation of allylic alcohols by an enantioselective isomerization/transfer hydrogenation mechanism
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Reducing hazards: A asymmetric transfer hydrogen reaction was developed to reduce prochiral allylic alcohols in high yield and excellent enantioselectivity (see example). Mechanistic studies indicate a novel enantioselective isomerization/transfer hydrogenation mechanism. This new reaction is much safer than high-pressure hydrogenation using H2 gas. Copyright
- Wu, Ruoqiu,Beauchamps, Marie G.,Laquidara, Joseph M.,Sowa Jr., John R.
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experimental part
p. 2106 - 2110
(2012/04/11)
-
- Liposomal circular dichroism. assignment of remote stereocenters in plakinic acids K and L from a plakortis-xestospongia sponge association
-
"Figure Presented" Two new ωtu-phenyl polyketide peroxides, plakinic acids K and L, were isolated from a two-sponge association of Plakortis halichondroides and Xestospongia deweerdtae. The absolute configurations of the remote dimethyl-branched stereocenters in plakinic acid K were assigned by degradation of plakinic acid K to a long-chain naphthamide and analysis by liposomal circular dichroism (L-CD) and comparison with synthetic standards.
- Dalisay, Doralyn S.,Quach, Tim,Molinski, Tadeusz F.
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supporting information; experimental part
p. 1524 - 1527
(2010/06/20)
-
- Synthesis of all the stereoisomers of 6-methyl-2-octadecanone, 6,14-dimethyl-2-octadecanone, and 14-methyl-2-octadecanone, the components of the female-produced sex pheromone of a moth, Lyclene dharma dharma
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All of the stereoisomers of the components of the female-produced sex pheromone of a moth, Lyclene dharma dharma, were synthesized. They are (R)- and (S)-6-methyl-2-octadecanone, (6R,14R)-, (6R,14S)-, (6S,14R)-, and (6S,14S)-6,14-dimethyl-2-octadecanone, and (R)- and (S)-14-methyl-2-octadecanone. Enantiomers of citronellal and methyl (S)-3-hydroxy-2-methylpropanoate were the starting materials, and olefin cross metathesis was employed as the key reaction.
- Mori, Kenji
-
scheme or table
p. 2798 - 2805
(2009/08/15)
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- Asymmetric transfer hydrogenation in aqueous media catalyzed by resin-supported peptide having a polyleucine tether
-
A resin-supported N-terminal prolyl peptide having a β-turn motif and a polyleucine tether has been developed for the organocatalytic asymmetric transfer hydrogenation under aqueous conditions. Polyleucine accelerated the reaction in a highly enantioselective manner by providing a hydrophobic microenvironment around the prolyl residue. The investigation of catalyst structures indicates that the l-form of polyleucine is essential for both reaction efficiency and enantioselectivity.
- Akagawa, Kengo,Akabane, Hajime,Sakamoto, Seiji,Kudo, Kazuaki
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scheme or table
p. 461 - 466
(2009/09/06)
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- Site-saturation mutagenesis of tryptophan 116 of saccharomyces pastorianus old yellow enzyme uncovers stereocomplementary variants
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Site-saturation mutagenesis was used to generate all possible replacements for Trp 116 of Saccharomyces pastorianus (formerly Saccharomyces carlsbergensis) old yellow enzyme (OYE). Our original hypothesissthat smaller amino acids at position 116 would allow better acceptance of bulky 3-alkylsubstituted 2-cyclohexenonessproved incorrect. Instead, Phe and Ile replacements favored the binding of some substrates in an opposite orientation, which yielded reversed stereochemical outcomes compared to that of the wild-type OYE. For example, W116I OYE reduced (R)- and (S)-carvone to enantiomeric products, rather than the diastereomers produced by the wild-type OYE. Deuterium labeling revealed that (S)-carvone reduction by the W116I OYE occurred by the same pathway as that by the wild type (net trans-addition of H2), proving that different substrate binding orientations were responsible for the divergent products. Trp 116 mutants also afforded different stereochemical outcomes for reductions of (R)- perillaldehyde and neral. Preliminary studies of an OYE family member whosenative sequence contains Ile at position 116 (Pichia stipitis OYE 2.6) revealed that this enzyme's stereoselectivity matched that of the wild-t ype S. pastorianus OYE, showing that the identity of the residue at position 116 does not solely determine the substrate binding orientation. Computational docking studies using an induced fit methodology successfully reproduced the majority of the experimental outcomes. These computational tools will allow preliminary in silico screening of additional residues to identify those most likely to control the substrate binding orientation and provide some guidance to future experimental studies.
- Padhi, Santosh Kumar,Bougioukou, Despina J.,Stewart, Jon D.
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experimental part
p. 3271 - 3280
(2009/07/30)
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- Synthesis of all the six components of the female-produced contact sex pheromone of the German cockroach, Blattella germanica (L.)
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All of the following six components of the female sex pheromone of the German cockroach, Blattella germanica (L.) were synthesized: (3S,11S)-3,11-dimethyl-2-nonacosanone (1), its 29-hydroxy derivative 2, its 29-oxo derivative 3, (3S,11S)-3,11-dimethyl-2-heptacosanone (4), its 27-hydroxy derivative 5, and its 27-oxo derivative 6. Both the enantiomers of citronellal were employed as the chiral sources and Wacker oxidation was employed for the introduction of the carbonyl group at C-2.
- Mori, Kenji
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p. 4060 - 4071
(2008/09/20)
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- Highly efficient asymmetric synthesis of fluvirucinine A1 via Zr-catalyzed asymmetric carboalumination of alkenes (ZACA)-lipase-catalyzed acetylation tandem process
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(Chemical Equation Presented) ZACA-lipase-catalyzed acetylation tandem process has been shown to proceed satisfactorily with either TBS-protected 4-penten-1-ol or 3-buten-1-ol to provide the corresponding enantiomerically pure (R)-2-ethyl-1-alkanols. Either (R)-5 or (R)-6 was converted to 3 in seven steps. The other fragment 4 was synthesized in nine steps from (-)-(S)-citronellol. Conversion of 3 and 4 into 99% pure fluvirucinine A 1 was achieved in four steps via amidation-ring closing metathesis, the overall yield in the longest linear sequence being 34% (13 steps).
- Liang, Bo,Negishi, Ei-Ichi
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p. 193 - 195
(2008/09/18)
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- Organocatalytic asymmetric transfer hydrogenation in aqueous media using resin-supported peptide having a polyleucine tether
-
A resin-supported N-terminal prolyl peptide having a β-turn motif and hydrophobic polyleucine chain effectively catalyzed the asymmetric transfer hydrogenation under aqueous conditions. The polyleucine tether provides a hydrophobic cavity in aqueous media that brought about a remarkable acceleration of the reaction. In addition, the polyleucine chain also turned out to be essential for high enantioselectivity.
- Akagawa, Kengo,Akabane, Hajime,Sakamoto, Seiji,Kudo, Kazuaki
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scheme or table
p. 2035 - 2037
(2009/04/18)
-
- Asymmetric bioreduction of C=C bonds using enoate reductases OPR1, OPR3 and YqjM: Enzyme-based stereocontrol
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Three cloned enoate reductases from the "old yellow enzyme" family of flavoproteins were investigated in the asymmetric bioreduction of activated alkenes. 12-Oxophytodienoate reductase isoenzymes OPR1 and OPR3 from Lycopersicon esculentum (tomato), and YqjM from Bacillus subtilis displayed a remarkably broad substrate spectrum by reducing α,β-unsaturated aldehydes, ketones, maleimides and nitroalkenes. The reaction proceeded with absolute chemoselectivity-only the conjugated C=C bond was reduced, while isolated olefins and carbonyl groups remained intact-with excellent stereoselectivities (ees up to >99%). Upon reduction of a nitroalkene, the stereochemical outcome could be determined via choice of the appropriate enzyme (OPR1 versus OPR3 or YqjM), which furnished the corresponding enantiomeric nitroalkanes in excellent ee. Molecular modelling suggests that this "enzyme-based stereocontrol" is caused by subtle differences within the active site geometries.
- Hall, Melanie,Stueckler, Clemens,Ehammer, Heidemarie,Pointner, Eva,Oberdorfer, Gustav,Gruber, Karl,Hauer, Bernard,Stuermer, Rainer,Kroutil, Wolfgang,Macheroux, Peter,Faber, Kurt
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experimental part
p. 411 - 418
(2009/04/10)
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- DIOPHEP, a chiral diastereoisomeric bisphosphine ligand: synthesis and applications in asymmetric hydrogenations
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Novel optically active diphosphine ligands, known as DIOPHEP, have been designed and synthesized starting from a derivative of tartaric acid. The ligands conjugate the sp3 chirality of the precursor of DIOP with the atropisomeric chirality of a biaryl scaffold. The stereorecognition abilities of DIOPHEP-Ru complex catalysts have been investigated in the asymmetric catalytic hydrogenation of some standard substrates suggesting a close relationship between dihedral angles and enantioselectivity.
- Cesarotti, Edoardo,Abbiati, Giorgio,Rossi, Elisabetta,Spalluto, Paola,Rimoldi, Isabella
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p. 1654 - 1659
(2008/12/22)
-
- Total synthesis of papulacandin D
-
A total synthesis of the antifungal agent papulacandin D is reported. The molecule is representative of a large class of C-aryl glycosides that exhibit significant antifungal activity. The synthetic strategy bifurcates the molecule into two nearly equal subunits, the arylglycoside and 18-carbon fatty acid side chain. The key strategic transformations are (1) the palladium catalyzed, organosilanolate-based cross-coupling of a protected glucal silanol and (2) a catalytic enantioselective allylation of a dienal using allyltrichlorosilane. The synthesis was accomplished in 31 steps overall from commercial starting materials to afford over 50 mg of the natural product. Copyright
- Denmark, Scott E.,Regens, Christopher S.,Kobayashi, Tetsuya
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p. 2774 - 2776
(2008/02/02)
-
- Asymmetric whole-cell bioreduction of an α,β-unsaturated aldehyde (citral): competing prim-alcohol dehydrogenase and C-C lyase activities
-
Asymmetric bioreduction of (E/Z)-3,7-dimethyl-2,6-octadienal (citral) using the enoate reductase activity of whole cells of yeasts, bacteria and fungi, gave the α,β-saturated aldehyde (R)-3,7-dimethyl-6-octenal (citronellal), which constitutes an important flavour component, in up to ≥95% ee. Depending on the microorganism, various amounts of prim-alcohols (nerol/geraniol and citronellol) were formed due to the action of competing prim-alcohol dehydrogenases. Citral lyase activity-leading to the loss of a C2-fragment (acetaldehyde) forming sulcatone-and oxidation of the aldehyde moiety yielding the carboxylic acid (geranic/neric acid) were detected as additional metabolic activities.
- Hall, Melanie,Hauer, Bernhard,Stuermer, Rainer,Kroutil, Wolfgang,Faber, Kurt
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p. 3058 - 3062
(2007/10/03)
-
- Synthesis of the four stereoisomers of 7-acetoxy-15-methylnonacosane, a component of the female sex pheromone of the screwworm fly, Cochliomyia hominivorax
-
The four stereoisomers of 7-acetoxy-15-methylnonacosane (1), a component of the female sex pheromone of the New World screwworm fly (Cochliomyia hominivorax) were synthesized. The stereogenic center at C-15 of 1 originated from that of the enantiomers of citronellal, and that at C-7 was generated by lipase-catalyzed asymmetric acetylation of (3RS,11R)- and (3RS,11S)-17-methyl-1- trimethylsilylpentacos-1-yn-3-ol (13). Three of the stereoisomers of 1 showed equivalent good pheromone activity, while the activity of (7R,15R)-1 was weak.
- Mori, Kenji,Ohtaki, Takashi,Ohrui, Hiroshi,Berkebile, Dennis R.,Carlson, David A.
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p. 1768 - 1778
(2007/10/03)
-
- Allyl, methallyl, prenyl, and methylprenyl ethers as protected alcohols: Their selective cleavage with diphenyldisulfone under neutral conditions
-
Diphenyldisulfone is a mild and efficient reagent for selective cleavage of methylprenyl (2,3-dimethylbut-2-en-1-yl), prenyl (3-methylbut-2-en1-yl), and methallyl (2-methylallyl) ethers. These reaction conditions are compatible with the presence of other protecting groups such as acetals, acetates, and allyl, benzyl, and TBDMS ethers. Exposure of 2,3-dimethylbut-2-en-1-yl and 3-methylbut-2-en1-yl ethers to diphenyldisulfone led to the formation of 2,3-dimethylbuta-1,3-diene and isoprene, respectively. 2-Methylallyl ethers undergo isomerization to 2-methylpropenyl ethers, which are easily hydrolyzed into the corresponding free alcohols and isobutyraldehyde.
- Markovic, Dean,Vogel, Pierre
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p. 2693 - 2696
(2007/10/03)
-
- Synthesis of the 1,5-dimethylic chiron enantiomers, 3,7,11-trimethyldodec-10-en-1-ol: Application to enantiomeric syntheses of tribolure and a marine fatty acid
-
A convenient synthesis of the title chiron antipodes has been developed starting from (±)-citronellol via a sequential acetylation protocol using two lipases. The different stereoisomers of the chiron were then functionalized by simple routes to (4R,8R)-dimethyldecanal, an insect pheromone and (5R,9R)-5,9,13-trimethyltetradecanoic acid, a marine phospholipid fatty acid.
- Sankaranarayanan,Sharma, Anubha,Chattopadhyay, Subrata
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p. 1373 - 1378
(2007/10/03)
-
- Indium-mediated chemoselective deprotection of trichloroethoxycarbonyl and trichloroacetyl groups
-
A new, mild, and chemoselective method for the deprotection of trichloroethoxylcarbonyl and trichloroacetyl groups is described.
- Valluri, Muralikrishna,Mineno, Tomoko,Hindupur, Rama M.,Avery, Mitchell A.
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p. 7153 - 7154
(2007/10/03)
-
- Synthesis of the spiroacetal parts of spirofungin A and B
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The C9-C20 spiroacetal parts of spirofungin A and B, antifungal antibiotics from Streptomyces violaceusniger Tu 4113, were synthesized simultaneously from (S)-citronellyl bromide and (±)-epoxy alcohol via alkyne-lactone coupling reaction and diastereomeric separation. (C) 2000 Elsevier Science Ltd.
- Shimizu, Yuko,Kiyota, Hiromasa,Oritani, Takayuki
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p. 3141 - 3144
(2007/10/03)
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- Syntheses of optically active citronellol, citronellal, and citronellic acid by microbial oxidation and double coupling system in an interface bioreactor
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We have already reported that (RS)-Citronellol [(RS)-1] can be optically resolved via a transacetylation with acetyl coenzyme A [acetyl-CoA] by the aid of alcohol acetyltransferase [AATFase] in Pichia kluyveri IFO 1165, which we have referred to as a double coupling system (E value, 30 to 40). In this system, although (R)-1 is obtained at over 98% ee, (S)-Citronellyl acetate [(S)-2] is prepared at 70 to 80% ee. In this article, we report on the conversion of (R)-1 to (R)-Citronellal [(R)-3] and (R)-Citronellic acid [(R)-4] in high yield without racemization by the aid of Rhodococcus equi JCM 6817 and Geotrichum candidum JCM 01747, respectively. On the other hand, the low ee of (S)-1 (78% ee) prepared via the alkaline hydrolysis of (S)-2 is converted to optically active (S)-1 and (S)-4 in high yield with a repeated double coupling system with P. kluyveri IFO 1165 and via enantioselective oxidation with Candida viswanathii IFO 10321, respectively. Thus, five optically active terpenoids related to citronellol, except for (S)-3, were efficiently synthesized via microbial transformations in an interface bioreactor.
- Oda, Shinobu,Sugai, Takeshi,Ohta, Hiromichi
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p. 2819 - 2823
(2007/10/03)
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- 2,2',5,5'-tetramethyl-4,4'-bis(diphenylphoshino)-3,3'-bithiophene: A new, very efficient, easily accessible, chiral biheteroaromatic ligand for homogeneous stereoselective catalysis
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The four-step straightforward synthesis of enantiopure (+)- and (-)- 2,2',5,5'-tetramethyl-4,4'-bis(diphenylphoshino)-3,3'-bithiophene (tetraMe- BITIOP), anew C2-symmetry chelating ligand for transition metals, is described, starting from 2,5-dimethylthiophene. The complexes of this electron-rich diphosphine with Ru(II) and Rh(I) were used as catalysts in some homogeneous hydrogenation reactions of prostereogenic carbonyl functions of α- and β-ketoesters, of prostereogenic carbon-carbon double bonds of substituted acrylic acids, and of N-acetylenamino acids. The enantiomeric excesses were found to be excellent in all the experiments and comparable with the best results reported in the literature for the same reactions, carried out under similar experimental conditions, with the metal complexes of the most popular chiral diphosphine ligands as catalysts.
- Benincori, Tiziana,Cesarotti, Edoardo,Piccolo, Oreste,Sannicolo, Franco
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p. 2043 - 2047
(2007/10/03)
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- Application of [Ru((R)-BINAP)(MeCN)(1-3:5,6-η-C8H11)](BF4) as a catalyst precursor for enantioselective hydrogenations
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A catalyst system employing [Ru((R)-BINAP)(MeCN)(1-3:5,6-η- C8H11)](BF4) as catalyst precursor was evaluated using the enantioselective hydrogenations of tiglic acid, α-acetamidocinnamic acid, itaconic acid, methyl tiglate, dimethyl itaconate, geraniol, ethyl acetoacetate, and dimethyl oxaloacetate as a series of typical substrates. Acetone and MeOH were used as model aprotic and protic solvents, respectively. The hydrogenation of substrates containing an α,β-unsaturated carboxylic acid functionality required stoichiometric quantities of NEt3 to occur at reasonable rates in acetone solution, while in MeOH solution it did not. The enantioselectivities were typically higher in acetone than in MeOH. This catalyst system is among the more enantioselective ruthenium-BINAP type systems reported for the catalytic hydrogenation of substrates containing an α,β-unsaturated acid or ester functionality. The enantioselectivities for the hydrogenation of ketones ranged from poor (15%) to moderate (74%). 1,4- Dicarboxylate substrates with the prochiral olefin or ketone at the 2- position were all hydrogenated in good to high ee with the same enantioface selectivity both with our system and other catalysts reported in the literature. This raised the possibility that these substrates were hydrogenated through intermediates with similar structural features.
- Daley, Christopher J.A.,Wiles, Jason A.,Bergens, Steven H.
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p. 1447 - 1456
(2007/10/03)
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- Kinetic influences on enantioselectivity in asymmetric catalytic hydrogenation
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The influence of reaction conditions on enantioselectivity in the RuII-(binap)-catalyzed asymmetric hydrogenation of allylic alcohols is discussed. This work highlights the importance of considering kinetic influences in addition to the stereochemical aspects of the chiral catalytic environment in interpreting catalytic behavior in asymmetric hydrogenation reactions.
- Sun, Yongkui,Wang, Jian,LeBlond, Carl,Reamer, Robert A.,Laquidara, Joseph,Sowa Jr., John R.,Blackmond, Donna G.
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- Complete relative stereochemistry of maitotoxin
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By addressing the relative stereochemistry of the four acyclic portions via organic synthesis, the complete relative stereochemistry of maitotoxin (MTX) has been established as 1B. The relative stereochemistry of the C.1-C.15 portion was elucidated via a two-phase approach: (1) the synthesis of the eight diastereomers possible for model C, representing the C.1-C.11 portion, and the eight diastereomers possible for model D, representing the C.11-C.15 portion, and the comparison of their proton and carbon NMR characteristics with those of MTX, concluding that 9 and 35 represent the relative stereochemistry of the corresponding portions of MTX; (2) the synthesis of the two remote diastereomers 51 and 52, and comparison of their proton and carbon NMR characteristics with those of MTX, concluding that 51 represents the relative stereochemistry of the C.1-C.15 portion of MTX. The relative stereochemistry of the C.35-C.39, C.63-C.68, and C.134-C.142 acyclic portions was established via (1) the synthesis of the 8, 8, and 16 diastereomers possible for models E, F, and G, respectively, and (2) the comparison of their proton and carbon NMR characteristics with those of MTX, concluding that 81, 117, and 187, respectively, represent the relative stereochemistry of the corresponding portions of MTX. Some biogenetic considerations have been given to speculate on the absolute configuration of MTX. The vicinal proton coupling constants observed for models 51, 81, 117, and 187 were used to elucidate their preferred solution conformation. Assembling the preferred solution conformations found for the four acyclic portions allows one to suggest that the approximate global conformation of MTX is represented by the shape of a hook, with the C.35-C.39 portion being its curvature. MTX appears to be conformationally relatively rigid, except for conformational flexibility around the C.7-C.9 and C.12-C.14 portions. On the basis of the experimental results gained in the current work, coupled with those in the AAL-toxin/fumonisin area, it has been pointed out that the structural properties of 51, 81, 117, 187 and their diastereomers are inherent to the specific stereochemical arrangement of the small substituents on the carbon backbone and are independent from the rest of the molecule. Thus, it has been suggested that each of these diastereomers has the capacity to install a unique structural characteristic through a specific stereochemical arrangement of substituents on the carbon backbone, and that fatty acids and related classes of compounds may be able to carry specific information and serve as functional materials in addition to structural materials.
- Zheng,DeMattei,Wu,Duan,Cook,Oinuma,Kishi
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p. 7946 - 7968
(2007/10/03)
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- New Class of Chiral Diphosphine Ligands for Highly Efficient Transition Metal-Catalyzed Stereoselective Reactions: The Bis(diphenylphosphino) Five-membered Biheteroaryls
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The synthesis and application of three examples of a new class of chiral (C2) atropisomeric diphosphines characterized by two interconnected five-membered heteroaromatic rings, with hindered rotation around the interanular bond, are described.Optically pure (+)- and (-)-2,2'-bis(diphenylphosphino)-4,4',6,6'-tetramethyl-3,3'-bibenzothiophene (tetraMe-bitianp) (1a) and the parent unsubstituted system (+)- and (-)-bitianp (1b) were synthesized.They were found to be optically stable at 100 deg C and were successfully employed as ligands in the Ru(II)-catalyzed hydrogenation of α- and β-oxo esters to the corresponding α- and β-hydroxy esters and in the hydrogenation of olefinic substrates.The optical and chemical yields were comparable with those reported for the same Ru(II)-binap-catalyzed reactions carried out under the same experimental conditions.The 2,2'-bis(diphenylphosphino)-3,3'-bibenzofuran (1c), the oxygenated analogue of bitianp, was found to be configurationally unstable at room temperature.Complete structural X-ray elucidation of the Pd complexes of 1a-c is reported.The advantages of these biheteroaromatic ligands over the classical biaryl systems are discussed.
- Benincori, Tiziana,Brenna, Elisabetta,Sannicolo, Franco,Trimarco, Licia,Antognazza, Patrizia,et al.
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p. 6244 - 6251
(2007/10/03)
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- A re-examination of pressure effects on enantioselectivity in asymmetric catalytic hydrogenation
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Marked shifts in enantioselectivity in the asymmetric hydrogenation of several prochiral substrates were observed as a function of the availability of hydrogen to the catalyst in both heterogeneous and homogeneous catalytic reactions. The key kinetic parameter affecting enantioselectivity was found to be concentration of molecular hydrogen in the liquid phase, [H2], rather than hydrogen pressure in the gas phase, and it was observed that under typical reaction conditions, [H2] could differ widely from its equilibrium saturation value. It was demonstrated that the reported pressure dependence on enantioselectivity may in fact be reproduced at constant pressure for several systems by varying the rate of gas-liquid mass transfer. The general significance of the conclusions suggest that considerations of hydrogen diffusion limitations might be important in other asymmetric hydrogenation studies reported in the literature. For systems where enantioselectivity depends positively on hydrogen pressure, the intrinsic ability of a catalyst to effect asymmetric hydrogenation may be masked in a reaction carried out under conditions where gas-liquid diffusion is the rate-limiting step.
- Sun,Landau,Wang,LeBlond,Blackmond
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p. 1348 - 1353
(2007/10/03)
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- Catalytic synthesis of (R) and (S) citronellol by homogeneous hydrogenation over amidophosphinephosphinite and diaminodiphosphine rhodium complexes
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The enantioselective production of citronellol (ee = 84% R and 80% S) is performed by hydrogenation of geraniol 1 and nerol 2 over cationic rhodium complexes modified by amidophosphinephosphinite and diaminodiphosphine chiral ligands.
- Ali,Allaoud,Karim,Roucoux,Mortreux
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p. 369 - 370
(2007/10/02)
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- Cationic BINAP-Ru(II) Halide Complexes: Highly Efficient Catalysts for Stereoselective Asymmetric Hydrogenation of α- and β-Functionalized Ketones
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Cationic ruthenium-BINAP complexes 5, 7, and 10 of the formula Y, where X = Cl, Br, I; Y = Cl, Br, I, BF4, B(C6H5)4; arene = benzene, p-cymene, ethyl benzoate, and their enantiomers have been prepared by the reaction of arene-ruthenium halide complexes 4, 6, and 9 with (S)-BINAP or (R)-BINAP.Structures of the complexes were established by spectroscopy, conductivity, and a single-crystal X-ray analysis (5d: orthorhombic, P21212; a=20.141(2) Angstroem, b=18.504(1) Angstroem, c=12.241(1) Angstroem, V=4562.0(7) Angstroem3, Z=4, R=0.078 for unique 4177 reflections).BINAP derivatives with various substituents at the para and meta positions of four phenyl rings on phosphorus atoms and their cationic Ru(II) complexes have also been synthesized.These BINAP-Ru(II) complexes have been used as catalysts for the asymmetric hydrogenation of various unsaturated organic compounds such as α- and β-keto esters, allylic alcohols, and α,β-unsaturated carboxylic acids in excellent diastereo- and/or enantioselectivities.Catalytic activities and stereoselectivities depend highly on reaction conditions such as solvent, temperature, and additives.Variation of halogen ligands bound to ruthenium atom and substituents on four phenyl rings of BINAP also have exerted remarkable effects on the efficiency of the catalysis.Asymmetric hydrogenation of methyl (+/-)-2-(benzamidomethyl)-3-oxobutanoate catalyzed by the species derived from 9c and 3,5-(t-Bu)2-BINAP afforded the corresponding syn-(2S,3R)-17 in 98percent de and 99percent ee.
- Mashima, Kazushi,Kusano, Koh-hei,Sato, Naomasa,Matsumura, Yoh-ichi,Nozaki, Kyoko,et al.
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p. 3064 - 3076
(2007/10/02)
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- BAKER'S YEAST MEDIATED SYNTHESIS OF (5SR,9S)-5,9-DIMETHYL-HEPTADECANE AND (5SR,9S)-5,9-DIMETHYL-PENTADECANE; THE MAIN SEX-PHEROMONE COMPONENTS OF Leucoptera scitella AND Perileucoptera coffeella ENRICHED IN 9S-ISOMERS
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A mixture of (5S,9S)-5,9-dimethyl-heptadecane (1a), the main sex-pheromone component of leucoptera scitella, and its (5R,9S)-isomer (2a) was synthesized conveniently from (R)-citronellal (4, obtained from racemic citronellal by enantiomer selective baker's yeast reduction) in four steps. (5SR,9S)-5,9-Dimethyl-pentadecane (mixture of 1b and 2b), a possible sex-attractant of Perileucoptera coffeella was prepared analogously.
- Poppe, L.,Novak, L.,Devenyi, J.,Szantay, Cs.
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p. 2643 - 2646
(2007/10/02)
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- Catalytic asymmetric hydrogen migration of allylamines
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This review describes some preparative aspects and practical applications of BINAP-Rh(I) catalyzed enantioselective isomerization of prochiral allylamines recently developed through the joint effort of several groups in Japan. In addition, the novel, sophisticated reaction mechanisms are discussed.
- Otsuka,Tani
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p. 665 - 680
(2007/10/02)
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- New efficient methods for the synthesis and in-situ preparation of ruthenium(II) complexes of atropisomeric diphosphines and their application in asymmetric catalytic hydrogenations
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A new synthetically useful method for the synthesis of the diphosphine ruthenium dicarboxylato complexes (P-P)Ru(O2CR)2(R= CF3 and CH3) is presented, which uses the easily accessible complex (COD)2Ru2(μ-O2CCF3)4 as starting material. This complex as well as (COD)(Ru(ηO2CCH3)2 and (COD)2Ru2Cl4(NCCH3) have been shown to be suitable precursor complexes for the in-situ preparation of ruthenium(II) dicarboxylato and dichloro complexes of atropisomeric diphosphines, respectively. The high efficacy of the preformed and in-situ generated ruthenium complexes as precatalysts is demonstrated in asymmetric hydrogenations of allylic alcohols, enamides, and a β-keto ester.
- Heiser,Broger,Crameri
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- Asymmetric Conjugate Addition to Unsaturated Chiral Amido Alcohols Using Grignard Reagents Co-ordinated with Tertiary Amines or DBU. Preparation of Optically Active 3-Substituted Carboxylic Acids and (S)-(-)-Citronellol
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Optically active 3-substituted carboxylic acids and (S)-(-)-citronellol have been obtained by diastereoselective conjugate addition of Grignard reagents co-ordinated with 1,8-diazabicyclo-undec-7-ene (DBU) to chiral amidoalcohols derived from (S)-proline.
- Soai, Kenso,Machida, Hideaki,Yokota, Noriko
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p. 1909 - 1914
(2007/10/02)
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