- Synthesis and complete structure determination of a sperm-activating and -attracting factor isolated from the ascidian ascidia sydneiensis
-
For the complete structure elucidation of an endogenous sperm-activating and -attracting factor isolated from eggs of the ascidian Ascidia sydneiensis (Assydn-SAAF), its two possible diastereomers with respect to C-25 were synthesized. Starting from ergosterol, the characteristic steroid backbone was constructed by using an intramolecular pinacol coupling reaction and stereoselective reduction of a hydroxy ketone as key steps, and the side chain was introduced by Julia-Kocienski olefination. Comparison of the NMR data of the two diastereomers with those of the natural product led to the elucidation of the absolute configuration as 25S; thus the complete structure was determined and the first synthesis of Assydn-SAAF was achieved.
- Watanabe, Tomohiro,Shibata, Hajime,Ebine, Makoto,Tsuchikawa, Hiroshi,Matsumori, Nobuaki,Murata, Michio,Yoshida, Manabu,Morisawa, Masaaki,Lin, Shu,Yamauchi, Kosei,Sakai, Ken,Oishi, Tohru
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p. 985 - 997
(2018/05/04)
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- Iridium-catalyzed asymmetric hydrogenation of racemic α-substituted lactones to chiral diols
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We report a protocol for the highly efficient iridium-catalyzed asymmetric hydrogenation of racemic α-substituted lactones via dynamic kinetic resolution. Using Ir-SpiroPAP (R)-1d as a catalyst, a wide range of chiral diols were prepared in a high yield (80-95%) with a high enantioselectivity (up to 95% ee) under mild reaction conditions. This protocol was used for enantioselective syntheses of (?)-preclamol and a chiral 2,5-disubstituted tetrahydropyran.
- Yang, Xiao-Hui,Yue, Hai-Tao,Yu, Na,Li, Yi-Pan,Xie, Jian-Hua,Zhou, Qi-Lin
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p. 1811 - 1814
(2017/03/09)
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- Cobalt versus Osmium: Control of Both trans and cis Selectivity in Construction of the EFG Rings of Pectenotoxin 4
-
Catalytic oxidative cyclisation reactions have been employed for the synthesis of the E and F rings of the complex natural product target pectenotoxin 4. The choice of metal catalyst (cobalt- or osmium-based) allowed for the formation of THF rings with either trans or cis stereoselectivity. Fragment union using a modified Julia reaction then enabled the synthesis of an advanced synthetic intermediate containing the EF and G rings of the target.
- Roushanbakhti, Ahria,Liu, Yifan,Winship, Paul C. M.,Tucker, Michael J.,Akhtar, Wasim M.,Walter, Daryl S.,Wrigley, Gail,Donohoe, Timothy J.
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supporting information
p. 14883 - 14887
(2017/10/24)
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- Enantioselective Hydroformylation of 1-Alkenes with Commercial Ph-BPE Ligand
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A rhodium complex, in conjunction with commercially available Ph-BPE ligand, catalyzes the branch-selective asymmetric hydroformylation of 1-alkenes and rapidly generates α-chiral aldehydes. A wide range of terminal olefins including 1-dodecene were examined, and all delivered high enantioselectivity (up to 98:2 er) as well as good branch:linear ratios (up to 15:1). (Chemical Equation Presented).
- Yu, Zhiyong,Eno, Meredith S.,Annis, Alexandra H.,Morken, James P.
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p. 3264 - 3267
(2015/07/15)
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- Facile synthesis of versatile enantioenriched α-substituted hydroxy esters through a Bronsted acid catalyzed kinetic resolution
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An efficient synthesis of enantioenriched α-substituted γ-hydroxy esters via a kinetic resolution event is described. Bulky racemic esters in the presence of a chiral Bronsted acid selectively lactonize to yield a recoverable enantioenriched hydroxy ester and lactone. These esters are highly versatile building blocks that can readily be converted to synthetically useful materials.
- Qabaja, Ghassan,Wilent, Jennifer E.,Benavides, Amanda R.,Bullard, George E.,Petersen, Kimberly S.
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p. 1266 - 1269
(2013/05/09)
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- Using heteroaryl-lithium reagents as hydroxycarbonyl anion equivalents in conjugate addition reactions with (S, S)-(+)-pseudoephedrine as chiral auxiliary; Enantioselective synthesis of 3-substituted pyrrolidines
-
We have developed an efficient protocol for carrying out the stereocontrolled formal conjugate addition of hydroxycarbonyl anion equivalents to α,β-unsaturated carboxylic acid derivatives using (S,S)-(+)-pseudoephedrine as chiral auxiliary, making use of the synthetic equivalence between the heteroaryl moieties and the carboxylate group. This protocol has been applied as key step in the enantioselective synthesis of 3-substituted pyrrolidines in which, after removing the chiral auxiliary, the heteroaryl moiety is converted into a carboxylate group followed by reduction and double nucleophilic displacement. Alternatively, the access to the same type of heterocyclic scaffold but with opposite absolute configuration has also been accomplished by making use of the regio- and diastereoselective conjugate addition of organolithium reagents to α,β,γ,δ-unsaturated amides derived from the same chiral auxiliary followed by chiral auxiliary removal, ozonolysis, and reductive amination/intramolecular nucleophilic displacement sequence.
- Alonso, Beatriz,Ocejo, Marta,Carrillo, Luisa,Vicario, Jose L.,Reyes, Efraim,Uria, Uxue
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p. 614 - 627
(2013/03/13)
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- Chiral methyl trans-2,2-dichloro-3-methylcyclopropanecarboxylate upon exposure to thiophenolate nucleophile
-
Substitution of the β-halogen atoms in methyl (1R,3S)-2,2-dichloro-3- ethylycyclopropanecarboxylate with sodium thiophenolate leads to the di(phenylthio) ester (1RS,3S)-4 as a mixture of diastereomers. The cis-trans isomerisation of methyl (1RS,3S)-3-methyl-2,2-bis(phenylthio)- cyclopropanecarboxylate 4, basic hydrolysis and subsequent crystallization gave the corresponding acid (1R,3S)-5 in high diastereomeric and enantiomeric purity. On the other hand, ring opening of the ester (1RS,3S)-4 under acidic conditions leads to methyl 3-methyl-4,4-di(phenylthio)prop-3-enoate (8) or the chiral S-phenyl thioester methyl (3S)-3-methyl-4-oxo-4-(phenylthio)butanoate (7).ARKAT-USA, Inc.
- Kovalenko, Vitaly N.
-
-
- Direct regiospecific and highly enantioselective intermolecular α-allylic alkylation of aldehydes by a combination of transition-metal and chiral amine catalysts
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The first direct intermolecular regiospecific and highly enantioselective α-allylic alkylation of linear aldehydes by a combination of achiral bench-stable Pd0 complexes and simple chiral amines as co-catalysts is disclosed. The co-catalytic asymmetric chemoselective and regiospecific α-allylic alkylation reaction is linked in tandem with in situ reduction to give the corresponding 2-alkyl alcohols with high enantiomeric ratios (up to 98:2 e.r.; e.r.=enantiomeric ratio). It is also an expeditious entry to valuable 2-alkyl substituted hemiacetals, 2-alkyl-butane-1,4-diols, and amines. The concise co-catalytic asymmetric total syntheses of biologically active natural products (e.g., Arundic acid) are disclosed. Go organic! Direct intermolecular regiospecific and highly enantioselective α-allylic alkylation of linear aldehydes by a combination of achiral bench-stable Pd0 complexes and simple chiral amines as co-catalysts is disclosed (see scheme). Copyright
- Afewerki, Samson,Ibrahem, Ismail,Rydfjord, Jonas,Breistein, Palle,Cordova, Armando
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p. 2972 - 2977
(2012/04/11)
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- INDANE ESTROGEN RECEPTOR MODULATORS AND USES THEREOF
-
Described herein are compounds that are estrogen receptor modulators. Also described are pharmaceutical compositions and medicaments that include the compounds described herein, as well as methods of using such estrogen receptor modulators, alone and in combination with other compounds, for treating diseases or conditions that are mediated or dependent upon estrogen receptors.
- -
-
Page/Page column 94-95
(2012/01/06)
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- ESTROGEN RECEPTOR MODULATORS AND USES THEREOF
-
Described herein are compounds that are estrogen receptor modulators. Also described are pharmaceutical compositions and medicaments that include the compounds described herein, as well as methods of using such estrogen receptor modulators, alone and in combination with other compounds, for treating diseases or conditions that are mediated or dependent upon estrogen receptors.
- -
-
Page/Page column 105; 106
(2012/01/05)
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- The resolution of trans-2,2-dichloro-3-methylcyclopropanecarboxylic acid via crystallization of its salts with (+)- and (-)-α-phenylethylamine, and the transformation of the resulting enantiomers into (R)- and (S)-dimethyl 2-methylsuccinates
-
The resolution of trans-2,2-dichloro-3-methylcyclopropanecarboxylic acid trans-1 was achieved by crystallization of its salts with (+)- and (-)-α-phenylethylamine. The chiral acids were converted into methyl esters 9, which upon reaction with sodium methoxide in methanol underwent a three-carbon ring cleavage, leading to the corresponding mono-orthoester derivatives 10. Acidic hydrolysis then gave the known (R)- and (S)-dimethyl 2-methylsuccinates 12.
- Kovalenko, Vitaly N.,Kulinkovich, Oleg G.
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experimental part
p. 26 - 30
(2011/04/18)
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- Chemo-biological preparation of the chiral building block (R)-4-acetoxy-2-methyl-1-butanol using Pseudomonas putida
-
In order to develop new methyl substituted chiral building blocks which are useful for the synthesis of methyl branched natural products, the enantioselective bioreduction of an exo-methylene to a methyl group was investigated. 4-Acetoxy-2-methylene-1-butanol 3 was prepared from itaconic acid over four steps and converted to the chiral alcohol (R)-4-acetoxy-2-methyl-1- butanol 4, by growing cells of Pseudomonas putida. The bioconversion achieved a high enantioselectivity (92% ee) and a high chemical yield (65%) within a relatively short reaction time (18-20 h). Copyright
- Kim, Youngju,Watanabe, Hidenori,Kim, Bieong-Kil,Seu, Young-Bae
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p. 1658 - 1661
(2012/01/13)
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- Formal synthesis of the anti-angiogenic polyketide (-)-borrelidin under asymmetric catalytic control
-
Borrelidin (1) is a polyketide that possesses extremely potent antiangiogenesis activity. This paper describes its formal total synthesis by the most efficient route to date. This modular approach takes optimal benefit of asymmetric catalysis and permits the synthesis of analogues; in addition, the high yields and selectivities obtained eliminate the need for separation of stereoisomers. The upper half of borrelidin has been accessed by iterative copper-catalysed asymmetric conjugate addition of methylmagnesium bromide, whereas synthesis of the lower half of the molecule was achieved by relying on asymmetric hydrogenation and cross-methathesis as key steps.
- Madduri, Ashoka V. R.,Minnaard, Adriaan J.
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supporting information; experimental part
p. 11726 - 11731
(2010/11/18)
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- A concise asymmetric synthesis of (2S,3S,7S)-3,7-dimethylpentadecan-2-yl acetate and propionate, the sex pheromones of pine sawflies
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(2S,3S,7S)-3,7-Dimethylpentadecan-2-yl acetate (2) and its propionate analogue (3) are the main sex pheromones of all Neodiprion species and Diprion similes, respectively. Starting from (S)-malic acid and employing a highly chemo-, regio-, and stereoselective tandem ester reduction-epoxide formation-reductive epoxide-opening reaction protocol, an efficient total synthesis of (2S,3S,7S)-2 and -3 is reported herein.
- Huang, Pei-Qiang,Lan, Hong-Qiao,Zheng, Xiao,Ruan, Yuan-Ping
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p. 3964 - 3967
(2007/10/03)
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- Asymmetric synthesis of 2-substituted butane-1,4-diols by hydrogenation of homochiral fumaramide derivatives
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Diastereoselective hydrogenation of homochiral fumaramides 1 derived from (2R)-Oppolzer's sultam was observed by analysis of the 1H NMR spectra of the succinamide mixtures with de's of 77-88%. Reduction of these succinamides using LiAlH4 gave the corresponding (2S)-butane-1,4- diols and established that addition of hydrogen takes place selectively on the re-face of fumaramides 1. The stereoselectivity was confirmed by estimating the ee's from the 19F NMR spectra of the Mosher's diesters of the diols. This methodology was applied to the synthesis of selected pyrrolidine natural products in homochiral form.
- Jawaid, Samaila,Farrugia, Louis J.,Robins, David J.
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p. 3979 - 3988
(2007/10/03)
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- Oxabicyclo[3.2.1]oct-6-enes as templates for the stereoselective synthesis of polypropionates: Total synthesis of callystatin a and C19-epi-callystatin A
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The total synthesis of the polyketide natural product callystatin A and its novel analog C19-epi-callystatin A is described. Our strategy features the use of an enantiomerically pure oxabicyclo[3.2.1]oct-6-ene as a template for the stereocontrolled preparation of the C15-C21 polypropionate region.
- Lautens, Mark,Stammers, Timothy A.
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p. 1993 - 2012
(2007/10/03)
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- A new asymmetric synthesis of (R)-3-methylpyrrolidine alkaloids starting from (S)-malic acid
-
Diastereoselective methylation of dimethyl (S)-malate (8) followed by two three-step reductive dehydroxylation procedures afforded dimethyl (R)-2-methylsuccinate (16) in 80.2% and 84.7% ee respectively, the later was further transformed into the natural enantiomers of ant venom alkaloids (R)-leptothoracine (1) and (R)-3-methyl-N-(2-phenylethyl)pyrrolidine (2) and (3R, 2'S)-3-methyl-N-(2-methylbutyl)pyrrolidine (3).
- Zheng, Xiao,Huang, Pei Qiang,Ruan, Yuan Ping,Lee, Albert W. M.,Chan, Wing Hong
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p. 1505 - 1518
(2007/10/03)
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- Optical rotation computation, total synthesis, and stereochemistry assignment of the marine natural product Pitiamide A
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We report the joint application of ab initio computations and total synthesis to assign the absolute configuration of a new natural product. The expected specific rotations of the (7S,10R)- and (7R,10R)-isomers of pitiamide A in a CHCl3 solvent continuum model were determined as +8 and -39, respectively, by CADPAC calculations of the electric-dipole-magnetic-dipole polarizability tensor. Total syntheses of these two stereoisomers of the marine metabolite were achieved by a convergent strategy that utilized Evans' oxazolidinone alkylation, a novel water-accelerated modification of Negishi's zirconocene-catalyzed asymmetric carbometalation as well as an unusual segment condensation via Mitsunobu alkylation of a nosyl-activated amide. The experimental optical rotation measurements confirmed the results of the computational optical rotation predictions. On the basis of NMR comparisons, the configuration of pitiamide A was assigned as (7R,10R). These studies highlight the considerable structural significance of [α]D data, but, because the optical rotation of the natural product was different from either synthetic diastereomer, our work serves also as an illustration of potential problems with obtaining accurate experimental [α]D data for natural samples.
- Ribe, Seth,Kondru, Rama K.,Beratan, David N.,Wipf, Peter
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p. 4608 - 4617
(2007/10/03)
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- Asymmetric synthesis of 1,3- and 1,3,4-substituted pyrrolidines
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Diastereoselective alkylation of N-acylnorbornene sultams 2 afforded a variety of enantiomerically pure products 3a-3e. Reduction with LiAlH4 (LAH) followed by ditosylation furnished chiral 1,4-ditosylates 5a-5e which underwent a cyclization reaction with primary amines to afford chiral 1,3- and 1,3,4-substituted pyrrolidines. (C) 2000 Elsevier Science Ltd.
- Lin, Jing,Chan, Wing Hong,Lee, Albert W. M.,Wong, Wai Yeung,Huang, Pei Qiang
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p. 2949 - 2951
(2007/10/03)
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- Total synthesis of cytochalasin D: Total synthesis and full structural assignment of cytochalasin O
-
A total synthesis of cytochalasin D 3 is reported in which the key step is an intramolecular Diels-Alder reaction used to close the 11-membered ring simultaneously introducing the required stereochemistry at four of the stereogenic centres, C(4), C(5), C(8) and C(9). The precursor 21 for the Diels-Alder reaction was prepared from the aldehyde 13 by condensation with the dienyl phosphonate 14 to give the triene 15 which, after conversion into the acyl imidazole 17, was used to acylate the pyrrolidinone 18. The unstable pyrrolinone 21 was then generated from the pyrrolidinone by phenylselenation-oxidative elimination and was cyclised by heating in toluene under high dilution conditions to give the macrocyclic triene 22 (25-30%). Selective functionalisation of the double-bonds in this triene was investigated with epoxidation being selective for the 17,18-double-bond and hydroxylation using osmium tetroxide taking place selectively at the 6,7-double-bond. For completion of the synthesis of cytochalasin D 3, the 6,7-diol 26 was converted into the exocyclic alkene 30 by protection and dehydration. Further hydroxylation using osmium tetroxide gave the diol 31 which was taken through to the enone 36 by protection followed by phenylselenation, N-debenzoylation and oxidative elimination. Reduction under Luche's conditions gave the alcohol 37 which was converted into the acetate 41 by acetylation followed by protecting group exchange. Selective deprotection of the vicinal diol and mild oxidation then gave the ketone 43. Final deprotection gave cytochalasin D 3 so completing the first total synthesis of this natural product. During the course of this work, the Diels-Alder adduct 22 was oxidised using an excess of osmium tetroxide to give the tetraol 28. After protection as its bis-acetonide 46, this was converted into the allylic acetate 51 using the chemistry developed during the synthesis of cytochalasin D 3. Selective hydrolysis of the 17,18-acetonide and oxidation under Swern conditions gave the hydroxyketone 53 which on deprotection gave cytochalasin O 54 so confirming the structure of this natural product. The Royal Society of Chemistry 1999.
- Merifield, Eric,Thomas, Eric J.
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p. 3269 - 3283
(2007/10/03)
-
- Simple synthesis of both enantiomers of 3-methyl-N-(3-methylbutyl)pyrrolidine
-
(S)-3-Methyl-N-(3-methylbutyl)pyrrolidine (1) and its anti-pode (R)-1 have been prepared by reduction of (S)-4,5-dihydro-3-methyl-2(3H)furanone (7) and dimethyl (R)-2-methylsuccinate (11), bromination thereof, and ring closure of the intermediates (S)-9 and R)-9, respectively, with 3-methylbutylamine (10). An alternative synthesis of (A)-1 by mesylation of (R)-8 is also described. Both enantiomers of 1 were obtained in excellent enantiomeric excesses (ee = 96%). VCH Verlagsgesellschaft mbH, 1997.
- Veith, Hans Juergen,Collas, Markus,Zimmer, Reinhold
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p. 391 - 394
(2007/10/03)
-
- Studies on the enantioselectivity of the transesterification of 2-methyl-1,4-butanediol and its derivatives catalyzed by Pseudomonas fluorescens lipase in organic solvents
-
The irreversible transesterification of 2-methy-1,4-butanediol 1a and its benzyl ethers 2a and 3a catalyzed by Pseudomonas fluorescens lipase in chloroform was studied, the highest ee (> 98%) having been obtained for the 4-benzyl ether 2a.
- Grisenti,Ferraboschi,Casati,Santaniello
-
p. 997 - 1006
(2007/10/02)
-
- Asymmetric 1,4-additions to γ-menthyloxybutenolides. Part IV. Two enantioselective syntheses of 2-methyl-1,4-butanediol
-
Based on the asymmetric Michael addition to 5(R)- and 5(S)-menthyloxy-2[5H]-furanone two new syntheses of enantiomerically pure R- and S-2-methyl-1,4-butanediol are described.
- Jansen,Feringa
-
p. 1367 - 1376
(2007/10/02)
-
- Asymmetric catalysis. Production of chiral diols by enantioselective catalytic intramolecular hydrosilation of olefins
-
Rhodium(I) chiral diphosphine complexes efficiently and rapidly catalyze the intramolecular hydrosilation of silyl ethers derived from allylic alcohols. The efficiency and rates of intramolecular hydrosilations were determined for a variety of silyl and olefin substituents. The catalysts were found to tolerate a wide variety of silyl substituents, although terminal alkyl olefin substituents were found to retard catalysis. Terminal aryl olefin substituents were found to be hydrosilated efficiently and at reasonable rates. One of the chiral catalysts is highly enantioselective for terminal aryl olefin substituents. Almost quantitative ee's are obtained. Moreover, the ee's are only slightly sensitive to aryl and olefin substituents, suggesting that this enantioselective catalysis can provide a wide range of chiral species. Oxidative cleavage of the hydrosilation products gives chiral diols.
- Bergens, Steven H.,Noheda, Pedro,Whelan, John,Bosnich
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p. 2121 - 2128
(2007/10/02)
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- Highly S(N)2'-, (E)-, and antiselective alkylation of allylic phosphates. Facile synthesis of coenzyme Q10
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Treatment of secondary allylic chlorides or allylic phosphates in tetrahydrofuran with prenyl Grignard reagent in the presence of CuCN · 2 LiCl gave geraniol or farnesol derivatives with high S(N)2' selectivity. Phosphate leaving groups were highly transstereoselective for the formation of (E,E)-farnesol derivatives. Furthermore, complete anti-S(N)2' selectivity was observed in the alkylation of optically active allylic phosphates. The present method appears to be an excellent carbon-carbon coupling reaction with high regio-, (E)-, and enantioselectivity. Coenzyme Q10 (ubiquinone 10) was efficiently synthesized using this methodology.
- Yanagisawa,Nomura,Noritake,Yamamoto
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p. 1130 - 1136
(2007/10/02)
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- Synthesis of Optically Active Bifunctional Isoprenoid Building Blocks by Rhodium(I)-Catalyzed Asymmetric Allylamine to Enamine Isomerization
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The application of the known asymmetric allylamine to enamine isomerization methodology to bifunctional C5-isoprenoid allylic amines of types IId and IIe (Scheme 1) is described.It is shown that a number of such substrates can be isomerized with enantioselectivities of >90percent ee using cationic RhI complexes containing (6,6'-dimethylbiphenyl-2,2'-diyl)bis(diphenylphosphine) (BIPHEMP; 9) as asymmetry-inducing ligand (Scheme 2, Tables 1 and 2).Synthetically most useful is the isomerization of the benzyloxy derivative 10a into the (E)-enamine 11a.This isomerization proceeds with very high enantioselectivity (98-99percent ee) and affords, after enamine hydrolysis, the optically active 4-(benzyloxy)-3-methylbutanals ((R)- or (S)-12) in chemical yields of ca. 90percent.In conjunction, a short synthetic route to the starting material 10a has been developed which has a Pd-catalyzed amination of isoprene epoxide (30) as the key step.Thus, convenient and practical access to the optically active aldehydes (R)- and (S)-12 is now at hand.These aldehydes are useful optically active bifunctional building blocks for isoprenoid homologation.
- Schmid, Rudolf,Hansen, Hans-Juergen
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p. 1258 - 1275
(2007/10/02)
-
- ASYMMETRIC 1,4-ADDITIONS TO γ-MENTHYLOXYBUTENOLIDES. ENANTIOSPECIFIC SYNTHESIS OF CHIRAL 1,4-BUTANEDIOLS.
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Optically active methyl-substituted butanediols and γ-lactones were prepared from γ-menthyloxy-2--furanone.
- Jansen, Johan F.G.A.,Feringa, Ben L.
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p. 5481 - 5484
(2007/10/02)
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- Norephedrine-Derived 2-Alkenyloxazolidines: Stereochemistry of Cyclization and Allylic Stereocenter Directed Asymmetric Conjugate Addition
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A study on the stereochemistry of the acid-catalyzed cyclization between N-protected norephedrine and α,β-unsaturated dimethyl acetals to give the title compounds is reported.Such heterocycles, on the basis of their different formation and reactivity beha
- Bernardi, Anna,Cardani, Silvia,Pilati, Tullio,Poli, Giovanni,Scolastico, Carlo,Villa, Roberto
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p. 1600 - 1607
(2007/10/02)
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- ENANTIOSELECTIVE ALKYLATIONS OF γ-OXO ESTERS
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Chiral oxazolidine derivatives of the title compounds are transformed into ester enolates which are diastereoselectively alkylated.Subsequent hydrolysis leads to optically active α-alkyl γ-oxo esters.
- Agami, C.,Meynier, F.,Rizk, T.
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p. 241 - 250
(2007/10/02)
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- Allylic Stereocenter Directed Asymmetric Conjugate Addition. Enantioselective Synthesis of 3-Alkylsuccinaldehydic Acid Methyl Esters
-
Cuprate reagents add to ester 2 with excellent ?-face selectivity (>=95:5) and furnish the title compounds in high enantiomeric excess after removal of the chiral auxiliary.
- Bernardi, Anna,Cardani, Silvia,Poli, Giovanni,Scolastico, Carlo
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p. 5041 - 5043
(2007/10/02)
-