- A practical enantioselective synthesis of massoialactone via hydrolytic kinetic resolution
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An efficient enantioselective synthesis of (R)- and (S)-massoialactone has been achieved. The key steps are the hydrolytic kinetic resolution of a racemic epoxyheptane with (R,R)-(salen)-CoIIIOAc complex and ring-closing metathesis of homoallylic alcohol derived acrylate esters using Grubb's catalyst.
- Gupta, Priti,Naidu, S. Vasudeva,Kumar, Pradeep
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Read Online
- A mononuclear manganese complex of a tetradentate nitrogen ligand - Synthesis, characterizations, and application in the asymmetric epoxidation of olefins
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A new chiral manganese complex (C1) bearing a tetradentate nitrogen ligand containing chiral bipyrrolidine and benzimidazole moieties was prepared. The structure of C1 was confirmed by ESI-MS and crystallography. This manganese complex is an active catalyst for the asymmetric epoxidation of various olefins with excellent conversion (up to 99%) and high enantiomeric excess (up to 96%ee) with hydrogen peroxide as the oxidant in the presence of 2-ethylhexanoic acid or acetic acid. Compared with previous structurally similar manganese complexes with different diamine backbones (C2, cyclohexanediamine; C3, diamine from L-proline), C1 showed improved asymmetric induction, especially for simple olefins such as styrene derivatives and substituted chromene. The possible reasons for the improvement of the ee values are discussed in the text on the basis of the crystal structures of the manganese complexes.
- Shen, Duyi,Miao, Chengxia,Wang, Shoufeng,Xia, Chungu,Sun, Wei
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- Total synthesis of natural (?)- and unnatural (+)-Melearoride A
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This communication details the first total synthesis of the 13-membered macrolide, (?)-Melearoride A, as well as unnatural (+)-Melearoride A. The synthesis features a concise 13 step synthesis (11 steps longest linear sequence) that offers flexible stereo-control and multiple opportunities for unnatural analog synthesis to delve into antifungal SAR. The route features a cuprate addition, an Evans asymmetric alkylation, and a ring-closing metathesis (RCM) to close the 13-membered macrocyclic core.
- Reed, Carson W.,Fulton, Mark G.,Nance, Kellie D.,Lindsley, Craig W.
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supporting information
p. 743 - 745
(2019/02/09)
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- Photocatalytic Asymmetric Epoxidation of Terminal Olefins Using Water as an Oxygen Source in the Presence of a Mononuclear Non-Heme Chiral Manganese Complex
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Photocatalytic enantioselective epoxidation of terminal olefins using a mononuclear non-heme chiral manganese catalyst, [(R,R-BQCN)MnII]2+, and water as an oxygen source yields epoxides with relatively high enantioselectivities (e.g., up to 60% enantiomeric excess). A synthetic mononuclear non-heme chiral Mn(IV)-oxo complex, [(R,R-BQCN)MnIV(O)]2+, affords similar enantioselectivities in the epoxidation of terminal olefins under stoichiometric reaction conditions. Mechanistic details of each individual step of the photoinduced catalysis, including formation of the Mn(IV)-oxo intermediate, are discussed on the basis of combined results of laser flash photolysis and other spectroscopic methods.
- Shen, Duyi,Saracini, Claudio,Lee, Yong-Min,Sun, Wei,Fukuzumi, Shunichi,Nam, Wonwoo
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supporting information
p. 15857 - 15860
(2016/12/23)
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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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- Bioproduction of chiral epoxyalkanes using styrene monooxygenase from rhodococcus sp. ST-10 (RhSMO)
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We describe the enantioselective epoxidation of straight-chain aliphatic alkenes using a biocatalytic system containing styrene monooxygenase from Rhodococcus sp. ST-10 and alcohol dehydrogenase from Leifsonia sp. S749. The biocatalyzed enantiomeric epoxidation of 1-hexene to (S)-1,2-epoxyhexane (44.6 mM) using 2-propanol as the hydrogen donor was achieved under optimized conditions. The biocatalyst had broad substrate specificity for various aliphatic alkenes, including terminal, internal, unfunctionalized, and di- and tri-substituted alkenes. Here, we demonstrate that this biocatalytic system is suitable for the efficient production of enantioenriched (S)-epoxyalkanes.
- Toda, Hiroshi,Imae, Ryouta,Itoh, Nobuya
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p. 3443 - 3450
(2015/02/05)
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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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p. 3003 - 3009
(2011/04/27)
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- Total synthesis of berkelic acid
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A productive total synthesis of both enantiomers of berkelic acid (1) is outlined that takes the structure revision of this bioactive fungal metabolite previously proposed by our group into account. The successful route relies on a fully optimized triple-deprotection/1,4-addition/spiroacetalization cascade reaction sequence, which delivers the tetracyclic core 32 of the target as a single isomer in excellent yield. The required cyclization precursor 31 is assembled from the polysubstituted benzaldehyde derivative 20 and methyl ketone 25 by an aldol condensation, in which the acetyl residue in 20 transforms from a passive protecting group into an active participant. Access to fragment 25 takes advantage of the Collum-Godenschwager variant of the ester enolate Claisen rearrangement, which clearly surpasses the classical Ireland-Claisen procedure in terms of diastereoselectivity. Although it is possible to elaborate 32 into the target without any additional manipulations of protecting groups, a short detour consisting in the conversion of the phenolic -OH into the corresponding TBS-ether is beneficial. It tempers the sensitivity of the compound toward oxidation and hence improves the efficiency and reliability of the final stages. Orthogonal ester groups for the benzoate and the aliphatic carboxylate terminus of the side chain secure an efficient liberation of free berkelic acid in the final step of the route. Queue up: Three deprotection and three bond-forming reactions, all of which are effected just by a trace of HCl, zip an easily attained enone to the polycyclic core of berkelic acid in diastereomerically pure form and essentially quantitative yield. This cascade process paves the way to a concise and effective total synthesis of this alleged metalloproteinase-3 inhibitor and cytotoxic metabolite derived from an extremophilic fungus.
- Snaddon, Thomas N.,Buchgraber, Philipp,Schulthoff, Saskia,Wirtz, Conny,Mynott, Richard,Fuerstner, Alois
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supporting information; experimental part
p. 12133 - 12140
(2011/02/25)
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- Development of a concise and general enantioselective approach to 255-disubstituted-3-hydroxytetrahydrofurans
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Concise syntheses of 2,5-disubstituted-3-hydroxytetrahydrofurans have been developed that provide access to each configurational isomer of this scaffold from a single aldol adduct. Application of these methods to the rapid preparation of (6S,7S,9S,1QS)- a
- Kang, Baldip,Mowat, Jeffrey,Pinter, Thomas,Britton, Robert
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supporting information; experimental part
p. 1717 - 1720
(2009/09/06)
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- Synthesis of (-)-berkelic acid
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An extremophilic challenge: Stereospecific condensation of a fully functionalized ketal aldehyde and a 2,6-dihydroxybenzoic acid is the key step in the synthesis of (-)-berkelic acid confirming Fuerstner's reassignment of the stereochemistry at C18 and C1
- Wu, Xiaoxing,Zhou, Jingye,Snider, Barry B.
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supporting information; experimental part
p. 1283 - 1286
(2009/06/30)
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- Enantioselective epoxidation of terminal alkenes to (R)- and (S)-epoxides by engineered cytochromes P450 BM-3
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Cytochrome P450 BM-3 from Bacillus megaterium was engineered for enantioselective epoxidation of simple terminal alkenes. Screening saturation mutagenesis libraries, in which mutations were introduced in the active site of an engineered P450, followed by recombination of beneficial mutations generated two P450 BM-3 variants that convert a range of terminal alkenes to either (R)- or (S)epoxidc (up to 83 % ee) with high catalytic turnovers (up to 1370) and high epoxidation selectivities (up to 95%). A biocatalytic system using E. coli lysates containing P450 variants as the epoxidation catalysts and in vitro NADPH regeneration by the alcohol dehydrogenase from Thermoanaerobium brockii generates each of the epoxide enantiomers, without additional cofactor.
- Kubo, Takafumi,Peters, Matthew W.,Meinhold, Peter,Arnold, Frances H.
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p. 1216 - 1220
(2007/10/03)
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- Concise enantiospecific synthesis of (+)-calvine
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We report herein an efficient enantiospecific synthesis of (+)-calvine in nine steps from (R)-epichlorohydrine. The convergent synthesis is based on an olefin cross-metathesis (CM) reaction of a chiral homoallylamine and an enone. Subsequent reductive cyc
- Dewi-Wülfing, Purnama,Gebauer, Julian,Blechert, Siegfried
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p. 487 - 489
(2007/10/03)
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- Enzyme Assisted Synthesis of Enantiomerically Pure δ-Lactones
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Both enantiomers series of a wide variety of optically pure 6-alkylated δ-lactones - saturated as well as unsaturated - were prepared via an enzyme mediated route.The key reaction step is the nucleophilic ring opening of enantiomerically pure alkyl-oxiranes, accessible via the corresponding β-hydroxythioesters which can be obtained enantiomerically pure via enzyme catalyzed kinetic resolutions.
- Haase, Bernhard,Schneider, Manfred P.
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p. 1017 - 1026
(2007/10/02)
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- Enantioselective synthesis of epoxides via Sharpless epoxidation of alkenylsilanols
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Enantioselective synthesis of simple epoxides can be achieved by Sharpless epoxidation of alkenylsilanols followed by protodesilylation of the chiral epoxysilanols.The approach has been applied to the synthesis of frontalin.
- Chan, T. H.,Chen, L. M.,Wang, D.,Li, L. H.
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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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- Synthesis and Properties of Optically Active α-Aryl-γ-alkyl-γ-lactones as Chiral Dopants for Ferroelectric Liquid Crystals
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Optically active α-aryl-γ-alkyl-γ-lactones were synthesized from chiral epichlorohydrin in several steps and found to be good chiral dopants for ferroelectric liquid crystals (FLCs).Relationship between molecular structures and properties is discussed.
- Sakaguchi, Kazuhiko,Kitamura, Tohru,Shiomi, Yutaka,Koden, Mitsuhiro,Kuratate, Tomoaki
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p. 1383 - 1386
(2007/10/02)
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- Enantiodivergent Synthesis of Both Enantiomers of Sulcatol and Matsutake Alcohol from (R)-Epichlorohydrin
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Enantiodivergent synthesis of both enantiomers of sulcatol, an aggregation pheromone of Gnathotrichus sulcatus, and matsutake alcohol, a flavor compound of the mushroom Tricholoma matsutake, has been established using (R)-epichlorohydrin as common chiral precursor.
- Takano, Seiichi,Yanase, Masashi,Takahashi, Michiyasu,Ogasawara, Kunio
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p. 2017 - 2020
(2007/10/02)
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