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Sharpless Asymmetric Dihydroxylation (sharpless + asymmetric_dihydroxylation)
Selected AbstractsSharpless Asymmetric Dihydroxylation of Olefins in WaterSurfactant Media with Recycling of the Catalytic System by Membrane NanofiltrationADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2008Abstract This paper presents a new and more sustainable alternative approach for the Sharpless catalytic asymmetric dihydroxylation (AD) of olefins using a water/surfactant system as reaction media. The AD reaction was performed using several cationic and anionic surfactants allowing yields and enantiomeric excesses higher or comparable with the conventional systems (using organic mixtures). The use of this water/surfactant medium offers the additional advantage of performing the reactions without the need of a slow addition of olefins. Asymmetric dihydroxylation of 1-hexene in a 1.5,mM sodium cholate aqueous solution, using N -methylmorpholine N -oxide (NMO) as co-oxidant was selected as model system to evaluate the feasibility of recycling the Sharpless catalytic system by nanofiltration. The reaction media was processed by nanofiltration, the product was isolated in the permeate, whereas the catalytic system and surfactant were retained by the membrane and recycled through six successive reactions, improving the catalyst turn-over number. The experimental results were compared with the ones calculated on the basis of mass balances, membrane rejections to product and reaction yields. [source] Asymmetric Synthesis of Cyclic Hydroxy Ketones Derived from Enol Ethers via Sharpless Asymmetric Dihydroxylation.CHEMINFORM, Issue 9 2004A Study in the Correlation of the Enol Ether Chain Length, Enantioselectivity. Abstract For Abstract see ChemInform Abstract in Full Text. [source] On the Origin of the Facial Selectivity of the Sharpless Asymmetric Dihydroxylation of Styrene Derivatives.CHEMINFORM, Issue 26 2003Nicolas Moitessier Abstract For Abstract see ChemInform Abstract in Full Text. [source] An Efficient Total Synthesis of Decarestrictine D,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2008Priti Gupta Abstract An efficient total synthesis of decarestrictine D has been achieved using cross-metathesis or ring-closing metathesis and Yamaguchi macrolactonization as key steps. The stereogenic centres were generated by means of hydrolytic kinetic resolution (HKR) and Sharpless asymmetric dihydroxylation (AD). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Efficient Total Synthesis of (,)-(3S,6R)-3,6-Dihydroxy-10-methylundecanoic AcidEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2007Satyendra Kumar Pandey Abstract An efficient enantioselective synthesis of (,)-(3S,6R)-3,6-dihydroxy-10-methylundecanoic acid (1) from epichlorohydrin is described. The key steps include Jacobsen's HKR, Sharpless asymmetric dihydroxylation, regioselective opening of epoxide and cyclic sulfate. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Asymmetric Dihydroxylation of ,,,-Unsaturated Carboxylic Esterswith Trisubstituted C=C Bonds , Enantioselective Syntheses of Trisubstituted ,-ButyrolactonesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 9 2006Tobias Kapferer Abstract ,,,-Unsaturated esters with stereodefined trisubstitued C=C double bonds were prepared by the Arndt,Eistert homologation of ,,,-unsaturated carboxyl halides, by two-step methoxycarbonylation of allylbarium reagents, by deconjugation of ,,,-unsaturated esters, and by Horner,Wadsworth,Emmons variants of the Stobbe condensation. Sharpless asymmetric dihydroxylation of the ,,,-unsaturated esters, followed by spontaneous cyclization, afforded ,-hydroxy-,-lactones in moderate to good yields and with enantiomeric excesses of up to 97,%. Similarly, tetrahydroxy-,-lactones were obtained from diunsaturated esters; these lactones were converted into a bislactone and an unsaturated ,-hydroxy ,-lactone. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Total Synthesis of (+)-RutamarinADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2008Yi-Nan Zhang Abstract The first enantioselective total synthesis of (+)-rutamarin (1) is described. The synthetic route features the highly enantioselective construction of the stereogenic center via the Sharpless asymmetric dihydroxylation (99% ee), the facile assembly of quaternary carbon-centered 3-substituted side chain and high synthetic efficiency from readily available starting materials. Furthermore, the synthetic strategy could be readily adopted for the synthesis of (+)-rutamarin analogues. [source] A Facile Synthetic Method for the Preparation of s,-Symmetric (1, 2:4, 5)-Diepoxypentane Equivalent,CHINESE JOURNAL OF CHEMISTRY, Issue 7 2003Biao Jiang Abstract Optically active s,-symmetric (1, 2:4, 5)-diepoxypentane equivalent (10) has been synthesized in eight steps with moderate yields and diastereomeric excess by using Sharpless asymmetric dihydroxylation (AD reaction). Compound 10 can be used to prepare syn 1,3-diol subunit in natural product. [source] Enantioselective synthesis and antioxidant activity of 3-(3,4-dihydroxyphenyl)-glyceric acid,Basic monomeric moiety of a biologically active polyether from Symphytum asperum and S. caucasicumCHIRALITY, Issue 8 2010Maia Merlani Abstract The racemic and enantioselective synthesis of a novel glyceric acid derivative, namely, 2,3-dihydroxy-3-(3,4-dihydroxyphenyl)-propionic acid as well as the antioxidant activities is described. The virtually pure enantiomers, (+)-(2R,3S)-2,3-dihydroxy-3-(3,4-dihydroxyphenyl)-propionic acid and (,)-(2S,3R)-2,3-dihydroxy-3-(3,4-dihydroxyphenyl)-propionic acid were synthesized for the first time via Sharpless asymmetric dihydroxylation of trans-caffeic acid derivatives using the enantiocomplementary catalysts, (DHQD)2 -PHAL and (DHQ)2 -PHAL. The determination of enantiomeric purity of the novel chiral glyceric acid derivatives was performed by high-performance liquid chromatographic techniques on the stage of their alkylated precursors. The novel glyceric acid derivatives show strong antioxidant activity against hypochlorite and N,N -diphenyl- N -picryl-hydrazyl free radical. Their antioxidant activity is about 40-fold higher than that of the corresponding natural polyether and three-fold higher of trans-caffeic acid itself. Chirality, 2010. © 2010 Wiley-Liss, Inc. [source] | ||||||||||