- Mechanochemical enzymatic resolution of N-benzylated-β3-amino esters
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The use of mechanochemistry to carry out enantioselective reactions has been explored in the last ten years with excellent results. Several chiral organocatalysts and even enzymes have proved to be resistant to milling conditions, which allows for rather efficient enantioselective transformations under ball-milling conditions. The present article reports the first example of a liquid-assisted grinding (LAG) mechanochemical enzymatic resolution of racemic β3-amino esters employing Candida antarctica lipase B (CALB) to afford highly valuable enantioenriched N-benzylated-β3-amino acids in good yields. Furthermore the present protocol is readily scalable.
- Pérez-Venegas, Mario,Reyes-Rangel, Gloria,Neri, Adrián,Escalante, Jaime,Juaristi, Eusebio
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supporting information
p. 1728 - 1734
(2017/09/27)
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- Characterization of FabG and FabI of the Streptomyces coelicolor dissociated fatty acid synthase
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Streptomyces coelicolor produces fatty acids for both primary metabolism and for biosynthesis of the secondary metabolite undecylprodiginine. The first and last reductive steps during the chain elongation cycle of fatty acid biosynthesis are catalyzed by FabG and FabI. The S. coelicolor genome sequence has one fabI gene (SCO1814) and three likely fabG genes (SCO1815, SCO1345, and SCO1846). We report the expression, purification, and characterization of the corresponding gene products. Kinetic analyses revealed that all three FabGs and FabI are capable of utilizing both straight and branched-chain β-ketoacyl-NAC and enoyl-NAC substrates, respectively. Furthermore, only SCO1345 differentiates between ACPs from both biosynthetic pathways. The data presented provide the first experimental evidence that SCO1815, SCO1346, and SCO1814 have the catalytic capability to process intermediates in both fatty acid and undecylprodiginine biosynthesis.
- Singh, Renu,Reynolds, Kevin A.
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p. 631 - 640
(2015/03/31)
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- Proton pump inhibitors
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A proton pump inhibitor containing a compound represented by the formula (I) wherein X and Y are the same or different and each is a bond or a spacer having 1 to 20 carbon atoms in the main chain, R 1 is an optionally substituted hydrocarbon group or an optionally substituted heterocyclic group, R 2 , R 3 and R 4 are the same or different and each is a hydrogen atom, an optionally substituted hydrocarbon group, an optionally substituted thienyl group, an optionally substituted benzo[b]thienyl group, an optionally substituted furyl group, an optionally substituted pyridyl group, an optionally substituted pyrazolyl group, an optionally substituted pyrimidinyl group, an acyl group, a halogen atom, a cyano group or a nitro group, R 5 and R 6 are the same or different and each is a hydrogen atom or an optionally substituted hydrocarbon group, which has a superior proton pump action and shows an antiulcer activity and the like after conversion to a proton pump inhibitor in the body, or a salt thereof. or a prodrug thereof is provided.
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Paragraph 0261
(2015/11/16)
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- Polystyryl-BEMP as an efficient recyclable catalyst for the nucleophilic addition of nitroalkanes to α,β-unsaturated carbonyl compounds under solvent-free conditions
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2-tert-Butylimino-2-diethylamino-1,3-dimethylperhydro-1,3, 2-diazaphosphorine supported on polystyrene (PS-BEMP) is an efficient catalyst for the addition of nitroalkanes (1-1.5 equiv.) to α,β-unsaturated carbonyl compounds (1.0 equiv.) in the absence of a reaction medium (solvent-free conditions). The corresponding γ-nitro carbonyl compounds have been isolated in excellent yields but the catalyst can be satisfactorily recovered and used for only 3 times due to the magnetic stirring which caused crunching of the catalyst beads thus hampering its complete recovery. To optimize the catalyst's reuse and improve the environmental efficacy of solvent-free conditions, the first solvent-free cyclic continuous-flow reactor has been set up. This reactor has allowed the product to be isolated in an almost quantitative yield by using a very small amount of organic solvent, making the recovery and reuse of the catalyst efficient and reproducible.
- Ballini,Barboni,Castrica,Fringuelli,Lanari,Pizzo,Vaccarob
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experimental part
p. 1218 - 1224
(2009/05/30)
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- PROTON PUMP INHIBITORS
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A proton pump inhibitor containing a compound represented by the formula (I) wherein X and Y are the same or different and each is a bond or a spacer having 1 to 20 carbon atoms in the main chain, R1 is an optionally substituted hydrocarbon group or an optionally substituted heterocyclic group, R2, R3 and R4 are the same or different and each is a hydrogen atom, an optionally substituted hydrocarbon group, an optionally substituted thienyl group, an optionally substituted benzo[b]thienyl group, an optionally substituted furyl group, an optionally substituted pyridyl group, an optionally substituted pyrazolyl group, an optionally substituted pyrimidinyl group, an acyl group, a halogen atom, a cyano group or a nitro group, R5 and R6 are the same or different and each is a hydrogen atom or an optionally substituted hydrocarbon group, which has a superior proton pump action and shows an antiulcer activity and the like after conversion to a proton pump inhibitor in the body, or a salt thereof. or a prodrug thereof is provided.
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- A convenient one-pot PCC oxidation-Wittig reaction of alcohols
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A simple one-pot process for the PCC oxidation of alcohols followed by in situ trapping of the aldehyde with a Wittig reagent is described.
- Bressette, Andrew R.,Glover IV, Louis C.
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p. 738 - 740
(2007/10/03)
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- Mild esterification and transesterification of carboxylic acids catalyzed by tetracyanoethylene and dicyanoketene dimethyl acetal
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A π-acid tetracyanoethylene (TCNE) and its derivative dicyanoketene dimethyl acetal (DCKDMA) were found to catalyze esterification of lauric acid with various types of alcohols. This method was successfully applied to methyl esterification of a variety of carboxylic acids including aromatic, α,β-unsaturated, α-hydroxy, and N-Cbz and N-Boc-protected α-amino acids without racemization at the range from room temperature to 60 °C. TCNE was also found to operate as a catalyst in transeslerification reaction of methyl laurate.
- Masaki, Yukio,Tanaka, Nobuyuki,Miura, Tsuyoshi
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- Wittig reactions in the presence of silica gel
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Wittig reactions, of stable phosphorous ylids, when carried out in presence of silica gel, in hexane, provide a fast, efficient and simple method to obtain α:β unsaturated compounds in high yields and high purity.
- Patil, Vijay J.,Maevers, Ursula
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p. 1281 - 1284
(2007/10/03)
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- Ruthenium-catalyzed oxidations for selective syntheses of ketones and acyl cyanides. Selective acylation of amino compounds with acyl cyanides
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Oxidation of alcohols to the corresponding carbonyl compounds with tert-butyl hydroperoxide in the presence of dichlorotris(triphenylphosphine)ruthenium catalyst gives the corresponding carbonyl compounds with high efficiency. This method can be applied to the oxidation of cyanohydrins to give acyl cyanides which are versatile synthetic intermediates. Acylation of amino compounds with acyl cyanides thus obtained proceeds chemoselectively. Thus, the reaction of amino alcohols with acyl cynides gives N-acylated products exclusively. In the similar N-acylation of polyamines primary amines are selectively acylated in the presence of secondary amines. These reactions are highly useful for the synthesis of spermidine and spermine alkaloids such as spermidine alkaloids such as spermidine siderophores. Dimeric cyclocoupling reaction of diacyl cyanides such as iso- and terephthaloyl cyanides with polyamines can be performed under the similar reaction conditions to give the corresponding polyazamacrocycles with high efficiency.
- Murahashi,Naota
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p. 433 - 440
(2007/10/02)
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- Enantioselective Diastereospecific Synthesis of anti-α-Alkyl-β-hydroxy Esters through Cuprate Opening of Glycidic Esters
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A diastereospecific chain elongation of the aldehydes 1 to anti-αalkyl-β-hydroxy esters 2 via the intermediates 4 - 7 is described.By means of the Sharpless epoxidation, 2 may be obtained with >90percent ee in either enantiomer.
- Mulzer, Johann,Lammer, Ortrud
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p. 2178 - 2190
(2007/10/02)
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- RUTHENIUM CATALYZED OXIDATION OF CYANOHYDRINS TO ACYL CYANIDES USEFUL REAGENTS FOR SELECTIVE N-BENZOYLATION OF AMINOALCOHOLS
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Ruthenium catalyzed oxidation of cyanohydrins with tert-butyl hydroperoxide gives the corresponding acyl cyanides in good to excellent yields.Acyl cyanides thus obtained are useful reagents for selective N-benzoylation of aminoalcohols.
- Murahashi, Shun-ichi,Naota, Takeshi,Nakajima, Nobuyuki
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p. 925 - 928
(2007/10/02)
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- On the Conjugative Isomerizations of β,γ-Unsaturated Esters. Stereochemical Generalizations and Predictions for 1,3-Prototropic Shifts under Basic Conditions
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An investigation of the base-catalyzed conjugative isomerization of a series of β,γ-unsaturated esters to their corresponding α,β-unsaturated esters was performed.It was found that, withh sodium hydride in THF, methyl 3-butenoate isomerized initially to a 5:1 ratio of (Z)- to (E)-methyl 2-butenoates; the Z:E ratio is time dependent, and after several days, the thermodynamic ratio 1:23 = Z:E was obtained.The isomerization appears to be catalytic in NaH, as it proceeds with less than 1 molar equiv of base, no hydrogen evolution is observed, and the reaction rate is approximately first order in NaH and zero order in ester.Under the same conditions (Z)-methyl 3-hexenoate isomerized stereoselectively to (E)-methyl 2-hexenoate while (E)-methyl 3-hexenoate isomerized to a 2:1 mixture of (Z)- and (E)-methyl 2-hexenoates.These product ratios are far from the isomeric compositions obtained under equilibrating conditions.To investigate further the stereochemical outcome of these isomerizations, three isomeric β,γ-unsaturated methyl esters were studied: (a) methyl 3-ethyl-3-butenoate isomerized exlusively to (E)-methyl 3-methyl-2-pentenoate; (b) (E)-methyl 3-methyl-3-pentenoate isomerized exlusively to (Z)-methyl 3-methyl-2-pentenoate; (c) (Z)-methyl 3-methyl-3-pentenoate isomerized exlusively to (E)-methyl 3-methyl-2-pentenoate.In the latter three cases, dimerization was not observed presumably due to steric effects.Related results were observed for a smaller series of β,γ-unsaturated amide isomerizations.Examination of the literature on olefin isomerizations reveals a general trend that the current results exemplify.Thus, in the absence of severe steric factors or cation-anion complexation, deprotonation at allylic positions kinetically preferentially forms the anion possessing a cisoid crotyl subunit (if available) regardless of initial substrate conformation.The stereochemical consequences of this results in E Z and Z E geometry conversions in kinetic 1,2-transpositions of olefins.This generalization can also be applied to the stereochemical results of ketone, ester, and hydrazone enolate formation, base-catalyzed exchange in polysubstituted aromatics and heteroaromatics, and other reactions involving the formation of allylic or benzylic anions.
- Alcock, Simon G.,Baldwin, Jack E.,Bohlmann, Rolf,Harwood, Laurence M.,Seeman, Jeffrey I.
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p. 3526 - 3535
(2007/10/02)
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- SYNTHESIS AND PHASE-TRANSFER MEDIATED ALKYLATIONS OF 2-DIETHYLAMINO-4-PHENYLSULFONYL-2-BUTENENITRILE AN EFFICIENT HOMOENOLATE EQUIVALENT
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The title compound is readily prepared from N-diethylacrylamide in three steps.Alkylation of 1 under phase-transfer conditions yields α-cyanoenamines 4 which can be transformed into saturated or unsaturated (α,β or β,γ) esters.
- Lombaert, Stephane De,Ghosez, Leon
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p. 3475 - 3478
(2007/10/02)
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- Selective γ- Alkylation of Copper Enolates Derived from α,β-Unsaturated Acids: Factors Affecting Scope and Regio- and Stereoselectivity
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Copper dienolates derived from α,β-unsaturated acids undergo alkylation at the γ-carbon with high regioselectivity.A systematic investigation has been made of several factors that affect the γ-alkylation process of the dienolate derived tiglic acid (1): alterations in the nature of the counterion, in the stoichiometry of cuprous ion, and in the nature of the electrophile.Compared to allylic electrophiles, nonallylic electrophiles react with copper dienolates sluggishly and with little selectivity for the γ-carbon; vinylic epoxides, however, are particularly goodalkylating agents.They undergo allylic transposition and react at the γ-carbon of the dienolate with high selectivity (70-90 percent), generating an allylic unit that forms part of a 1,5-diene skeleton oxygenated at both ends.Tiglic (1) and crotonic (3) acids react with vinylic epoxides to form a 1,5-diene with entirely E stereochemistry at the 2,3 double bond, while senecioic acid (2) forms a 1,5-diene with mostly Z stereochemistry at the 2,3 double bond.Geometry at the 6,7 double bond depends both on the α,β-unsaturated acid used and on the structure of the epoxide.With allylic electrophiles under direct (SN2) attack, stereochemical analysis showed that some isomerization occurs around the 6,7 double bond (derived from the electrophile).Addition of cuprous ion to the lithium dianion of 2-hexenoic acid (17) was found to enhance the regioselectivity of γ alkylation, but a subsequent Michael addition reaction limits the potential of γ alkylation in this system.
- Savu, Patricia M.,Katzenellenbogen, John A.
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p. 239 - 250
(2007/10/02)
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- Stereoselective Synthesis of α,β-Unsaturated Esters
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Reaction of α-silylated ester magnesium enolates with aldehydes affords exclusively one diastereoisomer of the two possible β-hydroxy silanes which give pure E-unsaturated esters on acid work-up.
- Larcheveque, Marc,Debal, Alain
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p. 877 - 878
(2007/10/02)
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