- A general asymmetric synthesis of (R)-Matsutakeol and flavored analogs
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An efficient and practical synthetic route toward chiral matsutakeol and analogs was developed by asymmetric addition of terminal alkyne to aldehydes. (R)-matsutakeol and other flavored substances were feasibly synthesized from various alkylaldehydes in high yield (up to 49.5%, in three steps) and excellent enantiomeric excess (up to >99%). The protocols may serve as an alternative asymmetric synthetic method for active small-molecule library of natural fatty acid metabolites and analogs. These chiral allyl alcohols are prepared for food analysis and screening insect attractants.
- Liu, Jia,Li, Honglian,Zheng, Chao,Lu, Shichao,Guo, Xianru,Yin, Xinming,Na, Risong,Yu, Bin,Wang, Min
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- The substrate spectrum of the inverting sec-alkylsulfatase Pisa1
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The substrate spectrum of the inverting alkylsulfatase Pisa1 was investigated using a range of sec-alkyl sulfate esters bearing aromatic, olefinic and acetylenic moieties. Perfect enantioselectivities were obtained for substrates bearing groups of different size adjacent to the sulfate ester moiety. Insufficient selectivities could be doubled by using dimethyl sulfoxide (DMSO) as co-solvent. Hydrolytically unstable benzylic sulfate esters could be sufficiently stabilised by introduction of electron-withdrawing substituents. Overall, Pisa1 appears to be a very useful inverting alkylsulfatase for the deracemisation of rac-sec-alcohols via enzymatic hydrolysis of their corresponding sulfate esters, which furnishes homochiral products possessing the 'anti-Kazlauskas' configuration. Copyright
- Schober, Markus,Knaus, Tanja,Toesch, Michael,MacHeroux, Peter,Wagner, Ulrike,Faber, Kurt
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experimental part
p. 1737 - 1742
(2012/07/31)
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- Highly efficient kinetic resolution of allylic alcohols with terminal double bond
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In this study, the lipase-catalyzed kinetic resolution (Novozyme 435) was employed to prepare chiral allylic alcohols and acetates with terminal double bonds in enantiomeric excesses ranging from 94 to >99 %.
- Marques, Francisco A.,Oliveira, Marcos A.,Frensch, Gustavo,Sales Maia, Beatriz Helena L. N.,Barison, Andersson,Lenz, Cesar A.,Guerrero Jr., Palimecio G.
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p. 696 - 700
(2012/06/04)
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- Synthesis of α,α′-disubstituted linear ethers by an intermolecular nicholas reaction - Application to the synthesis of (+)-cis/-trans-lauthisan and (+)-cis/(+)-trans-obtusan
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A new and efficient methodology to prepare α,α'-disubstituted linear ethers through an intermolecular Nicholas reaction (interNR) is described. cis-2,8-Disubstituted oxocanes, cis-2,9-disubstituted oxonanes, their trans isomers, and their parent unsaturat
- Ortega, Nuria,Martin, Tomas,Martin, Victor S.
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scheme or table
p. 554 - 563
(2009/09/06)
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- Chemoenzymatic synthesis of optically active γ-alkyl-γ-butenolides
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rac-Hept-1-en-3-ol 4 was subjected to an enantioselective esterification in the presence of Novozyme 435 and vinyl crotonate as the acyl donor to give (3S)-oct-1-en-3-yl crotonate 7 in >99% ee and (3R)-alcohol 4 in 99% ee. The E-value of this enzymatic reaction was found to be >1000. The (S)-crotonic ester 7 was converted by ring-closing metathesis (RCM) using Grubbs' catalyst to give (S)-oct-2-en-4-olide 1 in 96% yield while keeping the high enantiomeric excess.
- Fujii, Mikio,Fukumura, Motonori,Hori, Yumiko,Hirai, Yasuaki,Akita, Hiroyuki,Nakamura, Kaoru,Toriizuka, Kazuo,Ida, Yoshiteru
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p. 2292 - 2298
(2007/10/03)
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- First synthesis of optically pure selenuranes and stereoselective alkaline hydrolysis. Their application to asymmetric [2,3] sigmatropic rearrangement of allylic selenoxides
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The first synthesis of optically pure selenuranes 1 has been accomplished by utilizing 2-exo-hydroxy-10 bornyl group as a chiral ligand Complete retention of the configuration has been observed in alkaline hydrolysis of 1 to give selenoxides 2. The structure of 1 and 2 has been fully established by X-ray crystallography. [2,3] Sigmatropic rearrangement of allylic selenoxides 2 gave the corresponding allylic alcohols 3 with up to 88% enantiomeric excess (ee). The [2,3] sigmatropic rearrangement of allylic selenoxides 2 progresses predominantly via an endo transition state.
- Kurose, Noriyuki,Takahashi, Tamiko,Koizumi, Toru
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p. 12115 - 12129
(2007/10/03)
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- Candida antarctica Lipase B Catalysed Kinetic Resolutions: Substrate Structure Requirements for the Preparation of Enantiomerically Enriched Secondary Alcanols
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The lipase B of the Candida antarctica yeast displays high enantioselectivity in transesterification reactions with chiral secondary alcohols in non-aqueous media.This was exploited to resolve a series of racemates structurally related to 2-octanol, namely 3-hydroxy-1-undecyne, 3-hydroxy-1-nonene, 3-nonanol, 1-chloro-2-octanol, 2-methyl-3-nonanol, 2,2-dimethyl-3-nonanol.The substrates were designed to probe the alcohol binding part of the active site of the lipase.The first four racemates could be resolved to produce compounds of high enantiomeric purity.A lipase catalysed transesterification of 1-chloro-2-octanol was observed. 2-Methyl-3-nonanol and 2,2-dimethyl-3-nonanol did not form any detectable amounts of product ester.The kinetic resolutions of the alcohols were performed with S-ethyl thiooctanoate as the acyl donor.
- Orrenius, Christian,Oehrner, Niklas,Rotticci, Didier,Mattson, Anders,Hult, Karl,Norin, Torbjoern
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p. 1217 - 1220
(2007/10/02)
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- A Tellurium Transposition Route to Allylic Alcohols: Overcoming Some Limitations of the Sharpless-Katsuki Asymmetric Epoxidation
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Good yields of enantiomeric allylic alcohols can be obtained in high enantiomeric excess (ee) by combining Sharpless-Katsuki asymmetric epoxidation process (SAE) with tellurium chemistry.The advantages of the tellurium process are as follows: (1) the 50percent yield limitation on the allylic alcohol in the Sharpless kinetic resolution (SKR) can be overcome; (2) allylic tertiary alcohols which are unsatisfactory substrates in the SKR can be obtained in high optical purity; (3) optically active secondary allylic alcohols with tertiary alkyl substituents (e.g. tert-butyl) at C-1 can be obtained in high ee; (4) optically active sterically congested cis secondary alcohols can be obtained in high ee; and (5) the nuisance of the slow SAE of some vinyl carbinols can be avoided.The key step in the reaction sequence is either a stereospecific 1,3-transposition of double bond and alcohol functionalities or an inversion of the alcohol configuration with concomitant deoxygenation of the epoxide function in epoxy alcohols.Trans secondary allylic alcohols can be converted to cis secondary allylic alcohols by way of erythro epoxy alcohols (glycidols); threo glycidyl derivatives are converted to trans secondary allylic alcohols.These transformations are accomplished by the action of telluride ion, generated in situ from the element, on a glycidyl sulfonate ester.Reduction of elemental Te is conveniently done with rongalite (HOCH2SO2Na) in an aqueous medium.This method is satisfactory when Te2- is required to attack at primary carbon site of a glycidyl sulfonate.In cases where Te2- is required to attack a secondary carbon site, reduction of the tellurium must be done with NaBH4 or LiEt3BH.Elemental tellurium is precipitated during the course of the reactions and can be recovered and reused.
- Dittmer, Donald C.,Discordia, Robert P.,Zhang, Yanzhi,Murphy, Christopher K.,Kumar, Archana,et al.
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p. 718 - 731
(2007/10/02)
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- A KINETIC RESOLUTION OF RACEMIC EPOXIDES BY A CHIRAL LITHIUM AMIDE
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A kinetic resolution of cis-disubstituted epoxides was effectively achieved by a chiral lithium amide, prepared from (S)-2-(pyrrolidin-1-yl)-methylpyrrolidine.
- Asami, Masatoshi,Kanemaki, Noriko
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p. 2125 - 2128
(2007/10/02)
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- ENANTIOSELECTIVE SYNTHESIS OF SEC-ALLYLALCOHOLS BY CATALYTIC ASYMMETRIC ADDITION OF DIVINYLZINC TO ALDEHYDES.
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Readily available chiral tridentate ligand 8 catalyzes the highly Si-face selective addition of diethyl-, di-n-propylzinc and, more significantly, of divinylzinc to aromatic and aliphatic aldehydes whereas bidentate ligands 11 and 12 exert a topologically reversed catalytic bias.
- Oppolzer, Wolfgang,Radinov, Rumen N.
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p. 5645 - 5648
(2007/10/02)
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- Catalytic Asymmetric Epoxidation and Kinetic Resolution: Modified Procedures Including in Situ Derivatization
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The use of 3A or 4A molecular sieves ( zeoiltes ) substantially increases the scope of the titanium(IV)-catalyzed asymmetric epoxidation of primary allylic alcohols.Whereas without molecular sieves epoxidations employing only 5 to 10 mol percent Ti(O-i-Pr)4 generally led to low conversion or low enantioselectivity, in the presence of molecular sieves such reactions generally led to high conversion (>95percent) and high enantioselectivity (90-95percent ee).The epoxidations of 20 primary allylic alcohols are described.Especially noteworthy are the epoxidations of cinnamyl alcohol, 2-tetradecyl-2-propen-1-ol, allyl alcohol, and crotyl alcohol-compounds which heretofore had been considered difficult substrates for asymmetric epoxidation.In the case of allylic alcohol, the use of cumene hydroperoxide substantially increases both the reaction rate and the conversion, even in the absence of molecular sieves.In general, enantioselectivities are slightly depressed (by 1-5percent ee) relative to reactions employing 50-100 mol percent Ti(O-i-Pr)4.The epoxidation of low molecular weight allylic alcohols is especially facilitated and, in conjuction with in situ derivatization, provides for the synthesis of many epoxy alcohol synthons which were previously difficult to obtain.The kinetic resolution of four secondary allylic alcohols with 10 mol percent Ti(O-i-Pr)4 is also described.The role of molecular sieves in the reaction and the effects of variation in reaction stoichiometry, oxidant, and tartrate are discussed.
- Gao, Yun,Hanson, Robert M.,Klunder, Janice M.,Ko, Soo Y.,Masamune, Hiroko,Sharpless, K. Barry
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p. 5765 - 5780
(2007/10/02)
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- ON THE PREPARATION OF OPTICALLY ACTIVE SECONDARY ALCOHOLS FROM A 1,3-DIOXAN-4-ONE: SUBSTITUTION WITH ORGANOCOPPER REAGENTS
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Organocopper reagents react with a chiral nonracemic 1,3-dioxan-4-one to afford substitution products with high diastereoselectivity.After treatment of the adducts with potassium t-butoxide, optically active secondary alcohols are obtained.
- Schreiber, Stuart L.,Reagan, Jeff
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p. 2945 - 2948
(2007/10/02)
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- ENANTIOSPECIFIC SYNTHESIS OF THE IMMUNOPOTENTIATORS erythro-9 (2-HYDROXY-3-NONYL) HYPOXANTHINES AND THE threo-DIASTEREOMERS.
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The title compounds were prepared enantiospecifically by kinetic resolution of (+/-) 1-nonene-3-ol via Sharpless oxidation.The products 1,2R-epoxy-nonane-3S-ol and 1-nonene-3R-ol were efficiently converted to all four stereoisomers of 2-hydroxy-3-nonylamine, which were subsequently incorporated into the target hypoxanthines to evaluate their immunopotentiating activity.
- Bessodes, M.,Abushanab, E.,Antonakis, K
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p. 5899 - 5902
(2007/10/02)
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