- Utilization of (18-Crown-6)-2,3,11,12-tetracarboxylic Acid as a Chiral NMR Solvating Agent for Diamines and β-Amino Acids
-
The compound (18-crown-6)-2,3,11,12-tetracarboxylic acid was evaluated as a chiral nuclear magnetic resonance (NMR) solvating agent for a series of diamines and bicyclic β-amino acids. The amine must be protonated for strong association with the crown ether. An advantage of (18-crown-6)-2,3,11,12-tetracarboxylic acid over many other crown ethers is that it undergoes a neutralization reaction with neutral amines to form the protonated species needed for binding. Twelve primary diamines in neutral and protonated forms were evaluated. Diamines with aryl and aliphatic groups were examined. Some are atropisomers with equivalent amine groups. Others have two nonequivalent amine groups. Association equilibria for these systems are complex, given the potential formation of 2:1, 1:1, and 1:2 crown-amine complexes and given the various charged species in solution for mixtures of the crown ether with the neutral amine. The crown ether produced enantiomeric differentiation in the 1H NMR spectrum of one or more resonances for every diamine substrate. Also, a series of five bicyclic β-amino acids were examined and (18-crown-6)-2,3,11,12-tetracarboxylic acid caused enantiomeric differentiation in the 1H NMR spectrum of three or more resonances of each compound. Chirality 27:708-715, 2015.
- Rodriguez, Yolanda C.,Duarte, Tayla M.,Szakonyi, Zsolt,Forr?, Eniko,Fül?p, Ferenc,Wenzel, Thomas J.
-
p. 708 - 715
(2015/10/12)
-
- Bioresolution production of (2R,3S)-Ethyl-3-phenylglycidate for chemoenzymatic synthesis of the taxol C-13 side chain by galactomyces geotrichum ZJUTZQ200, a new epoxide-hydrolase-producing strain
-
A newly isolated Galactomyces geotrichum ZJUTZQ200 strain containing an epoxide hydrolase was used to resolve racemic ethyl 3-phenylglycidate (rac-EPG) for producing (2R,3S)-ethyl-3-phenylglycidate ((2R,3S)-EPG). G. geotrichum ZJUTZQ200 was verified to be able to afford high enantioselectivity in whole cell catalyzed synthesis of this chiral phenylglycidate synthon. After the optimization of the enzymatic production and bioresolution conditions, (2R,3S)-EPG was afforded with high enantioselectivity (e.e.S > 99%, E > 49) after a 8 h reaction. The co-solvents, pH buffer solutions and substrate/cell ratio were found to have significant influences on the bioresolution properties of G. geotrichum ZJUTZQ200. Based on the bioresolution product (2R,3S)-EPG, taxol's side chain ethyl (2R,3S)-3-benzoylamino-2-hydroxy- 3-phenylpropionate was successfully synthesized by a chemoenzymatic route with high enantioselectivity (e.e.S > 95%).
- Wei, Chun,Ling, Jinlong,Shen, Honglei,Zhu, Qing
-
p. 8067 - 8079
(2014/07/08)
-
- Rhodium-catalyzed enantioseletive hydrogenation of tetrasubstituted α-acetoxy β-enamido esters: A new approach to chiral α-hydroxyl-β-amino acid derivatives
-
Asymmetric hydrogenation of tetrasubtitued α-acetoxy β-enamido esters with rhodium catalysts based on chiral diphosphine ligands provides an efficient and concise route to the synthesis of chiral α-hydroxyl-β-amino acid derivatives in excellent enantioselectivities. The products are valuable chiral building blocks in many biologically active compounds and have important applications in organic synthesis.
- Wang, Qingli,Huang, Wenhua,Yuan, Haoquan,Cai, Qin,Chen, Liming,Lv, Hui,Zhang, Xumu
-
p. 16120 - 16123
(2015/02/18)
-
- PROCESS FOR PREPARING (2R, 3S) 2-BENZYLOXY-3-TERT-BUTOXY CARBONYL AMINO-3-PHENYL PROPIONIC ACID
-
A method for preparing(2R,3S)-2-benzyloxy-3-tert-butoxy-carbonylamino-3-phenylpropionic acid of formula (I) is provided, and a method for purifying and isolating the compound is also provided. The method uses inexpensive, non-hazardous and easily available reagents and results in better yields and purity.
- -
-
Page/Page column 9; 11
(2012/09/21)
-
- Highly diastereoselective and enantioselective synthesis of α-hydroxy β-amino acid derivatives: Lewis base catalyzed hydrosilylation of α-acetoxy β-enamino esters
-
By design: A series of α-acetoxy-β-enamino esters 1 were synthesized and then subjected to catalytic asymmetric hydrosilylation. In the presence of a chiral Lewis base catalyst, the reactions proceeded smoothly to provide a wide range of chiral α-acetoxy β-amino acid derivatives in high yields with good diastereoselectivities and enantioselectivities. Copyright
- Jiang, Yan,Chen, Xing,Zheng, Yongsheng,Xue, Zhouyang,Shu, Chang,Yuan, Weicheng,Zhang, Xiaomei
-
p. 7304 - 7307
(2011/09/16)
-
- A new enzymatic strategy for the preparation of (2R,3S)-3-phenylisoserine: a key intermediate for the Taxol side chain
-
Burkholderia cepacia lipase PS-IM catalysed the hydrolysis of racemic ethyl 3-amino-3-phenyl-2-hydroxypropionate with excellent enantioselectivity (E >200), when the reaction was performed with added H2O as a nucleophile, in iPr2O, at 50 °C. The hydrolysis of the less reactive enantiomeric ethyl 3-amino-3-phenyl-2-hydroxypropionate with 18% HCl afforded the corresponding enantiomerically pure (2R,3S)-3-amino-3-phenyl-2-hydroxypropionic acid hydrochloride, a key intermediate for the Taxol side chain.
- Forro, Eniko,Fueloep, Ferenc
-
scheme or table
p. 637 - 639
(2010/08/03)
-
- 1,3-Dipolar cycloadditions of carbonyl ylides to aldimines: A three-component approach to syn-α-hydroxy-β-amino esters
-
(Chemical Equation Presented) A highly diastereoselective Rh II-catalyzed 1,3-dipolar cycloaddition leads to the formation of syn-β-amino alcohols and syn-α-hydroxy-β-amino acids in high yields (see scheme; p-TSA = poro-toluenesulfonic acid, Bn = benzyl). This three-component approach to the addition of metal-associated carbonyl ylides to aldimines was applied to a short enantioselective synthesis of the C13 side chain of taxol.
- Torssell, Staffan,Kienle, Marcel,Somfai, Peter
-
p. 3096 - 3099
(2007/10/03)
-
- Synthesis of taxol, analogs and intermediates with variable A-nng side chains
-
An efficient protocol for the synthesis of taxol, taxol analogs, and their intermediates is described. The process includes the attachment of the taxol A-ring side chain to baccatin III and for the synthesis of taxol and taxol analogs with variable A-ring side chain structures. A rapid and highly efficient esterification of O-protected isoserine and 3-phenylisoserine acids having N-benzyoloxycarbonyl groups to the C-13 hydroxyl of 7-O-protected baccatin III is followed by a deprotection-acylation sequence to make taxol, calphalomanninne and various analogs, including photoaffinity labeling candidates.
- -
-
-
- Improved protection and esterification of a precursor of the taxotere and taxol side chains
-
(4S,5R)-N-BOC-2,2-dimethyl-4-phenyl-5-oxazolidinecarboxylic acid 8 was prepared and efficiently esterified by conveniently protected baccatins 9a,b. Smooth deprotection in formic acid gave the N-deprotected intermediates of Taxotere and taxol. This protocol did not generate any epimerization at C-2′ and constitutes a pratical method to prepare Taxotere, taxol and analogs.
- Commercon,Bezard,Bernard,Bourzat
-
p. 5185 - 5188
(2007/10/02)
-
- Synthesis of β-amino α-hydroxy carboxylic esters from oxiranecarboxylic esters
-
3-Aryl-3-azido-2-hydroxypropanoic esters, prepared from the corresponding 3-aryl-oxirane-2-carboxylic esters by ring opening with sodium azide, were reduced with tin(II) chloride dihydrate in methanol to give 3-amino-3-aryl-2-hydroxypropanoic esters in good yields.Under these conditions, halogen substituents in the aromatic rings were not affected.The nitro group, however, was partially reduced to the amino group.Treatment of aliphatic oxirane-2-carboxylic esters with acetonitrile in the presence of boron trifluoride etherate led to regiospecific formation of 2,4-dialkyl-2-oxazoline-5-carboxylic esters, resulting from reaction of the nitrile at C3.Acidic hydrolysis of these oxazoline-5-carboxylic esters gave the corresponding 3-(acylamino)-2-hydroxy carboxylic esters.With these two complementary methods, both aryl- and alkyl-substituted β-amino α-hydroxy acid derivatives are accessible.
- Legters, Johan,Dienst, Erik van,Thijs, Lambertus,Zwanenburg, Binne
-
-
- CHEMO-ENZYMATIC SYNTHESIS OF ALL ISOMERIC 3-PHENYLSERINES AND -ISOSERINES
-
The synthesis of all isomers of 3-phenylserines and 3-phenylisoserines in enantiomerically pure form is presented.Diastereomerically pure educts (threo/erythro-2-azido-3-butanoyloxy-3-phenyl-propionic esters, threo/erythro-3-azido-2-butanoyloxy-3-phenylpropionic esters, threo-2-butanoylamino-3-butanoyloxy-3-phenylpropionic ester, erythro-3-butanoylamino-2-butanoyloxy-3-phenyl-propionamide) were prepared from cinnamic acid derivatives or via aldol condensations of benzaldehyde and suitable enolates in few steps.These racemates were resolved with lipases from Candida cylindracea (CC) and Pseudomonas fluorescens (P) and the obtained products were hydrogenated to 3-phenylserines and -isoserines.The influence of the acyl group in the enzymatic resolution of erythro-3-azido-2-acyloxy-3-phenylpropionic esters was investigated.
- Hoenig, H.,Seufer-Wasserthal, P.,Weber, H.
-
p. 3841 - 3850
(2007/10/02)
-