- Total Synthesis and Structure Revision of Boholamide A
-
The 15-membered cyclic depsipeptide boholamide A and an epimer were prepared by total synthesis for the first time, thus leading to a revision of C6 stereochemistry in the originally proposed structure of natural boholamide A. This convergent route features achievement of a macro-lactamization step in a gram scale. The revised boholamide A was sythesized with 16 linear steps in 5.46% overall yield. This work facilitates the investigations of boholamide A as a potential hypoxia-selective anticancer agent.
- Han, Fangzhi,Liu, Guangju,Zhang, Xuhai,Ding, Yahui,Wang, Liang,Wu, Yijing,Chen, Yue,Zhang, Quan
-
supporting information
p. 4976 - 4980
(2021/06/30)
-
- A Specific Blend of Drakolide and Hydroxymethylpyrazines: An Unusual Pollinator Sexual Attractant Used by the Endangered Orchid Drakaea micrantha
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Bioactive natural products underpin the intriguing pollination strategy used by sexually deceptive orchids. These compounds, which mimic the sex pheromones of the female insect, are emitted in particular blends to lure male insect pollinators of specific species. By combining methods from field biology, analytical chemistry, electrophysiology, crystallography, and organic synthesis, we report that an undescribed β-hydroxylactone, in combination with two specific hydroxymethylpyrazines, act as pollinator attractants in the rare hammer orchid Drakaea micrantha. This discovery represents an unusual case of chemically unrelated compounds being used together as a sexual attractant. Furthermore, this is the first example of the identification of pollinator attractants in an endangered orchid, enabling the use of chemistry in orchid conservation. Our synthetic blend is now available to be used in pollinator surveys to locate suitable sites for plant conservation translocations.
- Bohman, Bj?rn,Tan, Monica M. Y.,Phillips, Ryan D.,Scaffidi, Adrian,Sobolev, Alexandre N.,Moggach, Stephen A.,Flematti, Gavin R.,Peakall, Rod
-
supporting information
p. 1124 - 1128
(2019/12/24)
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- Enantioselective Synthesis of the Proposed Structure of Santinol D
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In connection with structural verification of santinol D, a unique tricylglycerol isolated from Helichrysum italicum subsp. microphyllum, four possible isomers of its C-2'''and C-4''' centers were synthesized. The two enolizable chiral centers were installed with pre-defined absolute configurations using Evans alkylation and aldol condensation, respectively. The extra chiral center introduced in the aldol condensation was removed by Dess–Martin oxidation to convert the adjacent methine group into the highly enolizable subunit of an α-alkyl-β-keto ester at the end of the synthesis. The synthetic isomers provided unequivocal physical and NMR data for every single enantiomer and thus provided the information required for the configurational assignment of this natural product. With the aid of a model compound, the racemization of such species was examined polarimetrically under several sets of typical conditions and the rates were also calculated from the corresponding kinetics data.
- Xiong, Xin,Wu, Yikang,Liu, Bo
-
p. 948 - 960
(2020/02/15)
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- Desymmetrization of C2-Symmetric Bis(Boronic Esters) by Zweifel Olefinations
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anti-Configured 1,3-dimethyl deoxypropionate motifs are important sub structures in natural products. Herein, we describe a bidirectional approach for the rapid construction of natural products featuring such motifs by using C2-symmetrical 1,3-bis(boronic esters). As for its application in convergent syntheses it was important to establish a selective mono-Zweifel olefination we describe the scope and limitations by using different 1,3-bis(boronic esters) and nucleophiles. This protocol takes advantage of the combination of the Hoppe–Matteson–Zweifel chemistry, which was elegantly put into practice by Aggarwal et al. In order to show its applicability the total syntheses of two natural products, serricornin and (+)-invictolide, were performed.
- Linne, Yannick,Sch?nwald, Axel,Wei?bach, Sebastian,Kalesse, Markus
-
supporting information
p. 7998 - 8002
(2020/06/09)
-
- Synthesis and fungicidal activity of 2-methylalkyl isonicotinates and nicotinates
-
Abstract: Homologs and analogs of 2-methylheptyl isonicotinate (new, natural antifungal and antibacterial antibiotic isolated from Streptomyces sp. 201): racemic 2-methylalkyl isonicotinates 4 and nicotinates 5 and enantiomerically enriched in the R and S isomers, 2-methylpentyl isonicotinate and nicotinate were obtained. Fungistatic activity of the compounds was evaluated. Nicotinates 5a–c show significant activity against phytopathogenic fungi: Fusarium culmorum, Phytophthora cactorum, Rhizoctonia solani. The activity of the enantiomerically enriched compounds was comparable to the activity of racemic ones. There was no significant difference in fungistatic activity between the enantiomerically enriched R and S isomers. Investigated compounds and their oxalates have proven to be active against chalkbrood disease caused by fungal species Ascosphaera apis. The activity of the nicotinates 5a and 5b and oxalates 5a–c against Ascosphaera apis was higher than the activity of oxalic acid itself. Especially high activity was shown for 2-methylbutyl nicotinate 5a and oxalate of 2-methylpentyl nicotinate 5b. Graphical abstract: [InlineMediaObject not available: see fulltext.]
- Huras, Bogumi?a,Zakrzewski, Jerzy,Krawczyk, Maria,Bombińska, Danuta,Cieniecka-Ros?onkiewicz, Anna,Michalczyk, Alicja
-
p. 509 - 517
(2017/02/15)
-
- Asymmetric hydrogenation of allylic alcohols using ir?N,P-Complexes
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In this study, a series of γ,γ-disubstituted and β,γ-disubstituted allylic alcohols were prepared and successfully hydrogenated using suitable N,P-based Ir complexes. High yields and excellent enantioselectivities were obtained for most of the substrates studied. This investigation also revealed the effect of the acidity of the N,P?Ir-complexes on the acid-sensitive allylic alcohols. DFT ΔpKa calculations were used to explain the effect of the N,P-ligand on the acidity of the corresponding Ir-complex. The selectivity model of the reaction was used to accurately predict the absolute configuration of the hydrogenated alcohols.
- Li, Jia-Qi,Liu, Jianguo,Krajangsri, Suppachai,Chumnanvej, Napasawan,Singh, Thishana,Andersson, Pher G.
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p. 8342 - 8349
(2018/05/23)
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- PROCESSES FOR THE SYNTHESIS OF CHIRAL 1-ALKANOLS
-
The invention relates to highly enantioselective processes for the synthesis of chiral 1-alkanols via Zr-catalyzed asymmetric carboalumination of alkenes.
- -
-
Paragraph 0214; 0215; 0222; 0223
(2016/12/01)
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- Direct Generation of Triketide Stereopolyads via Merged Redox-Construction Events: Total Synthesis of (+)-Zincophorin Methyl Ester
-
(+)-Zincophorin methyl ester is prepared in 13 steps (longest linear sequence). A bidirectional redox-triggered double anti-crotylation of 2-methyl-1,3-propane diol directly assembles the triketide stereopolyad spanning C4-C12, significantly enhancing step economy and enabling construction of (+)-zincophorin methyl ester in nearly half the steps previously required.
- Kasun, Zachary A.,Gao, Xin,Lipinski, Radoslaw M.,Krische, Michael J.
-
supporting information
p. 8900 - 8903
(2015/08/03)
-
- PROCESSES FOR THE SYNTHESIS OF CHIRAL 1-ALKANOLS
-
The invention relates to highly enantioselective processes for the synthesis of chiral 1-alkanols via Zr-catalyzed asymmetric carboalumination of alkenes.
- -
-
Paragraph 00110; 00114
(2015/07/23)
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- Widely applicable synthesis of enantiomerically pure tertiary alkyl-containing 1-alkanols by zirconium-catalyzed asymmetric carboalumination of alkenes and palladium- or copper-catalyzed cross-coupling
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A highly enantioselective and widely applicable method for the synthesis of various chiral 2-alkyl-1-alkanols, especially those of feeble chirality, has been developed. It consists of zirconium-catalyzed asymmetric carboalumination of alkenes (ZACA), lipase-catalyzed acetylation, and palladium- or copper-catalyzed cross-coupling. By virtue of the high selectivity factor (E) associated with iodine, either (S)- or (R)-enantiomer of 3-iodo-2-alkyl-1- alkanols (1), prepared by ZACA reaction of allyl alcohol, can be readily purified to the level of ≥99 % ee by lipase-catalyzed acetylation. A variety of chiral tertiary alkyl-containing alcohols, including those that have been otherwise difficult to prepare, can now be synthesized in high enantiomeric purity by Pd- or Cu-catalyzed cross-coupling of (S)-1 or (R)-2 for introduction of various primary, secondary, and tertiary carbon groups with retention of all carbon skeletal features. These chiral tertiary alkyl-containing alcohols can be further converted into the corresponding acids with full retention of the stereochemistry. The synthetic utility of this method has been demonstrated in the highly enantioselective (≥99 % ee) and efficient syntheses of (R)-2-methyl-1-butanol and (R)- and (S)-arundic acids. Look, mom, one hand! 2-Alkyl-1-alkanols of feeble chirality have been synthesized by a sequence of zirconium-catalyzed asymmetric carboalumination of alkenes (ZACA), lipase-catalyzed acetylation, and Pd- or Cu-catalyzed cross-coupling in high enantiomeric purity of ≥99 % ee. The synthetic utility of this method has been demonstrated in highly enantioselective and efficient syntheses of (R)-2-methyl-1-butanol, (R)- and (S)-arundic acids. Copyright
- Xu, Shiqing,Lee, Ching-Tien,Wang, Guangwei,Negishi, Ei-Ichi
-
p. 1829 - 1835
(2013/09/02)
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- Tumescenamide C, an antimicrobial cyclic lipodepsipeptide from Streptomyces sp.
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Tumescenamide C, a new cyclic lipodepsipeptide, was isolated from a culture broth of an actinomycete Streptomyces sp. KUSC-F05. Tumescenamide C was a congener of tumescenamides A and B, representing a sixteen-membered ring system, consisting of two proteinogenic and three non-proteinogenic amino acids, to which a methyl-branched fatty acid was attached. The planar structure was determined by spectroscopic analysis, while its absolute stereochemistry was determined by chemical degradation and asymmetric synthesis. Tumescenamide C exhibited antimicrobial activity with high selectivity against Streptomyces species.
- Kishimoto, Shinji,Tsunematsu, Yuta,Nishimura, Shinichi,Hayashi, Yutaka,Hattori, Akira,Kakeya, Hideaki
-
experimental part
p. 5572 - 5578
(2012/09/08)
-
- Metathesis-mediated synthesis of (R)-10-Methyl-2-tridecanone, the southern corn rootworm pheromone
-
(R)-10-Methyl-2-tridecanone, the female sex pheromone of the southern corn rootworm (Diabrotica undecimpunctata howardi Barber), was synthesized in 9 steps from methyl (S)-3-hydroxy-2-methylpropanoate in a 15.7% overall yield. Olefin cross metathesis between (R)-6-methyl-1-nonene and 5-hexen-2-one employing Grubbs' first-generation catalyst was the key step of the synthesis.
- Shikichi, Yasumasa,Moriy, Kenji
-
experimental part
p. 407 - 409
(2012/08/13)
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- Highly enantioselective iridium-catalyzed hydrogenation of α,β-unsaturated esters
-
α,β-Unsaturated esters have been employed as substrates in iridium-catalyzed asymmetric hydrogenation. Full conversions and good to excellent enantioselectivities (up to 99 % ee) were obtained for a broad range of substrates with both aromatic- and aliphatic substituents on the prochiral carbon. The hydrogenated products are highly useful as building blocks in the synthesis of a variety of natural products and pharmaceuticals. Asymmetric hydrogenation: A variety of α,β-unsaturated esters were hydrogenated with high enantioselectivities (see scheme). The hydrogenated products have been used in synthetic transformations as well as in formal total syntheses. Copyright
- Li, Jia-Qi,Quan, Xu,Andersson, Pher G.
-
supporting information
p. 10609 - 10616
(2012/11/07)
-
- Chemical development of an α2δ ligand, (3 S,5 R)-3-(Aminomethyl)-5-methyloctanoic acid
-
Three synthetic approaches, suitable for the large scale manufacture of the α2δ-ligand, (3S,5R)-3-(aminomethyl)-5-methyloctanoic acid 3, have been evaluated. The selected seven step manufacturing process has then been optimized and used to deliver over 20 kg of API; salient features of the synthesis include the use of 4,4,4-trimethoxybutyronitrile as an efficient four carbon amino acid equivalent. Highly selective kinetic resolution of the C3 stereocentre was accomplished via diastereoselective hydrolysis of a cyanoester intermediate using Amano Lipase PS-SD. Extensive process optimisation of the route starting from (R)-2-methylpentanol, led to significant improvements through telescoping, with less than 62 kg of solvent being needed to produce 1 kg of API.
- Murtagh, Lorraine,Dunne, Catherine,Gabellone, Gino,Panesar, Niamh J.,Field, Stuart,Reeder, Lisa M.,Saenz, James,Smith, George P.,Kissick, Kyle,Martinez, Carlos,Van Alsten, John G.,Evans, Margaret C.,Franklin, Lloyd C.,Nanninga, Thomas,Wong, John
-
experimental part
p. 1315 - 1327
(2012/01/12)
-
- Iridium-catalyzed asymmetric hydrogenation of unfunctionalized, trialkyl-substituted olefins
-
Chiral iridium complexes with bicyclic pyridine-based N,P ligands have emerged as efficient catalysts for the enantioselective hydrogenation of unfunctionalized trialkyl-substituted olefins. Optimization of the reaction conditions by variation of the solvent, pressure, and temperature led to enantiomeric excesses of up to 99%. Three pure alkenes, (E)-2-cyclohexyl-2- butene and (E)- and (Z)-3,4-dimethyl-2-pentene were converted into the corresponding chiral alkanes with 97%, 94%, and 93% ee, respectively. Hydrogenation of the three C=C bonds of both α- and γ-tocotrienyl acetate led to α- and γ-tocopheryl acetate with very high diastereoselectivity. The same catalysts were successfully applied in the hydrogenation of trisubstituted alkenes with a carboxylic ester or a keto group in the γ position. This reaction was used as a key step in a highly enantioselective synthesis of the pheromone of the caddisfly Hesperophylax occidentalis. The hydrogenation of a structurally analogous allylic alcohol also gave high enantioselectivities. Unfunctionalized trialkyl-substituted olefins are hydrogenated with high efficiency and excellent enantioselectivity using iridium complexes derived from chiral N,P ligands. In this way, pharmaceutically interesting and industrially relevant compounds with chiral alkyl fragments are easily accessible with high diastereo- and enantioselectivities. Copyright
- Wang, Aie,Fraga, Rui P. A.,Hoermann, Esther,Pfaltz, Andreas
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p. 599 - 606
(2011/10/12)
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- Development of a practical biocatalytic process for (R)-2-methylpentanol
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(R)-2-Methylpentanol is an important chiral intermediate for the synthesis of certain medicinally important compounds, natural products, and liquid crystals. Here we describe the development of a practical kinetic resolution utilizing an enantiospecific bio - catalytic reduction of racemic 2-methylvaleraldehyde. The process utilizes an evolved ketoreductase enzyme to selectively reduce the (R)-enantiomer of racemic 2-methylvaleraldehyde to the desired product with high volumetric productivity. A scaleable method for separating the desired product from the off-enantiomer of the starting material is also described. The process is cost-effective, green, and amenable to manufacturing scale.
- Gooding, Owen W.,Voladri, Rama,Bautista, Abigail,Hopkins, Thutam,Huisman, Gjalt,Jenne, Stephan,Ma, Steven,Mundorff, Emily C.,Savile, Megan M.,Truesdell, Susan J.,Wong, John W.
-
experimental part
p. 119 - 126
(2010/04/29)
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- Design, synthesis, and biological activity of isophthalic acid derivatives targeted to the C1 domain of protein kinase C
-
Protein kinase C (PKC) is a widely studied molecular target for the treatment of cancer and other diseases. We have approached the issue of modifying PKC function by targeting the C1 domain in the regulatory region of the enzyme. Using the X-ray crystal structure of the PKC δ C1b domain, we have discovered conveniently synthesizable derivatives of dialkyl 5-(hydroxymethyl)isophthalate that can act as potential C1 domain ligands. Structure-activity studies confirmed that the important functional groups predicted by modeling were indispensable for binding to the C1 domain and that the modifications of these groups diminished binding. The most promising compounds were able to displace radiolabeled phorbol ester ([3H]PDBu) from PKC α and δ at Ki values in the range of 200-900 nM. Furthermore, the active isophthalate derivatives could modify PKC activation in living cells either by inducing PKC-dependent ERK phosphorylation or by inhibiting phorbol-induced ERK phosphorylation. In conclusion, we report here, for the first time, that derivatives of isophthalic acid represent an attractive novel group of C1 domain ligands that can be used as research tools or further modified for potential drug development.
- Af Genn?s, Gustav Boije,Talman, Virpi,Aitio, Olli,Ekokoski, Elina,Finel, Moshe,Tuominen, Raimo K.,Yli-Kauhaluoma, Jari
-
supporting information; scheme or table
p. 3969 - 3981
(2010/01/16)
-
- COMPOUNDS FOR INHIBITING WIP1, PRODRUGS AND COMPOSITIONS THEREOF, AND RELATED METHODS
-
The invention provides compounds useful in inhibiting the activity of a Wip1 protein in a cell as well as prodrugs thereof, related methods of use and compositions which include the aforesaid compounds and prodrugs thereof. The compounds comprise a ring structure having at least five functional groups bonded thereto, wherein each functional group is bonded to a different ring atom, and wherein the at least five functional groups comprise: (a) first (R1) and second (R3) moieties each comprising a phosphate group wherein these first and second moieties are separated by at least one ring atom; (b) first (R2) and second (R4) hydrophobic groups, wherein the first and second hydrophobic groups are separated by at least one ring atom, and wherein the first hydrophobic group is bonded to a ring atom located between the ring atoms to which the first (R1) and second (R2) moieties are bonded; and an amide or carboxylic acid (R5).
- -
-
Page/Page column 39
(2009/04/25)
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- Zirconium-catalyzed asymmetric carboalumination of alkenes: ZACA-lipase-catalyzed acetylation synergy
-
ZACA-lipase-catalyzed acetylation tandem reactions provide highly efficient and selective routes to either (R)- or (S)-2-methyl-1-alkanols, making, for the first time, the ZACA-based asymmetric synthesis of 2-methyl-1-alkanols widely applicable and satisfactory.
- Huang, Zhihong,Tan, Ze,Novak, Tibor,Zhu, Gangguo,Negishi, Ei-Ichi
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p. 539 - 545
(2008/02/08)
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- New chiral synthons for efficient introduction of bispropionates via stereospecific oxonia-cope rearrangements
-
Compounds 1 and 2 are novel synthons for bispropionate synthesis, undergoing stereospecific Lewis acid-catalyzed transfer of the bispropionate unit with a variety of aldehydes, including α-chiral aldehydes. Thus 1 leads to the E-alkene bispropionate 3 with anti-stereochemistry, whereas diastereomer 2 gives the Z-alkene product 4, under mild conditions and with complete stereospecificity. The efficacy of this methodology is demonstrated in a short synthesis of invictolide beginning with 2 and (R)-2-methylpentanal. Copyright
- Chen, Yi-Hung,McDonald, Frank E.
-
p. 4568 - 4569
(2007/10/03)
-
- Total synthesis of a hemiacetal polypropionate from Siphonaria australis
-
A highly stereocontrolled synthesis of (2S,3R,5R,6S)-6-[(1E,3R)-1,3- dimethylhex-1-enyl]-2-ethyl-2-hydroxy-3,5-dimethyltetrahydro-4H-pyran-4-one has been achieved in 13 steps and an overall yield of 7.6% from (A)-(+)-4- benzyloxazolidin-2-one. This substrate-controlled asymmetric synthesis utilized Paterson's lactate-derived chiral ketone (2S)-2-(benzoyloxy) pentan-3-one to generate the 5R and 6S stereocentres and alkylation of an Evans' auxiliary to generate the remote side-chain 3R stereocentre. Furthermore, a novel, highly efficient, and selective strategy was used to generate an enol trimethylsilyl ether whose subsequent Mukaiyama aldol condensation gave the acyclic precursor to the final product. A thermodynamically controlled cyclization then gave (2S,3R,5R,6S)-6-[(1E,3R)-1,3-dimethylhex-1-enyl]-2-ethyl-2-hydroxy-3, 5-dimethyltetrahydro-4H-pyran-4-one with control of the 2S and 3R stereocentres. The NMR spectroscopic data and optical rotation obtained for synthetic (2S,3R,5R,6S)-6-[(1E,3R)-1,3-dimethylhex-1-enyl]-2-ethyl-2-hydroxy-3, 5-dimethyltetrahydro-4H-pyran-4-one were consistent with those reported forthe hemiacetal isolated from Siphonaria australis, and thus, prove the absolute and relative configuration of the natural product.
- Lister, Troy,Perkins, Michael V.
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p. 787 - 797
(2007/10/03)
-
- Regio- and stereochemical study of sex pheromone of pine sawfly; Diprion nipponica
-
Regio- and stereoisomers of 1,2,ω-trimethyldecyl propionate (ω = 5-9) were prepared from stereochemically pure chiral building blocks as sex pheromone candidates of a pine sawfly; Diprion nipponica. Among the synthesized candidates, (1S,2R,8S)-1,2,8-trimethyldecyl propionate was found to be the sex pheromone of D. nipponica, based on compatibility of its GC-MS data with that of the extract of females, and its significantly high pheromone activity in a field bioassay. The field bioassay of the synthesized compounds also revealed that (1S,2R,SR)-1,2,8-trimethyldecyl propionate, (1S,2R,7S)-1,2,7-trimethyldecyl propionate, and (1S,2R,6S)-1,2,6-trimethyldecyl propionate could attract male sawflies to some extent as pheromone mimics.
- Tai, Akira,Syouno, Emi,Tanaka, Kazuki,Fujita, Morifumi,Sugimura, Takashi,Higashiura, Yasutomo,Kakizaki, Masashi,Hara, Hideho,Naito, Tikahiko
-
p. 111 - 121
(2007/10/03)
-
- Structural elucidation of twelve novel esters composed of five fatty acids and three new branched alcohols together with four monoterpenoids from Sancassania shanghaiensis (Acari: Acaridae).
-
A total of 12 novel esters and four monoterpenoids (rosefuran, (2R,3R)-epoxyneral, and alpha- and beta-acaridials) were detected by GC/MS analyses as the opisthonotal gland components of Sancassania shanghaiensis. The acidic fraction after hydrolysis was composed of five common fatty acids (palmitic, stearic, oleic, linoleic and arachidic acid), while the alcoholic fraction consisted of two major components (C6 and C8 alcohols with branched methyls), together with a trace amount of C9 alcohol. The two major alcohols were identified as new alcohols [(S)-2-methylpentanol and (2S,4S)-2,4-dimethylhexanol] by comparing the physico-chemical data of their 3,5-dinitrobenzoates with those of regio-selectively synthesized alcohols. The C9 alcohol was suggested as (2S,4S)-2,4-dimethylheptanol, based on a structural and biogenetic analogy to the C6 and C8 alcohols. Five of the compounds were each identified by GC to be (S)-2-methylpentyl esters from five fatty acids, and the other five components likewise as (2S,4S)-2,4-dimethylhexyl esters. The remaining two were suggested as (2S,4S)-2,4-dimethylheptyl stearate and linolate.
- Sakata,Okabe,Kuwahara
-
p. 919 - 927
(2007/10/03)
-
- Identification and assignment of the absolute configuration of biologically active methyl-branched ketones from limnephilid caddis flies
-
Glands of the 4th and 5th abdominal stemite of the caddis flies Potamophylax latipennis, Potamophylax cingulatus, and Glyphotaelius pellucidus contain (S)-4-methyl-3-heptanone (4a), (4S,6S)-4,6-dimethyl-3-octanone (4b), and (4S,6S)-4,6-dimethyl-3-nonanone (4c). As shown by gas chromatography coupled with electrophysiological recordings, these ketones elicit a strong response in the insects' antennae. The structural assignment of the compounds was achieved on the basis of mass spectra, enantioselective synthesis, and gas chromatography on a chiral stationary phase.
- Bergmann, Jan,Loefstedt, Christer,Ivanov, Vladimir D.,Francke, Wittko
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p. 3175 - 3179
(2007/10/03)
-
- First asymmetric synthesis of 6-methyl-3-nonanone, the female-produced sex pheromone of the caddisfly Hesperophylax occidentalis
-
The asymmetric synthesis of the female-produced sex pheromone of the caddisfly Hesperophylax occidentalis, (S)-and (R)-6-methyl-3-nonanone, starting from the simple starting materials propanal, propyl iodide and 2-butanone, in good overall yields is described. The stereogenic centre at the C-6 position of the pheromone was generated via α-alkylation employing the SAMP/RAMP hydrazone method with high asymmetric induction (ee = 94 and 92%).
- Enders,Schuesseler
-
p. 973 - 975
(2007/10/03)
-
- Synthetic studies toward amphidinolide A: Synthesis of fully functionalized subunits
-
A retrosynthetic breakdown of amphidinolide A affords four fragments A- D and illustrates the main synthetic challenges of this molecule. A concise stereoselective synthesis of the four appropriately functionalized subtargets is described.
- Terrell, Lamont R.,Ward III, Joseph S.,Maleczka Jr., Robert E.
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p. 3097 - 3100
(2007/10/03)
-
- The total synthesis of (+)-pectinatone: An iterative alkylation approach based on the SAMP-hydrazone method
-
The marine natural product (+)-pectinatone containing 'skip' 1,3- dimethyl stereocentres was synthesised via the iterative alkylation of propanal SAMP-hydrazone with β-branched iodides. Factors affecting the selectivity of the alkylation reaction and the in situ formation of volatile β-branched iodides are described.
- Birkbeck, Anthony A.,Enders, Dieter
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p. 7823 - 7826
(2007/10/03)
-
- Synthesis of (+)-siphonarienone: Asymmetric alkylation using a chiral benzopyrano-isoxazolidine auxiliary
-
Asymmetric alkylation of the potassium enolates derived from N-propionyl benzopyrano[4,3-c]-isoxazolidine derivatives with chiral alkyl triflates proceeded smoothly with high diastereoselectivity. The stereochemistry of the newly formed stereogenic center was fully controlled by the facial selectivity of the enolate according to the rule of double asymmetric synthesis. The application of this methodology led to the first synthesis of (+)-siphonarienone, a marine polypropionate natural product.
- Abiko, Atsushi,Masamune, Satoru
-
p. 1081 - 1084
(2007/10/03)
-
- Pheromone Synthesis, CLXVII. - Synthesis of All of the Eight Stereoisomers of Methyl 2,6,10-Trimethyltridecanoate, the Male-produced Pheromone of the Stink Bugs, Euschistus heros and E. obscurus
-
All of the eight possible stereoisomers of methyl 2,6,10-trimethyltridecanoate (1), the male-produced attractant pheromone of the South American soybean pest, Euschistus heros, and that of E. obscurus, are synthesized by starting from the enantiomers of citronellol (2) and methyl 3-hydroxy-2-methylpropanoate (9). - Key Words: Euschistus heros / Euschistus obscurus / Pheromones / Stink bugs / Sulfones, alkylation of / Tridecanoate, methyl 2,6,10-trimethyl-
- Mori, Kenji,Murata, Noriaki
-
p. 1153 - 1160
(2007/10/02)
-
- Lipase-catalyzed resolution of racemic 2-alkyl substituted 1-alkanols
-
(R)-2-alkyl-1-alkanoids (R)-1 with high optical purities were obtained by lipase-catalyzed esterification of the racemic substrates (R,S)-1 with vinyl acetate in dichloromethane. The alcohols (R)-1 were oxidized without racemization to the corresponding carboxylic acids (R)-4. The enriched (S)-acetates (S)-3 either were saponified to the alcohols (S)-1 which are substrates for a second lipase-catalyzed transesterification to give (S)-1 in high optical purity or were racemized and applied once again in the kinetic resolution to prepare (R)-1.
- Barth,Effenberger
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p. 823 - 833
(2007/10/02)
-
- Asymmetric Syntheses of Chiral Propane-1,3-diols Starting from Malonic Acid
-
Syntheses of chiral intermediates having one tertiary asymmetric centre were carried out via chiral half-esters of monoalkylmalonic acids.The menthyl half-ester of ethylmalonic acid afforded a single diastereoisomer through crystallisation-induced asymmetric transformation (second-order asymmertic transformation).Furthermore enantioselective preparation of unsymmertical propane-1,3-diol derivatives was achieved by the use of 8-phenylmenthyl half-esters.
- Ihara, Masataka,Takahashi, Masanobu,Taniguchi, Nobuaki,Yasui, Ken,Fukumoto, Keiichiro,Kametani, Tetsuji
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p. 897 - 903
(2007/10/02)
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- Camphorsulfonamide-Shielded, Asymmetric 1,4-Additions and Enolate Alkylations; Synthesis of a Southern Corn Rootworm Pheromone
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Using readily accessible 10-sulfonamido-isoborneols as regenerable, chiral auxiliaries, highly face-selective C-C-bond formations at Cα and Cβ of carboxylates could be conveniently achieved.Thus, conjugated additions of RCu to enoates (1->2) furnished, after saponification, β-substituted carboxylic acids 3 in 94-98 percent e.e.Similarly, propionates 12 yielded after deprotonation, enolate alkylation, and reductive ester cleveage the (R)-alcohols 15 in 78-98 percent e.e.The acid (+)-3e was converted to the pheromone (-)-11.
- Oppolzer, Wolfgang,Dudfield, Philip,Stevenson, Thomas,Godel, Thierry
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p. 212 - 215
(2007/10/02)
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- CHIRALITY TRANSFER IN THE ESTER ENOLATE CLAISEN REARRANGEMENT OF (R)-1-METHYL-(E)-2-BUTENYL HYDROXYACETATE AND ITS APPLICATION TO THE STEREOCONTROLLED PHEROMONE SYNTHESIS
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The ester enolate Claisen rearrangement of (R)-1-methyl-(E)-2- butenyl hydroxaacetate provides complete asymmetric transfer along with 98percent erythroselectivity to give (2R,3S)-2-hydroxy-3-methyl-(E)-4-hexenoic acid.Its synthetic utility is demonstrated by the stereocontrolled synthesis of optically active pheromones.
- Fujisawa, Tamotsu,Tajima, Kazuhisa,Sato, Toshio
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p. 1669 - 1672
(2007/10/02)
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- REDUCTION MICROBIOLOGIQUE D'ALDEHYDES α,β-ETHYLENIQUES PAR BEAUVERIA SULFURESCENS
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α,β-unsaturated aldehydes are reduced by Beauveria sulfurescens giving a mixture of the corresponding ethylenic and saturated alcohols.Optically active saturated alcohols have the (S)-configuration.
- Desrut, M.,Kergomard, A.,Renard, M. F.,Veschambre, H.
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p. 3825 - 3830
(2007/10/02)
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- Stereochemistry of Aliphatic Carbocations, 14. Alkyl Shifts from Secondary to Primary Carbon Atoms
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Alkyl shifts from secondary to primary carbon atoms have been induced by the nitrous acid deamination of suitable amines (4, 22, 39, 51); they include sequential rearrangements (-CH3,CH3 and -CH3,H).Predominant although incomplete inversion at the migration origin has been observed (Me 70percent, Et 62-64percent, nPr 65percent, iPr 64percent, tBu 55percent).Our results require the intervention of open secondary carbocations which may be preceded by less stable bridged intermediates.
- Kirmse, Wolfgang,Guenther, Bernd-Rainer,Knist, Johannes,Kratz, Sigrid,Loosen, Karin,et al.
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p. 2127 - 2139
(2007/10/02)
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