- Bioavailability of echinacea constituents: Caco-2 monolayers and pharmacokinetics of the alkylamides and caffeic acid conjugates
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Many studies have been done over the years to assess the effectiveness of Echinacea as an immunomodulator. We have assessed the potential bioavailability of alkylamides and caffeic acid conjugates using Caco-2 monolayers and compared it to their actual bioavailability in a Phase I clinical trial. The caffeic acid conjugates permeated poorly through the Caco-2 monolayers. Alkylamides were found to diffuse rapidly through Caco-2 monolayers. Differences in diffusion rates for each alkylamide correlated to structural variations, with saturation and N-terminal methylation contributing to decreases in diffusion rates. Alkylamide diffusion is not affected by the presence of other constituents and the results for a synthetic alkylamide were in line with those for alkylamides found in an ethanolic Echinacea preparation. We examined plasma from healthy volunteers for 12 hours after ingestion of Echinacea tablets manufactured from an ethanolic liquid extract. Caffeic acid conjugates could not be identified in any plasma sample at any time after tablet ingestion. Alkylamides were detected in plasma 20 minutes after tablet ingestion and for each alkylamide, pharmacokinetic profiles were devised. The data are consistent with the dosing regimen of one tablet three times daily and supports their usage as the primary markers for quality Echinacea preparations.
- Matthias, Anita,Penman, Kerry G.,Matovic, Nick J.,Bone, Kerry M.,De Voss, James J.,Lehmann, Reg P.
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- Chemoenzymatic asymmetric total syntheses of antitumor agents (3R,9R,10R)- and (3S,9R,10R)-panaxytriol and (R)- and (S)-falcarinol from Panax ginseng using an enantioconvergent enzyme-triggered cascade reaction
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Total asymmetric synthesis of two components of Panax ginseng showing antitumor activity, i.e., (3R,9R,10R)- and (3S,9R,10R)-Panaxytriol and of both enantiomers of Falcarinol was accomplished. Due to the fact that the synthetic strategy was based on enantioconvergent biotransformations, the occurrence of any undesired stereoisomer was entirely avoided. The absolute configuration of naturally occurring Panaxytriol was confirmed to be (3R,9R,10R) on the basis of optical rotation values. It was shown that enzyme-triggered cascade reactions represent a valuable tool for the synthesis of natural products.
- Mayer, Sandra F.,Steinreiber, Andreas,Orru, Romano V. A.,Faber, Kurt
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Read Online
- Ligand-controlled cobalt-catalyzed remote hydroboration and alkene isomerization of allylic siloxanes
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The Co-catalyzed remote hydroboration and alkene isomerization of allylic siloxanes were realized by a ligand-controlled strategy. The remote hydroboration with dcype provided borylethers, while xantphos favored the formation of silyl enol ethers.
- Huang, Jiaxin,Li, Jie,Yang, Wen,Zhang, Kezhuo,Zhao, Pei,Zhao, Wanxiang
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supporting information
p. 302 - 305
(2022/01/03)
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- CYCLOALKYL-CONTAINING CARBOXYLIC ACIDS AND USES THEREOF
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The present application discloses a compound of formula (I) or a salt thereof: (I) and compositions comprising such compound or salt thereof. The use of such compound, salt thereof or composition comprising same for treating anemia or leukopenia, fibrosis, cancer, hypertension and/or a metabolic condition in a subject is also disclosed.
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Page/Page column 84; 85
(2021/06/26)
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- ANTI-BACTERIAL CALCIUM-DEPENDENT ANTIBIOTIC (CDA) ANALOGS AND METHODS OF TREATING BACTERIAL INFECTIONS
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Provided herein are calcium-dependent antibiotics (CDAs), as a novel therapeutic target for treating bacterial infections. The present invention also relates to pharmaceutical compositions comprising such compounds, and to methods of use thereof for combating bacteria and treating bacterial infections.
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Paragraph 0128; 0130
(2021/10/22)
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- Preparation method of longicorn sex pheromone 2, 3-diketone series compounds and derivatives thereof
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The invention discloses a preparation method of longhorn beetle sex pheromone 2, 3-diketone compounds, which comprises the following steps: by using linear carboxylic acid containing 6, 8 and 10 carbons as a raw material, carrying out carboxylic acid [alpha]- halogenation, elimination, reduction and the like to synthesize a series of 2, 3-diketone compounds, and carrying out reduction and chiral resolution on the structure to obtain a series of [alpha]-hydroxy ketone chiral compounds. The route has the characteristics of safety, easiness in operation, simple post-treatment, high yield and low cost.
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- Convergent Synthesis of Calcium-Dependent Antibiotic CDA3a and Analogues with Improved Antibacterial Activity via Late-Stage Serine Ligation
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A convergent synthesis via the late-stage serine ligation of naturally occurring calcium-dependent antibiotic CDA3a and its analogues has been developed, which allowed us to readily synthesize the analogues with the variation on the lipid tail. Some analogues were found to show 100-500-fold higher antimicrobial activity than the natural compound CDA3a against drug resistant bacteria. This study will enhance our understanding of CDA3a and provide valuable antibacterial lead candidates for further development.
- Blasco, Pilar,Chen, Delin,Chen, Sheng,Li, Xuechen,Po, Kathy Hiu Laam
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supporting information
(2020/06/29)
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- Straightforward chemo- and stereoselective fluorocyclopropanation of allylic alcohols: Exploiting the electrophilic nature of the not so elusive fluoroiodomethyllithium
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An unprecedented direct fluorocyclopropanation of allylic alcohols is reported. This simple method involves the not so elusive fluoroiodomethyllithium, a carbenoidic intermediate that under the developed conditions discloses its electrophilic nature. Gratifyingly, the reaction turned out to be highly chemo- and stereoselective, and DFT calculations provided insights into the structure and nature of this new type of carbenoid.
- Colella, Marco,Tota, Arianna,Gro?johann, Angela,Carlucci, Claudia,Aramini, Andrea,Sheikh, Nadeem S.,Degennaro, Leonardo,Luisi, Renzo
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supporting information
p. 8430 - 8433
(2019/07/22)
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- Synthesis of α,β-unsaturated aldehydes as potential substrates for bacterial luciferases
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Bacterial luciferase catalyzes the monooxygenation of long-chain aldehydes such as tetradecanal to the corresponding acid accompanied by light emission with a maximum at 490?nm. In this study even numbered aldehydes with eight, ten, twelve and fourteen carbon atoms were compared with analogs having a double bond at the α,β-position. These α,β-unsaturated aldehydes were synthesized in three steps and were examined as potential substrates in vitro. The luciferase of Photobacterium leiognathi was found to convert these analogs and showed a reduced but significant bioluminescence activity compared to tetradecanal. This study showed the trend that aldehydes, both saturated and unsaturated, with longer chain lengths had higher activity in terms of bioluminescence than shorter chain lengths. The maximal light intensity of (E)-tetradec-2-enal was approximately half with luciferase of P. leiognathi, compared to tetradecanal. Luciferases of Vibrio harveyi and Aliivibrio fisheri accepted these newly synthesized substrates but light emission dropped drastically compared to saturated aldehydes. The onset and the decay rate of bioluminescence were much slower, when using unsaturated substrates, indicating a kinetic effect. As a result the duration of the light emission is doubled. These results suggest that the substrate scope of bacterial luciferases is broader than previously reported.
- Brodl, Eveline,Ivkovic, Jakov,Tabib, Chaitanya R.,Breinbauer, Rolf,Macheroux, Peter
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p. 1487 - 1495
(2017/02/18)
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- Ketenimines from Isocyanides and Allyl Carbonates: Palladium-Catalyzed Synthesis of β,γ-Unsaturated Amides and Tetrazoles
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The reaction of allyl ethyl carbonates with isocyanides in the presence of a catalytic amount of Pd(OAc)2provided ketenimines through β-hydride elimination of the allyl imidoylpalladium intermediates. The insertion of the isocyanide into the π-allyl Pd complex proceeded via an unusual η1-allyl Pd species. The resulting ketenimines were hydrolyzed to β,γ-unsaturated carboxamides during purification by flash column chromatography on silica gel or converted in situ into 1,5-disubstituted tetrazoles by [3+2] cycloaddition with hydrazoic acid or trimethylsilyl azide.
- Qiu, Guanyinsheng,Mamboury, Mathias,Wang, Qian,Zhu, Jieping
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supporting information
p. 15377 - 15381
(2016/12/06)
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- Total synthesis of panaxydol and its stereoisomers as potential anticancer agents
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An efficient total synthesis of natural panaxydol 1a and its seven stereoisomers 1b-h was accomplished; four diastereomers of the natural form were prepared for the first time. Our strategy involves the Cadiot-Chodkiewicz cross-coupling reaction of chiral terminal alkynes with bromoalkynes, the asymmetric alkynylation of aldehydes, and the enantioselective Sharpless epoxidation of allylic alcohols. Preliminary in vitro cytotoxicity evaluation indicated that some synthetic panaxydols possess anticancer activities, and (3S,9R,10S)-panaxydol 1e showed a particularly promising cytotoxic effect.
- Mao, Jianyou,Li, Shuoning,Zhong, Jiangchun,Wang, Bo,Jin, Jing,Gao, Zidong,Yang, Hanze,Bian, Qinghua
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- Simple and expeditious pinacol coupling of non usual α,β-unsaturated carbonyl compounds in water
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Using zinc (0) in a 5% v AcOH aqueous solution allowed the efficient pinacol coupling of aliphatic or aromatic unusual, α,β-unsaturated carbonyl compounds such as citral A in good to excellent yields (56-99%). It can also be successfully applied to acetophenone.
- Billamboz, Muriel,Sotto, Nicolas,Chevrin-Villette, Carole,Len, Christophe
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p. 46026 - 46030
(2015/06/08)
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- Total Synthesis of the Nonenolide Xyolide Using a Regioselective Nucleophilic Epoxide Opening Approach
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The total synthesis of the nonenolide xyolide is described as a convergent synthesis in 16 steps from the commercially available starting material butane-1,4-diol. The key reactions involved are: Sharpless asymmetric epoxidation, Pinnick oxidation, acid-mediated nucleophilic regioselective epoxide ring opening, Steglich esterification, and ring-closing metathesis.
- Wadavrao, Sachin B.,Ghogare, Ramesh S.,Narsaiah, A. Venkat
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p. 2129 - 2137
(2015/07/15)
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- Selective Pinacol Coupling on Regeneratable Supported Acids in Sole Water
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Efficient pinacol coupling was developed in sole water, using a reusable heterogeneous supported acid source and zinc as cheap available metal source. This medium can be easily regenerated up to 10-fold without loss of activity. Moreover, supported acids enhance the selectivity of the pinacol coupling reaction compared with homogeneous acids.
- Sotto, Nicolas,Billamboz, Muriel,Chevrin-Villette, Carole,Len, Christophe
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p. 6375 - 6380
(2015/06/30)
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- Selective transformations of carbonyl functions in the presence of α,β-unsaturated ketones: Concise asymmetric total synthesis of decytospolides A and B
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Enones selectively react with a combination of PPh3 and TMSOTf to produce phosphonium silyl enol ethers, which work as protective groups of enones during the reduction of other carbonyl functions and can be easily deprotected to regenerate parent enones at workup. Furthermore, the first ketone selective alkylations in the presence of enones were also accomplished. This in situ protection method was applied to concise asymmetric total syntheses of decytospolides A and B.
- Yahata, Kenzo,Minami, Masaki,Watanabe, Kei,Fujioka, Hiromichi
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supporting information
p. 3680 - 3683
(2014/08/05)
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- General and highly efficient iron-catalyzed hydrogenation of aldehydes, ketones, and α,β-unsaturated aldehydes
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EnvIRONmentally friendly: The title hydrogenation of aldehydes, ketones, and α,β-unsaturated aldehydes is reported. In the presence of the catalyst 1, primary, secondary, and allylic alcohols were obtained in good to excellent yields under mild reaction conditions. The catalyst is easily and inexpensively prepared, and is also stable to air, water, and column chromatography. Copyright
- Fleischer, Steffen,Zhou, Shaolin,Junge, Kathrin,Beller, Matthias
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p. 5120 - 5124
(2013/06/27)
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- A molecularly defined iron-catalyst for the selective hydrogenation of α,β-unsaturated aldehydes
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A selective iron-based catalyst system for the hydrogenation of α,β-unsaturated aldehydes to allylic alcohols is presented. Applying the defined iron-tetraphos complex [FeF(L)][BF4] (L=P(PhPPh 2)3) in the presence of trifluoroacetic acid a broad range of aldehydes are reduced in high yields using low catalyst loadings (0.05-1 mol %). Excellent chemoselectivity for the reduction of aldehydes in the presence of other reducible moieties, for example, ketones, olefins, esters, etc. is achieved. Based on the in situ detected hydride species [FeH(H 2)(L)]+ a catalytic cycle is proposed that is supported by computational calculations. Copyright
- Wienh?fer, Gerrit,Westerhaus, Felix A.,Junge, Kathrin,Ludwig, Ralf,Beller, Matthias
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supporting information
p. 7701 - 7707
(2013/07/11)
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- Rabbit 3-hydroxyhexobarbital dehydrogenase is a NADPH-preferring reductase with broad substrate specificity for ketosteroids, prostaglandin D2, and other endogenous and xenobiotic carbonyl compounds
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3-Hydroxyhexobarbital dehydrogenase (3HBD) catalyzes NAD(P) +-linked oxidation of 3-hydroxyhexobarbital into 3-oxohexobarbital. The enzyme has been thought to act as a dehydrogenase for xenobiotic alcohols and some hydroxysteroids, but its physiological function remains unknown. We have purified rabbit 3HBD, isolated its cDNA, and examined its specificity for coenzymes and substrates, reaction directionality and tissue distribution. 3HBD is a member (AKR1C29) of the aldo-keto reductase (AKR) superfamily, and exhibited high preference for NADP(H) over NAD(H) at a physiological pH of 7.4. In the NADPH-linked reduction, 3HBD showed broad substrate specificity for a variety of quinones, ketones and aldehydes, including 3-, 17- and 20-ketosteroids and prostaglandin D2, which were converted to 3α-, 17β- and 20α-hydroxysteroids and 9α,11β- prostaglandin F2, respectively. Especially, α-diketones (such as isatin and diacetyl) and lipid peroxidation-derived aldehydes (such as 4-oxo- and 4-hydroxy-2-nonenals) were excellent substrates showing low Km values (0.1-5.9 μM). In 3HBD-overexpressed cells, 3-oxohexobarbital and 5β-androstan-3α-ol-17-one were metabolized into 3-hydroxyhexobarbital and 5β-androstane-3α,17β-diol, respectively, but the reverse reactions did not proceed. The overexpression of the enzyme in the cells decreased the cytotoxicity of 4-oxo-2-nonenal. The mRNA for 3HBD was ubiquitously expressed in rabbit tissues. The results suggest that 3HBD is an NADPH-preferring reductase, and plays roles in the metabolisms of steroids, prostaglandin D2, carbohydrates and xenobiotics, as well as a defense system, protecting against reactive carbonyl compounds.
- Endo, Satoshi,Matsunaga, Toshiyuki,Matsumoto, Atsuko,Arai, Yuki,Ohno, Satoshi,El-Kabbani, Ossama,Tajima, Kazuo,Bunai, Yasuo,Yamano, Shigeru,Hara, Akira,Kitade, Yukio
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p. 1366 - 1375
(2013/11/19)
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- Novel malyngamide structural analogs: Synthesis and biological evaluation
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In the course of our search for new anticancer agents, a series of novel malyngamide derivatives were synthesized by sharpless asymmetric epoxidation, followed by Julia-Kocinski olefination reactions as key reaction sequence. Anticancer activities of all these derivatives were screened against IMR-32, SF-295, SKNSH, HeLa, Colon-502713, SW-620, and Hop-62 cell lines for the first time.
- Reddy, G. Venkateswar,Kumar, T. Vijaya,Siva,Babu, K. Suresh,Srinivas,Sehar, Irum,Saxena,Rao, J. Madhusudana
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p. 4581 - 4591
(2013/09/23)
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- Polyunsaturated alkyl amides from echinacea: Synthesis of diynes, enynes, and dienes
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The synthesis of 20 alkyl amides, including 15 naturally occurring polyunsaturated alkyl amides previously identified from Echinacea spp. (1-13 and 62) or from Achilla sp. (55) and five previously unknown geometric isomers (23, 28, 67, 73, and 80), is described. Importantly, these amides include all of the major alkyl amides present in commercially used Echinacea extracts. The syntheses demonstrate methodology used for constructing alkyl amides containing conjugated diyne and isomerically pure enyne and diene moieties and may be adapted easily for the preparation of other alkyl amides present in Echinacea spp. Terminal-conjugated diynes were prepared by a Cadiot-Chodkiewitz coupling/deprotection sequence utilizing a protected bromoacetylene, and methyl-substituted diynes were made via a base-catalyzed rearrangement of terminal-skipped diynes. Conjugated dienes were prepared conveniently and with high stereoselectivity by the reduction of enynes or diynes with Rieke zinc. With the exception of 1-2 and 11-12, the alkyl amides are synthesized here for the first time, and their NMR data are consistent with that of the reported isolated natural compounds.
- Matovic, Nicholas J.,Hayes, Patricia Y.,Penman, Kerry,Lehmann, Reginald P.,De Voss, James J.
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experimental part
p. 4467 - 4481
(2011/07/30)
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- A facile method for the rapid and selective deprotection of methoxymethyl (MOM) ethers
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We describe a rapid and efficient method for selective deprotection of methoxymethyl (MOM) ethers using ZnBr2 and n-PrSH, which completely removed MOM from diverse MOM ethers of primary, secondary, and tertiary alcohols or phenol derivatives. The deprotection takes less than ten minutes with both high yield and selectivity in the presence of other protecting groups. In addition, the rapid deprotection of MOM ethers of tertiary hydroxyls in high yield with no epimerization allows MOM to be a suitable protecting group for tertiary alcohols.
- Han, Jae Hyun,Kwon, Young Eun,Sohn, Jeong-Hun,Ryu, Do Hyun
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experimental part
p. 1673 - 1677
(2010/04/04)
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- Asymmetric synthesis of panaxydol and its stereoisomers
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A facile synthesis of four possible stereoisomers of panaxydol was described. The configurations of C-3 and C-9, C-10 positions were established by enantioselective enantio selective reduction and Sharpless asymmetric dihydroxylation, respectively.
- Yu, Hsi-Jung,Sun, Chang-Ming,Chen, Chien-Chih,Wu, Tsao-Chin,Wei, Chia-Ling,Shen, Chien-Chang
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p. 857 - 868
(2007/10/03)
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- Stereoselective Total Synthesis of (+)-Virol C
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A highly stereoselective synthesis of (+)-Virol C (1) has been achieved starting from octan-1-ol (6) using two different strategies, elimination reactions of epoxyallyl chloride 12 and epoxy chloride 16 to hydroxyenyne 2 and trans-hydroxyalkenyl chloride 4 as key reactions in route a and route b, respectively.
- Sabitha, Gowravaram,Reddy, Ch. Srinivas,Srihari, Pabbaraja,Yadav, Jhillu Singh
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p. 2699 - 2704
(2007/10/03)
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- A simple synthetic method for chiral 1,2-epoxides and the total synthesis of a chiral pheromone epoxide
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Chiral 1,2-epoxyalkan-3-ol tosyl esters 4a-h were successfully synthesized from alkynols or allyl chlorides in three steps using Sharpless AD reaction as a key step in good yields. The chiral insect pheromone epoxide (6Z,9S,10R)-9,10-epoxyhenicos-6-ene 9 was thus smoothly synthesized from the corresponding key intermediate 4g.
- Zhang, Zhi-Bo,Wang, Zhi-Min,Wang, Yu-Xiu,Liu, Huan-Quan,Lei, Gui-Xin,Shi, Min
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- Chemical defense in the stink bug Cosmopepla bimaculata
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Adult Cosmopepla bimaculata discharge a volatile secretion from paired ventral metathoracic glands (MTG) when disturbed. Collected volatiles were similar in both sexes and consisted of n-tridecane (67%), (E)-2-decenal (12%), (E)-2-decenyl acetate (12%), (E)-2-hexenal (3%), hexyl acetate (2%), n-dodecane (2%), a tridecene isomer (1%), and n-undecane, n-tetradecane, and n-pentadecane (all 1%). In addition, undisturbed males produced a novel insect compound, (E)-8-heneicosene, whose function is unknown. The MTG secretion emerges as an enlarging droplet, which is held in place by a cuticular projection and a pleural scent area consisting of specialized rough cuticle surrounding the gland opening. Insects can selectively discharge from either the right or left gland or both glands simultaneously, can control the amount of fluid ejected, and can resorb the ejected secretion droplet back into the gland reservoir, in feeding trials, killdeer (Charadrius vociferus), starlings (Sturnus vulgaris), robins (Turdus migratorius), and anole lizards (Anolis carolinensis) rejected or demonstrated aversion to feeding on the bugs. Furthermore, bugs that lacked the secretion were more susceptible to predation than bugs with secretion, suggesting that the secretion functions in defense against predators.
- Krall, Bryan S.,Bartelt, Robert J.,Lewis, Cara J.,Whitman, Douglas W.
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p. 2477 - 2494
(2007/10/03)
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- A facile synthetic method for chiral 1,2-epoxides and the total synthesis of chiral pheromone epoxides
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Chiral 1,2-epoxy-3-alkanol tosylates were successfully synthesized from alkynols in three steps using the Sharpless AD reaction as a key step in good yields. Two chiral insect pheromone epoxides were smoothly obtained from the corresponding key intermediate.
- Zhang, Zhi-Bo,Wang, Zhi-Min,Wang, Yu-Xiu,Liu, Huan-Quan,Lei, Gui-Xin,Shi, Min
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p. 837 - 840
(2007/10/03)
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- Ring opening of 2,3-epoxy 1-tosylates to halohydrins and subsequent elaboration to asymmetrical alcohols
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2,3-epoxy alcohols-1-tosylates are regio and chemoselectively opened to the corresponding 3-halohydrins (I, Br, Cl): the reduction of the iodohydrins to the monoprotected diols and subsequent standard coupling of the tosyl group leads to a straightforward synthesis of optically active naturally occurring pheromones
- Federici,Federici, Chiara,Righi,Righi, Giuliana,Rossi,Rossi, Leucio,Bonini,Bonini, Carlo,Chiummiento,Chiummiento, Lucia,Funicello,Funicello, Maria
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p. 797 - 800
(2007/10/02)
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- Syntheses of cerulenin and its analogs. I. Cerulenin and its analogs with modified side chain
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Optically active cerulenin 1, a potent inhibitor of fatty acid synthetase, was prepared via the condensation of the epoxy aldehyde 8 and the alkenyl lithium 16. In order to evaluate the effects of (E,E)-1,4-double bonds of the cerulenin side chain on the interaction with the enzyme, a series of optically active cerulenin analogs 32a-i with modified side chains and tetrahydrocerulenin 3 were synthesized by similar procedures.
- Morisaki,Funabashi,Furukawa,Shimazawa,Kanematsu,Ando,Okuda,Iwasaki
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p. 2945 - 2953
(2007/10/02)
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- A New Route to Epoxides and Ketones by m-Chloroperbenzoic Acid Oxidation of β-Hydroxyalkyl Phenyl Selenides and Tellurides
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Treatment of primary (β-hydroxy)alkyl phenyl selenides with m-chloroperbenzoic acid (3-5 mol equiv.) in tetrahydrofuran or methanol gives the corresponding epoxides in high yield. cis-1-Methylene-4-t-butylcyclohexane oxide is obtained stereospecifically from 4-t-butyl-1-(phenylselenomethyl)cyclohexanol prepared by the addition of α-(phenylseleno)methyl anion to 4-t-butylcyclohexanone.On the other hand, similar oxidation of secondary (β-hydroxy)alkyl phenyl selenides affords the unexpected carboxylic acids or their esters.When a phenyl group is present on the carbon bearing the OH moiety in β-hydroxyselenides and tellurides , the oxidation is accompanied by phenyl migration to afford ketones.The reaction can be applied to one-carbon-homologated ring expansion of the benzene-ring-fused cyclic ketones by combining with the addition of an α-(phenylseleno)methyl or α-(phenyltelluro)methyl moiety to the ketones.
- Uemura, Sakae,Ohe, Kouichi,Sugita, Nobuyuki
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p. 1697 - 1703
(2007/10/02)
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- Asymmetric Synthesis Using Tartrate Ester Modified Allylboronates. 1. Factors Influencing Stereoselectivity
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A detailed study of the factors that influence the enantio- and diastereoselectivity of the reactions of tartrate allylboronate 1 with chiral and achiral aldehydes is reported.The stereoselectivity of these reactions is sensitive to variables such as reaction temperature (best results invariably are obtained at -78 deg C), solvent (toluene is best for aliphatic aldehydes; THF is preferred for aromatic aldehydes), and moisture (use of molecular sieves is recommended to maintain an anhydrous reaction environment), but not on the structure of the tartrate ester.Tartrate allylboronate 1 has been found to be exceptionally reactive compared to other, previously studied allylboronates, and even the reactions of very hindered substrates (e.g., pivalaldehyde) are complete within several hours at -78 deg C.An improved method for synthesis of 1 is described that involves the reaction of allylmagnesium bromide with (iPrO)3B followed by aqueous hydrolysis and esterification with DIPT.Yields of 1 are considerably higher (65-76percent) by using this new procedure, and the crude reagent so prepared may be used directly in allylboration experiments.A simple method for standardizing solutions of 1 is described.Finally, the absolute stereochemistry of five homoallylic alcohols (5a-e) were assigned by correlation with epoxy alcohols prepared via the Sharpless asymmetric epoxidation.The results of these correlations are in complete agreement with the stereochemical picture presented in our 1985 publication.
- Roush, William R.,Hoong, Lee K.,Palmer, Michelle A. J.,Park, Jae Chan
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p. 4109 - 4117
(2007/10/02)
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- The Synthesis and Ring Opening Reactions of 1,10-Disubstituted-2,3 (R,R + S,S) Epoxy Decanes - A Route to Heterocyclic Prostaglandin Analogues.
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Synthetic routes leading to (E)-1,10-di-derivatised dec-2-enes are outlined; in particular the syntheses of (E)-1-benzyloxy-10-methoxyethoxymethoxydec-2-ene and (E)-10-benzyloxy-1-methoxyethoxymethoxydec-2-ene are described.Ring opening reactions between 2-lithio-1,3-dithiane and the oxiranes derived from the above two decenes were studied and the ratio of isomeric dithianyl alcohols produced was shown to be influenced by the nature of the C-1 hydroxyl protecting group.These results are discussed in terms of co-ordinative interactions between the lithiodithiane reagent and the complementary oxygens of the substituted oxiranes.
- Grayshan, Roger,Keal, Colin A.,Sackville, Michael A.
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p. 2501 - 2542
(2007/10/02)
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- Synthesis of the optical antipodes of 4-alkyl-γ-lactones
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Optical antipodes of 4-alkyl-γ-lactones 3 have been prepared by photochemical rearrangement of optically active α,β-epoxy diazomethyl ketones 1 in ethanol to give 4-hydroxy-alkenoates 2, followed by reduction of the alkene bond and subsequent lactonization.The required epoxy diazomethyl ketones 1 were obtained via the following sequence of reactions: alkylation of 2-propyn-1-ol, subsequent reduction to the alkenols 6, Sharpless epoxidation to 2,3-epoxy alcohols 7, oxidation to glycidic esters 8 and finally conversion to diazo ketones 1.The enantiomeric purities range from 84 to 100percent.
- Thijs, Lambertus,Waanders, Peter P.,Stokkingreef, Edwin H. M.,Zwanenburg, Binne
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p. 332 - 337
(2007/10/02)
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- Syntheses of Acetates of 2(E)-Hexenol, 2(E)-Octenol and 2(E)-Decenol
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The sex attractants 2(E)-hexenol acetate (I), 2(E)-octenol acetate (II) and 2(E)-decenol acetate (III) have been synthesized.Selective C-alkylation of propargyl alcohol with n-propyl, n-pentyl and n-heptyl bromides furnishes the corresponding alkynes (IV, VI and VIII).Reduction of acetylenic bonds in IV, VI and VIII with LAH and subsequent acetylation afford the title compounds.
- Vig, O. P.,Jindal, R. T.
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p. 919 - 920
(2007/10/02)
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