- Asymmetric synthesis of (+)-stagonolide C and (-)-aspinolide A via organocatalysis
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A new enantioselective synthesis of two important fungal metabolites, (+)-stagonolide C and (-)-aspinolide A, has been described from readily available raw materials. Proline catalyzed asymmetric α-aminooxylation and Jorgensen's epoxidation of aldehydes a
- Shelke, Anil M.,Rawat, Varun,Suryavanshi, Gurunath,Sudalai, Arumugam
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Read Online
- Concise and protecting group-free synthesis of botryolide-E
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A simple highly concise protective group-free synthesis of botryolide-E from (R)-propylene oxide was developed using Hoveyda Grubbs cross metathesis, Still's modified Horner-Wadsworth-Emmons reaction, and Sharpless asymmetric dihydroxylation, as key steps.
- Chandra Rao,Kumar Reddy,Shekhar,Venkateswarlu
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Read Online
- Total synthesis of (–)-cephalosporolide D
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In this communication, a concise and efficient synthetic route for the synthesis of (–)-Cephalosporolide D in enantioselective way has been described. In this synthesis, Mitsunobu esterification and Ring Closing Metathesis (RCM) for macrocyclic ring formation have been applied as key steps.
- Kalavakuntla, Chiranjeevi,Kummari, Vijaya Babu,Yadav, Jhillu Singh
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- Copper-Catalyzed Enantiotopic-Group-Selective Allylation of gem-Diborylalkanes
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We report a copper-catalyzed enatiotopic-group-selective allylation of gem-diborylalkanes with allyl bromides. The combination of copper(I) bromide and H8-BINOL derived phosphoramidite ligand proved to be the most effective catalytic system to provide various enantioenriched homoallylic boronate esters, containing a boron-substituted stereogenic center that is solely derived from gem-diborylalkanes, in good yields with high enantiomeric ratios under mild conditions. Experimental and theoretical studies have been conducted to elucidate the reaction mechanism, revealing how the enatiotopic-group-selective transmetalation of gem-diborylalkanes with chiral copper complex occurs to generate chiral α-borylalkyl-copper species for the first time. Additional synthetic applications to the synthesis of various chiral building blocks are also included.
- Kim, Minjae,Park, Bohyun,Shin, Minkyeong,Kim, Suyeon,Kim, Junghoon,Baik, Mu-Hyun,Cho, Seung Hwan
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supporting information
p. 1069 - 1077
(2021/01/25)
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- A Unified Synthetic Approach to Optically Pure Curvularin-Type Metabolites
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A unified and concise approach to the synthesis of nine curvularin-type metabolites and two analogues has been developed with few steps and high yields. Among them, sumalactones A-D were synthesized for the first time. The key steps in this approach inclu
- Allu, Srinivasa Rao,Banne, Sreenivas,Jiang, Jia,Qi, Na,Guo, Jian,He, Yun
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p. 7227 - 7237
(2019/06/07)
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- A Short Synthesis of (+)-Brefeldin C through Enantioselective Radical Hydroalkynylation
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A very concise total synthesis of (+)-brefeldin C starting from 2-furanylcyclopentene is described. This approach is based on an unprecedented enantioselective radical hydroalkynylation process to introduce the two cyclopentane stereocenters in a single step. The use of a furan substituent allows a high trans diastereoselectivity to be achieved during the radical process and it contains the four carbon atoms C1–C4 of the natural product in an oxidation state closely related to the one of the target molecule. The eight-step synthesis requires six product purifications and it provides (+)-brefeldin C in 18 % overall yield.
- Gn?gi, Lars,Martz, Severin Vital,Meyer, Daniel,Sch?rer, Robin Marc,Renaud, Philippe
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supporting information
p. 11646 - 11649
(2019/08/30)
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- A facile, efficient and selective deprotection of p-methoxy benzyl ethers using zinc (Ii) trifluoromethanesulfonate
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Deprotection is significant and conducted over mild reaction conditions, in order to restrict any more side reactions with sensitive functional groups as well as racemization or epimerization of stereo center because the protective groups are often cleaved at last stage in the synthesis. P-Methoxy benzyl (PMB) ether appears unique due to its easy introduction and removal than the other benzyl ether protecting groups. A facile, efficient and highly selective cleavage of P-methoxy benzyl ethers was reported by using 20 mole% Zinc (II) Trifluoromethanesulfonate at room temperature in acetonitrile solvent over 15-120 min. time period. To study the generality of this methodology, several PMB ethers were prepared from a variety of substrates having different protecting groups and subjected to deprotection of PMB ethers using Zn(OTf)2 in acetonitrile. In this methodology, zinc triflate cleaves only PMB ethers without affecting acid sensitivity, base sensitivity and also chiral epoxide groups.
- Chandrasekhar, Choragudi,Rao, Mannam Subba,Sireesha, Reddymasu,Sreenivasulu, Reddymasu
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p. 955 - 958
(2019/11/22)
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- Carbohydrate/DBU Cocatalyzed Alkene Diboration: Mechanistic Insight Provides Enhanced Catalytic Efficiency and Substrate Scope
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A mechanistic investigation of the carbohydrate/DBU cocatalyzed enantioselective diboration of alkenes is presented. These studies provide an understanding of the origin of stereoselectivity and also reveal a strategy for enhancing reactivity and broadening the substrate scope.
- Yan, Lu,Meng, Yan,Haeffner, Fredrik,Leon, Robert M.,Crockett, Michael P.,Morken, James P.
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supporting information
p. 3663 - 3673
(2018/03/21)
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- Synthesis and Stereochemical Assignment of Arenolide
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The convergent synthesis of candidate stereoisomers of the natural product arenolide was accomplished using recently developed catalytic boron-based reactions. Comparison of the spectral data for candidate structures with that reported for the authentic natural product revealed the likely stereostructure of the natural compound.
- Liu, Xun,Sun, Chunrui,Mlynarski, Scott,Morken, James P.
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supporting information
p. 1898 - 1901
(2018/04/16)
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- [1,3]thiazin-2-amine compounds as well as applications and pharmaceutical compositions thereof
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The invention relates to [1,3]thiazin-2-amine compounds as well as applications and pharmaceutical compositions thereof, and belongs to the field of BACE (beta-site amyloid precursor protein cleavingenzyme) inhibitors. The [1,3]thiazid-2-amine compounds are compounds, pharmaceutically acceptable salts, stereoisomers, solvates, or prodrugs represented by a formula (I), and the formula (I) is shownin the description. The [1,3]thiazin-2-amine compounds provided by the invention have good inhibiting effects on BACE, and can be used for the preparation of medicines for treating neurodegenerativediseases such as alzheimer diseases.
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Paragraph 0136-0138; 0140; 0142
(2018/04/21)
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- Total synthesis of diplodialides C and D
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A highly convergent, stereoselective total synthesis of diplodialides C and D is described. The protocol involves the use of regioselective ring opening of a chiral epoxide, sequential double alkylation of 1,3-dithiane with a bromide and a chiral epoxide,
- Ramanujan, Vyasabhattar,Kumar, Chebolu Naga Sesha Sai Pavan
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p. 332 - 340
(2019/01/03)
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- Nickel-Catalyzed Enantioselective Conjunctive Cross-Coupling of 9-BBN Borates
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Catalytic enantioselective conjunctive cross-coupling between 9-BBN borate complexes and aryl electrophiles can be accomplished with Ni salts in the presence of a chiral diamine ligand. The reactions furnish chiral 9-BBN derivatives in an enantioselective fashion and these are converted to chiral alcohols and amines, or engaged in other stereospecific C?C bond forming reactions.
- Chierchia, Matteo,Law, Chunyin,Morken, James P.
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supporting information
p. 11870 - 11874
(2017/09/06)
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- Mechanistic Studies on a Cu-Catalyzed Asymmetric Allylic Alkylation with Cyclic Racemic Starting Materials
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Mechanistic studies on Cu-catalyzed asymmetric additions of alkylzirconocene nucleophiles to racemic allylic halide electrophiles were conducted using a combination of isotopic labeling, NMR spectroscopy, kinetic modeling, structure-activity relationships, and new reaction development. Kinetic and dynamic NMR spectroscopic studies provided insight into the oligomeric Cu-ligand complexes, which evolve during the course of the reaction to become faster and more highly enantioselective. The Cu-counterions play a role in both selecting different pathways and in racemizing the starting material via formation of an allyl iodide intermediate. We quantify the rate of Cu-catalyzed allyl iodide isomerization and identify a series of conditions under which the formation and racemization of the allyl iodide occurs. We developed reaction conditions where racemic allylic phosphates are suitable substrates using new phosphoramidite ligand D. D also allows highly enantioselective addition to racemic seven-membered-ring allyl chlorides for the first time.1H and2H NMR spectroscopy experiments on reactions using allylic phosphates showed the importance of allyl chloride intermediates, which form either by the action of TMSCl or from an adventitious chloride source. Overall these studies support a mechanism where complex oligomeric catalysts both racemize the starting material and select one enantiomer for a highly enantioselective reaction. It is anticipated that this work will enable extension of copper-catalyzed asymmetric reactions and provide understanding on how to develop dynamic kinetic asymmetric transformations more broadly.
- Rideau, Emeline,You, Hengzhi,Sidera, Mireia,Claridge, Timothy D. W.,Fletcher, Stephen P.
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supporting information
p. 5614 - 5624
(2017/04/27)
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- Total synthesis, biological evaluation of dendrodolides A–D and their analogues
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A concise total synthesis of dendrodolides A–D (1–4) has been accomplished in 10 steps from commercially available (R)-propylene oxide and 3-buten-1-ol as starting materials. The key steps involved in the synthesis are Jacobsen hydrolytic kinetic resolution, epoxide ring opening with 2-allyl-1, 3-dithiane, Yamaguchi esterification and ring-closing metathesis (RCM). In addition, a series of ester derivatives were prepared utilizing Yamaguchi esterification at the C-3 position of the dendrodolide core and screened for their efficacy against cancer cell lines.
- Poornima,Venkanna,Swetha,Kamireddy, Karthik reddy,Siva, Bandi,Phani Babu,Ummanni, Ramesh,Babu, K. Suresh
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p. 4789 - 4797
(2016/07/18)
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- Asymmetric Synthesis of Borylalkanes via Copper-Catalyzed Enantioselective Hydroallylation
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An efficient synthetic method for preparing enantioenriched secondary borylalkanes has been achieved through a copper-catalyzed regio- and enantioselective hydroallylation of alkenyl boronates and boramides employing hydrosilanes and allylic phosphates. In the presence of a copper catalyst with a chiral Walphos ligand, a range of alkenylboron compounds with an aryl, heteroaryl, or alkyl substituent produced secondary homoallylic alkylboron compounds in good yields and with high enantioselectivities up to 99% ee. The utility of the resulting alkylboronates was demonstrated in an efficient synthesis of (S)-massoialactone.
- Han, Jung Tae,Jang, Won Jun,Kim, Namhyeon,Yun, Jaesook
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supporting information
p. 15146 - 15149
(2016/12/06)
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- First Stereoselective Synthesis of the Cytotoxic Polyketide (4R)-1-(3,5-Dihydroxyphenyl)-4-hydroxypentan-2-one
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The first stereoselective synthesis of the cytotoxic polyketide (4R)-1-(3,5-dihydroxyphenyl)-4-hydroxypentan-2-one (1) was achieved from readily available propylene oxide and 3,5-dimethoxybenzyl alcohol. The synthesis involves Jacobsen's hydrolytic kinetic resolution (HKR) and Grignard reaction as key steps.
- Rajendra Prasad, Kothakonda,Purushotham Reddy, Sudina,Suresh Babu, Katragadda,Madhusudana Rao, Janaswamy
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p. 143 - 147
(2015/10/19)
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- Synthesis of (3R,5S)-5-hydroxy-de-O-methyllasiodiplodin: A facile and stereoselective approach
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A concise and facile synthesis of (3R,5S)-5-hydroxy-de-O-methyllasiodiplodin has been demonstrated in 12 steps starting from methylacetoacetate and (±)propylene oxide. The key reactions involved are Jacobsen's hydrolytic kinetic resolution, Sharpless asymmetric epoxidation, Mitsunobu, and ring closing metathesis reaction for the construction of macrolactone with two chiral substitutions on it.
- Bujaranipalli, Sheshurao,Das, Saibal
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p. 3747 - 3749
(2015/06/08)
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- Synthetic Studies toward the C32-C46 Segment of Hemicalide. Assignment of the Relative Configuration of the C36-C42 Subunit
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The synthesis of five diastereomeric model compounds incorporating the C32-C46 segment of the antitumor marine natural product hemicalide has been achieved through a convergent approach relying on the 1,4-addition of an alkenyl boronate to an α,β-unsaturated δ-lactone followed by α-hydroxylation of an enolate and a Julia-Kocienski olefination. Comparison of the 1H and 13C NMR data of the model compounds with those of hemicalide enabled the assignment of the relative configuration of the C36-C42 subunit. (Chemical Equation Presented).
- Specklin, Simon,Boissonnat, Guillaume,Lecourt, Camille,Sorin, Geoffroy,Lannou, Marie-Isabelle,Ardisson, Janick,Sautel, Fran?ois,Massiot, Georges,Meyer, Christophe,Cossy, Janine
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supporting information
p. 2446 - 2449
(2015/05/27)
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- The first stereoselective synthesis of dendrodolide A
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The first stereoselective total synthesis of natural product, dendrodolide A (1) is described from readily available (R)-propylene oxide and 3-buten-1-ol as starting materials. The synthesis was achieved in 10 steps with an overall yield of 19.1%. The key steps involved in the synthesis are Jacobsen hydrolytic kinetic resolution, epoxide ring opening with 2-allyl-1, 3-dithiane, Yamaguchi esterification, and ring-closing metathesis (RCM).
- Venkanna,Siva,Poornima,Babu, K. Suresh,Rao, J. Madhusudana
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p. 403 - 406
(2014/01/06)
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- Asymmetric total synthesis of stagonolide F
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A highly convergent stereoselective total synthesis of stagonolide F is described starting from commercially available 5-hexen 1-ol using asymmetric dihydroxylation, Jacobsen's hydrolytic kinetic resolution (HKR), regioselective epoxide ring opening with vinyl Grignard reaction, esterification, and ring-closing metathesis (RCM) as key steps.
- Chinnababu,Reddy, S. Purushotham,Babu, K. Suresh,Venkateswarlu
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p. 2886 - 2891
(2014/09/29)
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- Concise total synthesis of botryolide B
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An efficient total synthesis of botryolide B was achieved in 9 longest linear steps with 22% overall yield via esterification of a carboxylic acid with an alcohol fragment and a ring closing metathesis (RCM) reaction as pivotal steps to construct the macrolactone ring system. Our novel approach for the synthesis of the 2-alkene-1,5-diol fragment was achieved by a ring closing metathesis reaction followed by a reductive opening strategy, whereas the carboxylic acid fragment was accessed from commercially available (R)-(+)-α-hydroxy-γ-butyrolactone in three steps.
- Mohapatra, Debendra K.,Umamaheshwar, Gonela,Rao, M. Mallikarjuna,Umadevi, Deivasigamani,Yadav, Jhillu S.
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p. 8335 - 8340
(2014/02/14)
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- Stereoselective total synthesis of cochliomycin A
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A convergent and stereoselective synthesis of cochliomycin A, a 14-membered resorcyclic acid lactone, based on chiron approach is described. The key reactions involved olefin cross-metathesis and sodium hydride promoted one-pot intramolecular lactonization. l-Arabinose was used as a chiral pool material for the construction of the key fragment.
- Wang, Linlin,Gao, Yangguang,Liu, Jun,Cai, Chao,Du, Yuguo
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p. 2616 - 2620
(2014/04/03)
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- First stereoselective total synthesis of Neocosmosin A: A facile approach
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First stereoselective concise synthesis of Neocosmosin A, with in vitro binding affinity for human opioid and cannabinoid receptors, has been reported using readily available starting materials such as methylacetoacetate, cyclohexanone, and homoallyl alco
- Dachavaram, Soma Shekar,Kalyankar, Kondbarao Balasaheb,Das, Saibal
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supporting information
p. 5629 - 5631
(2014/12/11)
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- Convergent synthesis of (+)-xestodecalactone A via a Pd-catalyzed α-arylation reaction
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The convergent total synthesis of (+)-xestodecalactone A (1) is reported. In addition, a formal synthesis of (+)-sporostatin has been accomplished by means of intercepting a previously reported intermediate en route to 1. The key reaction utilized was a convergent Pd-catalyzed α-arylation between a boronic acid and an α-bromoester.
- De Joarder, Dripta,Jennings, Michael P.
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p. 3990 - 3992
(2013/07/25)
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- Synthesis and glycosidase inhibition studies of 5-methyl-substituted tetrahydroxyindolizidines and -pyrrolizidines related to natural hyacinthacines B
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The synthesis of three tetrahydroxyindolizidines and one tetrahydroxypyrrolizidine related to natural hyacinthacines B and their biological evaluation as glycosidase inhibitors is reported. The target molecules were obtained through highly stereoselective cycloadditions between sugriched allylic and homoallylic alcohols. This allowed the installation of a methyl group at C5 - a common feature of many natural hyacinthacines - with high control over the stereoselectivity. The new compounds inhibit amyloglucosidase from Aspergillus niger and β-glucosidase from almonds. Compound 1 is a competitive inhibitor of amyloglucosidase and shows a fair selectivity towards this enzyme. The presence of C5-Me substitution in indolizidines 2 and 3 slightly diminishes the inhibitory activity towards amyloglucosidase whereas it improves the inhibitory properties towards β-glucosidase. Cycloaddition between a carbohydrate-derived nitrone and suitable chemoenzymatically prepared enantioenriched allylic and homoallylic alcohols allowed the straightforward synthesis of three tetrahydroxyindolizidines and one tetrahydroxypyrrolizidine related to natural hyacinthacines B. They inhibit amyloglucosidase from Aspergillus niger and β-glucosidase from almonds. Copyright
- Martella, Daniele,Cardona, Francesca,Parmeggiani, Camilla,Franco, Francisco,Tamayo, Juan A.,Robina, Inmaculada,Moreno-Clavijo, Elena,Moreno-Vargas, Antonio J.,Goti, Andrea
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p. 4047 - 4056
(2013/07/19)
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- Towards the total synthesis of marineosin A: Construction of the macrocyclic pyrrole and an advanced, functionalized spiroaminal model
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Herein, we describe the enantioselective construction of the 12-membered macrocyclic pyrrole core of marineosin A in 5.1 % overall yield from (S)-propylene oxide. The route features a key Stetter reaction to install a 1,4-diketone, which is subjected to Paal-Knorr pyrrole synthesis and ring-closing metathesis to afford the macrocycle. A divergence point in the synthetic scheme also enabled access to a highly functionalized spiroaminal model system through an acid-mediated hydroxy oxo amide cyclization strategy. Copyright
- Aldrich, Leslie N.,Berry, Cynthia B.,Bates, Brittney S.,Konkol, Leah C.,So, Miranda,Lindsley, Craig W.
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supporting information
p. 4215 - 4218
(2013/07/26)
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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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p. 1737 - 1742
(2012/07/31)
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- Synthesis and structure of two new mycolactones isolated from M. ulcerans subsp. shinshuense
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Two new mycolactones, mycolactones S1 and S2, were isolated from culture agar of Mycobacterium ulcerans subsp. shinshuense. Their structures were established in a three-step procedure: (1) probable structures were speculated from MS analysis; (2) candidates were synthesized; (3) HPLC profiles were established for identification of the natural products. Newly isolated mycolactones correspond to the oxidized forms of mycolactone A/B, the causative toxin of Buruli ulcer, isolated from Mycobacterium ulcerans.
- Hande, Sudhir M.,Kazumi, Yuko,Lai, W. George,Jackson, Katrina L.,Maeda, Shinji,Kishi, Yoshito
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supporting information
p. 4618 - 4621
(2012/10/29)
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- One-flask tethered ring closing metathesis-electrocyclic ring opening for the highly stereoselective synthesis of conjugated Z/E-dienes
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A one-flask reaction sequence comprising ring closing metathesis (RCM) of butenoates derived from allylic alcohols and a base-mediated ring opening gives 2Z,4E-configured dienoic acids in high yields and stereoselectivities. Application of the method to the synthesis of the natural product fusanolide A suggests that the originally published structure was erroneously assigned and should be revised. Ring closing metathesis (RCM) of butenoates derived from allylic alcohols can be combined with base-induced ring opening in a one-flask sequence. In this way, dienoic acids become accessible in an operationally simple procedure in very high yields and excellent stereoselectivities, with the tether remaining in the product as a valuable functional group for further transformations. Copyright
- Schmidt, Bernd,Kunz, Oliver
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supporting information; scheme or table
p. 1008 - 1018
(2012/03/27)
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- Stereoselective synthesis of ophiocerins A and C
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An efficient synthesis of ophiocerins A and C has been achieved via a common intermediate. The stereogenic centers were generated by means of Jacobsen's hydrolytic kinetic resolution and Sharpless kinetic resolution.
- Show, Krishanu,Gupta, Priti,Kumar, Pradeep
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experimental part
p. 1212 - 1217
(2011/10/30)
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- First total syntheses of (3 R,5 R)-sonnerlactone and (3 r,5 s)-sonnerlactone
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First total syntheses of the macrocyclic natural products (3R,5R)-sonnerlactone and (3R,5S)-sonnerlactone, two new metabolites isolated from the endophytic fungus strain Zh6-B1, have been accomplished in eleven steps with 22% overall yield starting from enantiomerically pure (R)-propylene oxide prepared by hydrolytic kinetic resolution. Other key steps are Sharpless epoxidation, reductive elimination of iodo epoxide, and ring-closing-metathesis reaction for the construction of the macrolactone. Georg Thieme Verlag Stuttgart · New York.
- Thirupathi, Barla,Gundapaneni, Raghava R.,Mohapatra, Debendra K.
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scheme or table
p. 2667 - 2670
(2011/12/04)
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- Novel synthesis of stagonolide-F, putaminoxin and aspinolide-A
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Novel synthesis of putaminoxin, stagonolide-F and aspinolide-A have been achieved by utilizing (S) and (R)- malic acid. The key feature of the synthetic strategy includes Horner-Wittig olefination, double bond reduction and Steglich esterification. Olefinic acid for putaminoxin and stagonolide-F was prepared from (S)-malic acid whereas olefinic acid for aspinolide-A was prepared from (R)-malic acid and olefinic alcohols for putaminoxin, stagonolide-F and aspinolide-A were prepared by using Brown's asymmetric allylboration.
- Kamal, Ahmed,Reddy, Papagari Venkat,Balakrishna, Moku,Prabhakar, Singaraboina
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p. 143 - 149
(2013/01/10)
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- A unified total synthesis of aspergillides A and B
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An enantioselective total synthesis of aspergillides A and B has been accomplished based on a unified strategy, wherein a hydroxy-directed, highly chemoselective olefin cross-metathesis and a diastereoselective intramolecular oxa-conjugate cyclization were employed to forge the 2,6-substituted tetrahydropyran substructure.
- Fuwa, Haruhiko,Yamaguchi, Hiroshi,Sasaki, Makoto
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supporting information; experimental part
p. 1848 - 1851
(2010/09/16)
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- An enantioselective total synthesis of aspergillides A and B
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An enantioselective total synthesis of aspergillides A and B has been accomplished on the basis of a unified synthetic strategy that exploits stereodivergent intramolecular oxa-conjugate cyclization and Yamaguchi macrolactonization.
- Fuwa, Haruhiko,Yamaguchi, Hiroshi,Sasaki, Makoto
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experimental part
p. 7492 - 7503
(2010/12/19)
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- Enantioselective synthesis of decarestrictine J
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An efficient total synthesis of decarestrictine J has been achieved using ring-closing metathesis and Yamaguchi esterification as key steps. The stereogenic centres were generated by means of iterative hydrolytic kinetic resolution (HKR) of racemic epoxides.
- Chowdhury, Partha Sarathi,Gupta, Priti,Kumar, Pradeep
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scheme or table
p. 7188 - 7190
(2010/02/28)
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- First asymmetric total synthesis of aspinolide A
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The first total synthesis of aspinolide A has been achieved using ring-closing metathesis as a key step. The stereogenic centers were generated by means of hydrolytic kinetic resolution (HKR) of racemic epoxides.
- Chowdhury, Partha Sarathi,Gupta, Priti,Kumar, Pradeep
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scheme or table
p. 7018 - 7020
(2010/02/28)
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- Concise synthesis of stagonolide-F by ring closing metathesis approach and its biological evaluation
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The first total synthesis of 9-membered macrolide, stagonolide-F (3), starting from commercially available 1,5-pentane diol is reported. A combination of Jacobsen's hydrolytic kinetic resolution (HKR) and Sharpless epoxidation is used for the creation of two stereogenic centers, while ring-closing metathesis (RCM) strategy was used for the construction of the lactone ring. The molecule synthesized exhibited potent antifungal, antibacterial and cytotoxic activities against all the tested strains.
- Perepogu, Arun Kumar,Raman,Murty,Rao, Vaidya Jayathirtha
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body text
p. 46 - 51
(2009/08/07)
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- First stereoselective total synthesis of sporostatin and determination of absolute configuration
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The first simple and efficient total synthesis of sporostatin has been accomplished in five steps starting from (S)-propylene oxide. The synthesis utilizes simple reactions such as esterification, cross-metathesis, and intramolecular Friedel-Crafts reacti
- Yadav,Thrimurtulu,Uma Gayathri,Subba Reddy,Prasad
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scheme or table
p. 790 - 792
(2009/08/07)
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- An efficient total synthesis of decarestrictine D
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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
- Gupta, Priti,Kumar, Pradeep
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scheme or table
p. 1195 - 1202
(2009/04/07)
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- An enantioselective total synthesis of (+)-aigialospirol
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(Chemical Equation Presented) A concise and enantioselective total synthesis of (+)-aigialospirol is described here, featuring the first complex natural product synthesis that employs a cyclic ketal-tethered ring-closing metathesis strategy and an unexpected stereoselective epimerization of a benzylic hydroxyl group. The 15-step synthetic sequence illustrates the proof-of-concept that such an approach can be competitive with the classical spiroketal formation in the natural product synthesis.
- Figueroa, Ruth,Hsung, Richard P.,Guevarra, Christie C.
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p. 4857 - 4859
(2008/03/15)
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- Stereoselective synthesis of (+)-cryptocarya diacetate by an iterative Prins cyclisation and reductive cleavage sequence
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A highly stereoselective synthesis of (+)-cryptocarya diacetate is achieved through our recently developed strategy for the construction of 1,3-diols via Prins cyclisation. The route relies mainly on the reductive cleavage of allylic ethers, ozonolysis and Wittig olefination along with Prins cyclisation.
- Yadav,Rao, P. Purushothama,Reddy, M. Sridhar,Rao, N. Venkateswar,Prasad
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p. 1469 - 1471
(2008/02/02)
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- Stereoselective synthesis of tarchonanthuslactone via the Prins cyclisation
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The stereoselective total synthesis of tarchonanthuslactone, a polyketide natural product, has been achieved. The synthesis exploits the high stereochemical control in the Prins cyclisation along with ring closing metathesis (RCM) as a key step.
- Yadav,Kumar, N. Niranjan,Reddy, M. Sridhar,Prasad
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p. 2689 - 2694
(2007/10/03)
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- A simple and efficient approach to 1,3-polyols: Application to the synthesis of cryptocarya diacetate
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A highly enantio- and stereoselective synthetic strategy for both syn-and anti-1,3-polyols has been developed. The sequence involves iterative Jacobsen's hydrolytic kinetic resolution (HKR), diastereoselective iodine-induced electrophilic cyclization, and ring-closing metathesis (RCM). This protocol has subsequently been utilized for the synthesis of cryptocarya diacetate, a natural product with broad range of biological activity.
- Kumar, Pradeep,Gupta, Priti,Vasudeva Naidu
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p. 1397 - 1402
(2008/01/27)
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- HYDROXYBENZOATE SALTS OF METANICOTINE COMPOUNDS
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Patients susceptible to or suffering from conditions and disorders, such as central nervous system disorders, are treated by administering to a patient in need thereof compositions that are hydroxybenzoate salts of E-metanicotine-type compounds. The forma
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Page/Page column 42
(2008/06/13)
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- Enantioselective synthesis of tarchonanthuslactone via iterative hydrolytic kinetic resolution
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A short and practical enantioselective synthesis of tarchonanthuslactone has been achieved in high diastereomeric excess using iterative Jacobsen's hydrolytic kinetic resolution and ring closing metathesis as the key steps.
- Gupta, Priti,Naidu, S. Vasudeva,Kumar, Pradeep
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p. 6571 - 6573
(2007/10/03)
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- Compounds capable of activating cholinergic receptors
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The present invention generally relates to nicotinic compounds, in the form of aryl substituted olefinic compounds, as well as pro-drug, N-oxide, metabolite and pharmaceutically acceptable salt forms thereof. Methods of modulating neurotransmitter release via administration of the compounds, pro-drugs, N-oxides and/or pharmaceutically acceptable salts are also disclosed.
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- Asymmetric allyl- and crotylboration with the robust, versatile, and recyclable 10-TMS-9-borabicyclo[3.3.2]decanes
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The remarkable versatility and selectivity of the 10-(trimethylsilyl)-9- borabicyclo[3.3.2]decanes (10-TMS-9-BBDs) in the allyl- and crotylboration of representative aldehydes are reported. The new reagents are prepared through air-stable crystalline pseudoephedrine borinic ester complexes of the 10-TMS-9-BBDs (4), which are available in 63% overall yield from B-MeO-9-BBN through a simple two-step procedure. These complexes 4 are directly converted to the corresponding B-allyl-10-TMS-9-BBDs (1) with allylmagnesium bromide, which either can be isolated (98%) or used in situ for the allylations. The remarkable enantioselectivity (96 to ≥99% ee) of these reagents in the rapid (3 h), asymmetric allylboration process at -78 °C is only slightly diminished when it is conducted at 25 °C, a phenomenon attributable to its rigid bicyclic structure. In addition to providing the homoallylic alcohols 6 efficiently (68-80%), the procedure also permits the efficient recovery of 4 (68-84%) for the direct regeneration of 1. Alternatively, an oxidative workup procedure can be used for the preparation of 6. The reagent gives predictable stereochemistry and exhibits an extremely high level of reagent control in the allylboration of D-glyceraldehyde acetonide. A simple and efficient procedure has been developed for the preparation of all four geometric and enantiomeric isomers of the B-crotyl-10-TMS-9-BBDs (10) from optically pure enantiomers of B-MeO-10-TMS-9-BBD (3). These reagents 10 also add rapidly (3 h) and efficiently to representative aldehydes at -78 °C, providing ready access to all four of the possible stereoisomers of the β-methyl homoallylic alcohols 12-15 (69-92%) in high dr (≥98:2) and ee (94-99%).
- Burgos, Carlos H.,Canales, Eda,Matos, Karl,Soderquist, John A.
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p. 8044 - 8049
(2007/10/03)
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- A new total synthesis of (+)-brefeldin C
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A new synthesis of (+)-brefeldin C featuring a Bolm desymmetrisation reaction, a B-alkyl Suzuki-Miyaura cross-coupling and a Carreira alkynylation reaction as the key steps is reported.
- Archambaud, Sylvie,Aphecetche-Julienne, Karine,Guingant, André
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p. 139 - 143
(2007/10/03)
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- A chemoenzymatic total synthesis of the phytotoxic undecenolide (-)-cladospolide A.
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An eleven-step synthesis of the title compound (1) from biocatalytically-derived and enantiomerically pure 'building blocks' alcohol (R)-(-)-9 and ester 13 is described. Attempts to construct the twelve-membered lactone ring of cladospolide A in a direct manner by using a ring-closing metathesis (RCM) reaction failed. However, a ten-membered lactone 19, could be constructed by such means and this was then subject to a two-carbon homologation sequence involving, inter alia, Wadsworth-Horner-Emmons and Yamaguchi lactonisation reactions in the closing stages of the synthesis. The impact of substituent stereochemistries and protecting groups on the RCM reaction leading to various ten-membered lactones is also described.
- Banwell, Martin G,Loong, David T J
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p. 2050 - 2060
(2007/10/03)
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- Biocatalytic oxidative kinetic resolution of sec-alcohols: Stereocontrol through substrate-modification
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Whole lyophilised cells of Rhodococcus ruber DSM 44541 were employed for the oxidative kinetic resolution of sec-alcohols using acetone as hydrogen acceptor. The enantioselectivity of this process could be controlled effectively by introducing C-C multiple bonds into substrates, which were inefficiently recognised, in particular short-chain (ω-1)-alcohols and (ω-2)-analogs. Thus, the enantioselectivities of rac-2-pentanol (E=16.8) and rac-3-octanol (E=13.3) were significantly improved by introducing a C=C bond adjacent to the alcohol moiety to give racemic (E)-pent-3-en-2-ol and 4-(E)-octen-3-ol, which were resolved with excellent selectivities (E >100 and 50, respectively). In addition, it was found that high stereodifferentiation between the E- and Z-configured double bonds occurred, as the corresponding (Z)-isomers were not converted. Similar selectivity-enhancing effects were observed with acetylenic analogs.
- Stampfer, Wolfgang,Kosjek, Birgit,Faber, Kurt,Kroutil, Wolfgang
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p. 275 - 280
(2007/10/03)
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