- Unified Asymmetric Total Syntheses of (?)-Alotaketals A–D and (?)-Phorbaketal A
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The novel tricyclic spiroketal alotane-type sesterterpenoids showed strikingly different biological activities and potency with subtle structural alterations. Asymmetric total syntheses of the tricyclic sesterterpenoids (?)-alotaketals A–D and (?)-phorbaketal A were accomplished [29–31 steps from (?)-malic acid] in a collective way for the first time. The key features of the strategy included 1) a new cascade cyclization of vinyl epoxy δ-keto-alcohols to forge the common tricyclic spiroketal intermediate, 2) a late-stage allylic C?H oxidation, and 3) olefin cross-metathesis to install the different side chains.
- Cheng, Hang,Zhang, Zhihong,Yao, Hongliang,Zhang, Wei,Yu, Jingxun,Tong, Rongbiao
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Read Online
- Method for methyl heptanone to synthetize chiral citronellal
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The invention provides a method for methyl heptanone to synthetize chiral citronellal. The method includes the following steps: (1) performing methylenenation reaction on methyl heptanone and an organic tiron so that a 2,6-dimethyl-1,5-heptadiene intermediate with high yield; and (2) performing asymmetric hydroformylation on the heptadiene intermediate under the action of a homogeneous chiral rhodium catalyst so that a chiral citronellal product can be obtained. The main advantages of the method are as follows: the method is novel in synthetic method, a synthetic route is brief, and the chiralcitronellal product can be obtained by only two steps of reaction; the tiron can be used to perform the methylenenation reaction of the methyl heptanone, so that the 2,6-dimethyl-1,5-heptadiene can be obtained with high yield, and therefore, the method is higher than other existing known methods; and the method creatively utilizes the homogeneous chiral rhodium catalyst to realize the asymmetrichydroformylation of the 2,6-dimethyl-1,5-heptadiene, so that the method is high in reaction yield and excellent in stereoselectivity.
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Paragraph 0042; 0043; 0044; 0045; 0046-0059
(2019/05/08)
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- Oxidative Dehydroxymethylation of Alcohols to Produce Olefins
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Catalyst compositions for the conversion of aldehyde compounds and primary alcohol compounds to olefins are disclosed herein. Reactions include oxidative dehydroxymethylation processes and oxidative dehydroformylation methods, which are beneficially conducted in the presence of a sacrificial acceptor of H2 gas, such as N,N-dimethylacrylamide.
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Paragraph 0057; 0058
(2019/09/06)
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- Total Synthesis of Xanthoangelol B and Its Various Fragments: Toward Inhibition of Virulence Factor Production of Staphylococcus aureus
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As an alternative strategy to fight antibiotic resistance, two-component systems (TCSs) have emerged as novel targets. Among TCSs, master virulence regulators that control the expression of multiple virulence factors are considered as excellent antivirulence targets. In Staphylococcus aureus, virulence factor expression is tightly regulated by a few master regulators, including the SaeRS TCS. In this study, we used a SaeRS GFP-reporter system to screen natural compound inhibitors of SaeRS, and identified xanthoangelol B 1, a prenylated chalcone from Angelica keiskei as a hit. We have synthesized 1 and its derivative PM-56 and shown that 1 and PM-56 both had excellent inhibitory potency against the SaeRS TCS, as demonstrated by various in vitro and in vivo experiments. As a mode of action, 1 and PM-56 were shown to bind directly to SaeS and inhibit its histidine kinase activity, which suggests a possibility of a broad spectrum inhibitor of histidine kinases.
- Mizar, Pushpak,Arya, Rekha,Kim, Truc,Cha, Soyoung,Ryu, Kyoung-Seok,Yeo, Won-Sik,Bae, Taeok,Kim, Dae Wook,Park, Ki Hun,Kim, Kyeong Kyu,Lee, Seung Seo
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p. 10473 - 10487
(2018/11/23)
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- Tandem Catalysis: Transforming Alcohols to Alkenes by Oxidative Dehydroxymethylation
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We report a Rh-catalyst for accessing olefins from primary alcohols by a C-C bond cleavage that results in dehomologation. This functional group interconversion proceeds by an oxidation-dehydroformylation enabled by N,N-dimethylacrylamide as a sacrificial acceptor of hydrogen gas. Alcohols with diverse functionality and structure undergo oxidative dehydroxymethylation to access the corresponding olefins. Our catalyst protocol enables a two-step semisynthesis of (+)-yohimbenone and dehomologation of feedstock olefins.
- Wu, Xuesong,Cruz, Faben A.,Lu, Alexander,Dong, Vy M.
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supporting information
p. 10126 - 10130
(2018/08/23)
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- Selective Synthesis of Silacycles by Borane-Catalyzed Domino Hydrosilylation of Proximal Unsaturated Bonds: Tunable Approach to 1,n-Diols
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The tris(pentafluorophenyl)boron-catalyzed domino hydrosilylation of substrates carrying unsaturated functionalities in a proximal arrangement is presented to produce silacycles. Excellent levels of efficiency and selectivity were achieved in the cyclization by the deliberate choice of the hydrosilane reagents. The key to successful cyclic hydrosilylation is the reactivity enhancement of the second intramolecular hydrosilylation by a proximity effect. Not only dienes but also enones, enynes, ynones and enimines readily afford medium-sized silacycles under convenient and mild conditions. The cyclization proceeds with acceptable diastereoselectivity mainly controlled by the conformational bias towards inducing additional stereogenic centers. The silacycles obtained from this reaction were converted to 1,n-diols or 1,n-amino alcohols upon oxidation, thus rendering the present cyclization a powerful tool for accessing synthetically valuable building blocks. (Figure presented.).
- Shin, Kwangmin,Joung, Seewon,Kim, Youyoung,Chang, Sukbok
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supporting information
p. 3428 - 3436
(2017/09/25)
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- Rh-catalyzed C-C bond cleavage by transfer hydroformylation
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The dehydroformylation of aldehydes to generate olefins occurs during the biosynthesis of various sterols, including cholesterol in humans. Here, we implement a synthetic version that features the transfer of a formyl group and hydride from an aldehyde substrate to a strained olefin acceptor. A Rhodium(Xantphos)(benzoate) catalyst activates aldehyde carbon-hydrogen (C-H) bonds with high chemoselectivity to trigger carbon-carbon (C-C) bond cleavage and generate olefins at low loadings (0.3 to 2 mole percent) and temperatures (22° to 80°C). This mild protocol can be applied to various natural products and was used to achieve a three-step synthesis of (+)-yohimbenone. A study of the mechanism reveals that the benzoate counterion acts as a proton shuttle to enable transfer hydroformylation.
- Murphy, Stephen K.,Park, Jung-Woo,Cruz, Faben A.,Dong, Vy M.
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- A general and efficient aldehyde decarbonylation reaction by using a palladium catalyst
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A facile decarbonylation reaction of aldehydes has been developed by employing Pd(OAc)2. A wide variety of substrates are decarbonylated, without using any exogenous ligand for palladium as well as CO-scavenger.
- Modak, Atanu,Deb, Arghya,Patra, Tuhin,Rana, Sujoy,Maity, Soham,Maiti, Debabrata
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supporting information; experimental part
p. 4253 - 4255
(2012/05/04)
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- On the ethenolysis of natural rubber and squalene
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We report here the ethenolysis of squalene and natural rubber utilizing (NHC)(NHCewg)RuCl2(= CRR') and Grubbs-Hoveyda complexes. 0.01 mol% [Ru] per double bond are sufficient for extensive squalene cleavage, resulting in the formation of numerous terminal olefins, which were identified by GC/MS. The depolymerization of natural rubber requires 0.1 mol% [Ru] and leads to the formation of various oligomeric isoprenes, several of which (n = 2-6) were isolated and characterized.
- Wolf, Stefanie,Plenio, Herbert
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supporting information; experimental part
p. 2008 - 2012
(2011/10/09)
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- The iridium-catalyzed decarbonylation of aldehydes under mild conditions
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The catalytic decarbonylation of aldehydes has been developed using commercially available [IrCl(cod)]2 and PPh3 under mild conditions, and the method could be widely applicable to various substrates with different functionalities. The Royal Society of Chemistry.
- Iwai, Tomohiro,Fujihara, Tetsuaki,Tsuji, Yasushi
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experimental part
p. 6215 - 6217
(2009/05/06)
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- Geranic acid derivatives
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4-Methyl-4-(4-mlthylpent-3-en-1-yl)-2-oxetanone of formula (1): or its oligomer is an intermediate product for the preparation of a series of geranic acid derivatives, which are important synthetic building blocks in the preparation of perfumes and fragrances.
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- STUDIES ON THE CHEMISTRY OF DIOLS AND CYCLIC ETHERS-52. MECHANISM AND STEREOCHEMISTRY OF DEHYDRATION OF OXOLANES TO DIENES
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On γ-Al2O3, BPO4 and NaX zeolite, the dehydration of (+/-)-2,2,3,4,5,5-hexamethyloxolane (2) in the vapour phase leads to the formation of 2,3,4,5-tetramethyl-1,5-hexadiene (8) in a slow process, while meso-2,2,3,4,5,5-hexamethyloxolane (3) is converted to 2,3,4,5-tetramethyl-2,4-hexadiene (7) with high selectivity in a fast reaction.These differences in reaction rate and selectivity indicate that the dehydration of 2 takes place by an E2 mechanism.In contrast, the steric strain in 3 results in ring opening by an E1 mechanism.These conclusions are supported by the nonselective transformations of 2,2,5,5-tetramethyloxolane (1) and 2,2,6,6-tetramethyloxane (4), and the dehydration of 1, 2 and 3 in the presence of formic acid in the liquid phase.The experimental observation prove that both the reactivity and the reaction directions in the dehydration of stereoisomeric oxolanes are determined by steric factors.
- Molnar, Arpad,Bartok, Mihaly
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p. 131 - 142
(2007/10/02)
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- Process for the preparation of dienes and/or trienes
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Process for the preparation of dienes and/or trienes comprising reacting a polyolefinically unsaturated compound in the presence of a heterogeneous disproportionation catalyst with a compound according to the general formula STR1 wherein R1 and R2, which may be the same or different, each represents an alkyl, aryl, alkaryl or aralkyl group which may or may not contain one or more inert substituents or R1 and R2 form part of a cyclic structure together with the carbon atom to which they are attached. Isononadiene (2,6-dimethyl-1,5-heptadiene) and/or 2,6,10-trimethyl-1,5,9-undecatriene can be obtained by reacting cis-1,4-polyisoprene with isobutene in the presence of a heterogeneous disproportionation catalyst.
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- THE FORMATION AND SUBSEQUENT CYCLISATION OF NOVEL HYDROPEROXIDES FROM A 1,4- AND A 1,5-DIENE
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The preparation of the unsaturated hydroperoxides(3,4,5,6 and 7) by the sensitized photo-oxidation of the 1,4-diene(1) and the 1,5-diene(2) is described, together with the attempted free-radical cyclisation of these.
- Carless, Howard A.J.,Batten, Richard J.
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p. 4735 - 4738
(2007/10/02)
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- Studies on the Conversions of Diols and Cyclic Ethers. Dehydration of Alcohols and Diols on the Action of Dimethylsulfoxide
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The transformations of 13 alcohols and 13 diols in the presence of a small amount dimethylsulfoxide (1/16 mol) were studied.Relationships were found between the type of the hydroxy compound and the selectivity of the transformation, and conclusions were drawn regarding the transformation mechanism.The ether formation observed with certain alcohols proceeds via a carbenium cation.The reaction conditions applied were found suitable for including water elimination from the ditertiary 1,2- and 1,3-diols (pinacol rearrangement, 1,2-elimination).From the 1,4- and 1,5-diols the corresponding oxacycloalkanes can be obtained in good yield.Cyclodehydration occurs by intramolecular nucleophilic substitution, via a concerted mechanism.The effect of DMSO is excerted directly, and proton-catalysis occurs simultaneously.
- Molnar, Arpad,Bartok, Mihaly
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p. 389 - 398
(2007/10/02)
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- Copper(I)-Mediated Synthesis of cis-Isoprenoids. Models for Natural Rubber
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Two copper(I)-mediated routes for the preparation of all-cis-2,6,10-trimethyl-2,6,10-dodecatriene are investigated.Reaction of the Grignard reagent derived from 1-bromo-4-methylpent-3-ene with CuBr, and then with excess propyne, gave a vinylcopper intermediate which could be alkylated with 1-iodo-3-methylpent-3-ene, to afford the required triene stereospecifically cis- in 28percent yield.Iodination of the same intermediate and subsequent conversion to 1-bromo-4,8-dimethyl-3,7-nonadiene is shown to occur with retention of configuration, so allowing the iterative construction of cis-isoprenoids.This vinylcopper-based route is shown to be also applicable to the synthesis of larger cis-isoprenoids.In contrast, the CuI-modified coupling reaction of the Grignard reagent from 1-chloro-2-methylbut-2-ene with neryl chloride gave a mixture of triene isomers.
- Parr, William J. E.
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p. 4101 - 4130
(2007/10/02)
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- Syntheses of 2,6-Dimethyl-1,5-heptadien-3-ol Acetate, the Pheromone of the Comstock Mealybug Pseudococcus comstocki Kuwana, and Its Analogs
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The Comstock mealybug sex pheromone 2,6-dimethyl-1,5-heptadien-3-ol acetate and three analogs were synthesized and compared with natural material.
- Uchida, Minoru,Nakagawa, Kazuyuki,Negishi, Tsutomu,Asano, Shoji,Mori, Kenji
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p. 369 - 372
(2007/10/02)
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