- Investigation of Electrostatic Interactions towards Controlling Silylation-Based Kinetic Resolutions
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Electrostatic interactions between a silylated isothiourea intermediate and an ester π system were explored by determining how variations in sterics and electronics affect the selectivity of a silylation-based kinetic resolution. Sterics on the π systems affect the selectivity factors of alkyl 2-hydroxycyclohexanecarboxylates, resulting in a strong correlation of selectivity factors to Charton values. Induction effects of electron-withdrawing substituents on phenyl esters significantly enhance selectivity supporting an edge to face π–π interaction. The linear free energy relationships that were uncovered will aid in future incorporation of intermolecular electrostatic interactions towards controlling asymmetric reactions.
- Zhang, Tian,Redden, Brandon K.,Wiskur, Sheryl L.
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supporting information
p. 4827 - 4831
(2019/08/12)
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- Chemoenzymatic approaches to the synthesis of the (1S,2R)-isomer of benzyl 2-hydroxycyclohexanecarboxylate
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We examined ten strains of cultured whole-cell yeasts for the asymmetric reduction of commercially available ethyl 2-oxocyclohexanecarboxylate, and found that the (1S,2S)-stereoisomer of ethyl 2-hydroxycyclohexanecarboxylate was the major stereoisomer produced by Williopsis californica JCM 3600. The ethyl group of the ester was then substituted with a benzyl group with low volatility and increased hydrophobicity to facilitate the isolation of the expected product. Incubation with W. californica furnished benzyl (1S,2S)-2-hydroxycyclohexanecarboxylate (>99.9% ee) in 51.0% yield together with its (1R,2S)-isomer (>99.9% ee) in 35.4% yield. Upon treatment of the same substrate bearing the benzyl ester with a screening kit of purified overexpressed carbonyl reductases (Daicel Chiralscreen OH), two enzymes (E031, E078) furnished the (1R,2S)-isomer as the major product. With another enzyme (E007), the (1S,2R)-isomer was obtained, but its ee was very low (25.6%). The highly enantiomerically enriched (1S,2S)-isomer obtained by W. californica was transformed to the (1S,2R)-isomer (>99.9% ee), whose availability until now has been low, in 43.3% yield over two steps involving tosylation and subsequent inversive attack with tetrabutylammonium nitrite.
- Tsunekawa, Ryuji,Hanaya, Kengo,Higashibayashi, Shuhei,Shoji, Mitsuru,Sugai, Takeshi
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- BIARYL PYRAZOLES AS NRF2 REGULATORS
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The present invention relates to biaryl pyrazole compounds, methods of making them, pharmaceutical compositions containing them and their use as NRF2 regulators.
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Page/Page column 455
(2017/08/01)
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- New Route to Stabilize Ruthenium Nanoparticles with Non-Isolable Chiral N-Heterocyclic Carbenes
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Ru nanoparticles (RuNPs) stabilized by non-isolable chiral N-heterocyclic carbenes (NHCs), namely SIDPhNp ((4S,5S)-1,3-di(naphthalen-1-yl)-4,5-diphenylimidazolidine) and SIPhOH ((S)-3-((1S,2R)-2-hydroxy-1,2-diphenylethyl)-1-((R)-2-hydroxy-1,2-diphenylethyl)-4,5-dihydro-3H-imidazoline), have been synthesized through a new procedure that does not require isolation of the free carbenes. The obtained RuNPs have been characterized by state-of-the-art techniques and their surface chemistry has been investigated by FTIR and solid-state MAS NMR upon the coordination of CO, which indicated the presence of free and reactive Ru sites. Their catalytic activity has been tested in various hydrogenation reactions involving competition between different sites, whereby interesting differences in selectivity were observed, but no enantioselectivity.
- Martnez-Prieto, Luis Miguel,Ferry, Anglique,Lara, Patricia,Richter, Christian,Philippot, Karine,Glorius, Frank,Chaudret, Bruno
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p. 17495 - 17502
(2016/01/25)
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- Synthesis and characterization of the enantiomerically pure cis- and trans-2,4-dioxa-3-fluoro-3-phosphadecalins as inhibitors of acetylcholinesterase
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The title compounds, the P(3)-axially- and P(3)-equatorially-substituted cis- and trans-configured 3-fluoro-2,4-dioxa-3-phosphadecalin 3-oxides (= 3-fluoro-2,4-dioxa-3-phosphabicyclo[4.4.0]decane 3-oxides) have been prepared (ee > 99%) and fully character
- Waechter, Michael,Rueedi, Peter
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experimental part
p. 283 - 294
(2010/04/23)
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- Carbonylative ring opening of terminal epoxides at atmospheric pressure
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(Chemical Equation Presented) The carbonylative opening of terminal epoxides under mild conditions has been developed using Co2-(CO) 8 as the catalyst. Under 1 atm of carbon monoxide and at room temperature in methanol, propylene oxide is converted to methyl 3-hydroxybutanoate in up to 89% yield. This transformation is general for many terminal epoxides bearing alkyl, alkenyl, aryl, alkoxy, chloromethyl, phthalimido, and acetal functional groups. The opening takes place without epimerization at the secondary stereocenter.
- Denmark, Scott E.,Ahmad, Moballigh
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p. 9630 - 9634
(2008/03/17)
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- Reductions of cyclic β-keto esters by individual Saccharomyces cerevisiae dehydrogenases and a chemo-enzymatic route to (1R,2S)-2-methyl-1-cyclohexanol
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Twenty purified dehydrogenases cloned from bakers' yeast (Saccharomyces cerevisiae) and expressed as fusion proteins with glutathione (S)-transferase were tested for their ability to reduce three homologous cyclic β-keto esters. The majority of dehydrogenases reduced ethyl 2-oxo-cyclopentanecarboxylate, yielding a pair of diastereomeric alcohols with consistent (1R)-stereochemistry. Ethyl 2-oxo-cyclohexanecarboxylate reductions afforded only cis-alcohol enantiomers. Ethyl 2-oxo-cycloheptanecarboxylate was accepted by two enzymes in the collection, and both yielded mainly the cis-(1R,2S)-alcohol. Escherichia coli cells overexpressing the YDL124w gene were used in a dynamic kinetic resolution of ethyl 2-oxo-cyclohexanecarboxylate to produce the key intermediate in a chemo-enzymatic synthesis of (1R,2S)-2-methyl-1-cyclohexanol, an important chiral building block.
- Padhi, Santosh Kumar,Kaluzna, Iwona A.,Buisson, Didier,Azerad, Robert,Stewart, Jon D.
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p. 2133 - 2138
(2008/02/11)
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- Rhodium-catalyzed reformatsky-type reaction
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(equation presented) A novel Reformatsky-type reaction was developed using RhCl(PPh3)3 and diethylzinc. Inter- and intramolecular Reformatsky-type reactions were achieved efficiently under mild reaction conditions to give β-hydroxy esters.
- Kanai, Kazuo,Wakabayashi, Hitoshi,Honda, Toshio
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p. 2549 - 2551
(2007/10/03)
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- Stereoselective synthesis of novel anti-MRSA tricyclic carbapenems (trinems)
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(4S)-Hydroxymethyltrinem 3 was prepared via stereoselective aldol-type reaction with optically pure (R)-2-t-butyldimethylsilyloxymethylcyclohexanone ((R)-16). (4S)-Hydroxymethyltrinem 3 was converted into various kinds of trinem derivatives with anti-MRSA activity by using the Mitsunobu reaction. (C) 2000 Elsevier Science Ltd.
- Kanno, Osamu,Kawamoto, Isao
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p. 5639 - 5648
(2007/10/03)
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- BENZAMIDINE DERIVATIVES SUBSTITUTED BY CYCLIC AMINO ACID AND CYCLIC HYDROXY ACID DERIVATIVES AND THEIR USE AS ANTI-COAGULANTS
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This invention is directed to benzamidine derivatives substituted by cyclic amino acid and cyclic hydroxy acid derivatives which are useful as anti-coagulants. This invention is also directed to pharmaceutical compositions containing the compounds of the invention, and methods of using the compounds to treat disease-states characterized by thrombotic activity.
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- Highly stereocontrolled synthesis of enantiomeric 4-methoxy trinems via resolution of scalemic enol phosphates
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Stereocontrolled syntheses of 4-methoxy trinem 2 and its enantiomer 3 were achieved using the ester enolate N-trimethylsilylimine approach. The key step was the resolution of racemic enolphosphates derived from ephedrine.
- Panunzio, Mauro,Camerini, Roberto,Pachera, Roberta,Donati, Daniele,Marchioro, Carla,Perboni, Alcide
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p. 2929 - 2938
(2007/10/03)
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- Highly stereocontrolled synthesis of a novel tribactam by reaction of an ester enolate with a N-trimethylsilylimine
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The azetidinone 14, a key intermediate in the synthesis of novel tribactam antibiotics (e.g. 2) was obtained via condensation of an ester enolate with a N-trimethylsilylimine.
- Camerini, Roberto,Panunzio, Mauro,Bonanomi, Giorgio,Donati, Daniele,Perboni, Alcide
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p. 2467 - 2470
(2007/10/03)
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- Stereo- and chemoselective transfer hydrogenation of carbonyl groups with RuCl2(PPh3)3 and BINAP-Ru as catalysts and et3NH+H2PO2-·1,5H 2O as a hydrogen donor
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Using Et3NH+H2PO2-.1.5 H2O as a hydrogen donor, the RuCl2(Ph3P)3, RuCl2(PPh3)3 / C and BINAP-Ru proved highly active catalysts for transfer hydrogenation of ketones under milder conditions than other hydrogen donors. 2-Methyl-, 2-chloro-, 2-(ethoxycarbonyl)cyclohexanones and -cyclopentanones were reduced to the less stable axial alcohols in excellent diastereoisomeric excess (de: 90-100%), and the carbonyl group of α,β-unsaturated ketones was selectively reduced, in contrast with other hydrogen donors the C=C bond was reduced. Copyright
- Khai, Bui The,Arcelli, Antonio
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p. 6599 - 6602
(2007/10/03)
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- Heterocyclic compounds
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A method of combating undesired plant growth in wheat, comprising treating said undesired plant growth with an effective amount of a compound of the formula I STR1 in which n is an integer from 1 to 6; m is an integer from 0 to 2n+2; X represents an oxyge
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- Stereoelectronic Influence on the NaBH4 Reduction Stereoselectivity of Alicyclic β-ketoesters
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The stereochemistry of β-hydroxyesters produced in the NaBH4 reduction of alicyclic β-ketoesters has been determined.An enhanced rate of reduction has been observed for those isomers in which the carboxylate is antiperiplanar to the hydride ion in the tra
- Beeson, Craig,Pham, Nguyen,Dix, Thomas A.
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p. 2925 - 2928
(2007/10/02)
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- Studies on the Chemo- and Enantio-selectivity of the Enzymatic Monoacylations of Amino Alcohols
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The formation of ω-aminoalkyl esters through the lipase PS (Pseudomonas cepacia)-catalysed transesterification between carboxylic acid esters 1-6 and ω-amino-1-alkanols in tert-amyl alcohol has been studied.For n = 5 or 6 the reaction practically leads to the formation of the ester product.The ester/amide ratios decrease with decreasing n so that for n = 3 only the amide product is obtained.A moderate kinetic resolution (ca. 50percent e.e. at 50percent conversion) was found in the acylations with two of the racemic starting esters (3 and 4).
- Kanerva, Liisa T.,Kosonen, Markus,Vaenttinen, Eero,Huuhtanen, Tuomas T.,Dahlqvist, Martti
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p. 1101 - 1105
(2007/10/02)
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- Heterocyclic compounds
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Compounds of formula I wherein nis 1 to 6; mis 0 to 2n+2; X is oxygen, sulphur, sulphinyl or sulphonyl; R1, R2 and R3 are each, independently, hydrogen, halogen, formyl, cyano, carboxy, azido or optionally substituted alkyl, alkenyl, alkynyl, alkoxy, alke
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- Synthesis of β-Hydroxy Esters by Lithium/Ammonia Reduction of α,β-Epoxy Esters
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Aliphatic β-hydroxy esters (alkyl 3-hydroxyalkanoates) are conveniently prepared in high yield by regioselective lithium /ammonia reduction of α,β-epoxy esters (alkyl 2,3-epoxyalkanoates).
- Baan, J. L. van der,Barnick, J. W. F. K.,Bickelhaupt, F.
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p. 897 - 899
(2007/10/02)
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- 65. Homogeneous and Heterogeneous Asymmetric Reactions. Part 5. Diastereoselective and Enantioselective Hydrogenation of Cyclic β-Keto Esters on Modified Raney-Nickel Catalysts
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The hydrogenations of methyl 2-oxocyclopentanecarboxylate (1), ethyl 2-oxocyclohexanecarboxylate (3), and 2-methylcyclohexanone (5) on unmodified Raney-Ni catalyst lead predominantly to the formation of the cis-hydroxy diastereoisomers of 2, 4, and 6, respectively (Scheme 2).In the asymmetric hydrogenations on catalysts modified with chiral tartaric acid (R,R)-C4H6O6/Raney-Ni and (R,R)-C4H6O6/NaBr/Raney-Ni), the predominance of the cis-isomer increases significantly.The hydrogenations of β-keto esters 1 and 3 proceed with an enantioselectivity of 10-15percent on the modified catalysts, while the similar hydrogenation of 5 yields optically inactive 6.The (1S,2R)-enantiomers of the cis-isomers of 2 and 4 are formed in larger quantity, whereas the (1R,2R)-enantiomers of the corresponding trans-isomers predominate (Scheme 1).The enantioselective formation of trans-2 and trans-4 can be interpreted mainly in terms of the asymmetric hydrogenation of cyclic β-keto esters through the keto form, while that of the corresponding cis-hydroxy esters proceeds through the enol form.
- Wittmann, Gyula,Goendoes, Gyoergy,Bartok, Mihaly
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p. 635 - 639
(2007/10/02)
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- Pyrimidine derivatives and herbicide containing the same
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Disclosed are pyrimidine derivatives of the formula (I) and optical isomers thereof and a herbicide containing one or more of them as an active ingredient. STR1 where W is O or S; X is a lower alkyl group or a lower alkoxycarbonyl group; R is H, an option
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- DIASTEREOSELECTIVE AND ENANTIOSELECTIVE MICROBIAL REDUCTION OF CYCLIC alpha-ALKYL beta-KETOESTERS
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The reduction of racemic cyclopenta- and cyclohaxanone 2-carboxyesters by various yeast and mould strains was shown to produce different amounts of isomeric beta-hydroxyesters with predominant (1S) stereochemistry.With several strains, only one optically
- Buisson, Didier,Azerad, Robert
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p. 2631 - 2634
(2007/10/02)
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- 144. Ueber die Stereoselektivitaet der α-Alkylierung von (1R,2S)(+)-cis-2-Hydroxy-cyclohexancarbonsaeureaethylester
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In continuation of our work on the stereoselectivity of the α-alkylation of β-hydroxyesters , we studied this reaction with the title compound (+)-2.The latter was prepared through reduction of 1 with baker's yeast.Alkylation of the dianion of (+)-
- Frater, Gyoergy
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p. 1383 - 1390
(2007/10/02)
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- The synthetic utility of amine borane reagents in the reduction of aldehydes and ketones
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Primary and secondary amine boranes have been shown to be mild, efficient, and stereoselective reducing agents for aldehydes and ketones in protic or non-protic solvents with reactivity patterns different than diborane or sodium borohydride.
- Andrews,Crawford
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p. 693 - 696
(2007/10/02)
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