- Base-induced Sommelet–Hauser rearrangement of N-(α-(2-oxyethyl)branched)benzylic glycine ester-derived ammonium salts via a chelated intermediate
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The base-induced Sommelet–Hauser (S–H) rearrangement of N-(α-branched)benzylic glycine ester-derived ammonium salts 1 was investigated. When the α-branched substituent was a simple alkyl, such as a methyl or butyl, desired S–H rearrangement product 2 was obtained in low yield with formation of the [1,2] Stevens rearranged 4 and Hofmann eliminated products 5 and 6. However, when the α-branched substituent had a 2-oxy moiety, such as 2-acetoxyethyl or 2-benzoyloxyethyl, the yields of 2 were improved. These results could be explained by formation of chelated intermediate C that stabilizes the carbanionic ylide, and the subsequent initial dearomative [2,3] sigmatropic rearrangement would be accelerated. The existence of C was supported by mechanistic experiments. This enhancement effect is not very strong or effective; however, it will expand the synthetic usefulness of ammonium ylide rearrangements.
- Baba, Souya,Hirano, Kazuki,Tayama, Eiji
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supporting information
(2020/03/13)
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- Iridium-catalysed C-H borylation of β-aryl-aminopropionic acids
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Iridium-catalysed catalytic, regioselective C-H borylation of β-aryl-aminopropionic acid derivatives gives access to 3,5-functionalised protected β-aryl-aminopropionic acid boronates. The synthetic versatility of these new boronates is demonstrated through sequential one-pot functionalisation reactions to give diverse building blocks for medicinal chemistry. The C-H borylation is also effective for dipeptide substrates. We have exemplified this methodology in the synthesis of a pan αv integrin antagonist.
- MacDonald, Simon J. F.,Nortcliffe, Andrew,Robinson, Henry,Simelis, Klemensas,Stillibrand, Joe
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supporting information
p. 6696 - 6701
(2020/09/21)
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- Structure activity relationships of αv integrin antagonists for pulmonary fibrosis by variation in aryl substituents
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Antagonism of αvβ6 is emerging as a potential treatment of idiopathic pulmonary fibrosis based on strong target validation. Starting from an αvβ3 antagonist lead and through simple variation in the nature and position of the aryl substituent, the discovery of compounds with improved αvβ6 activity is described. The compounds also have physicochemical properties commensurate with oral bioavailability and are high quality starting points for a drug discovery program. Compounds 33S and 43E1 are pan αv antagonists having ca. 100 nM potency against αvβ3, αvβ5, αvβ6, and αvβ8 in cell adhesion assays. Detailed structure activity relationships with these integrins are described which also reveal substituents providing partial selectivity (defined as at least a 0.7 log difference in pIC50 values between the integrins in question) for αvβ3 and αvβ5.
- Adams, James,Anderson, Edward C.,Blackham, Emma E.,Chiu, Yin Wa Ryan,Clarke, Thomas,Eccles, Natasha,Gill, Luke A.,Haye, Joshua J.,Haywood, Harvey T.,Hoenig, Christian R.,Kausas, Marius,Le, Joelle,Russell, Hannah L.,Smedley, Christopher,Tipping, William J.,Tongue, Tom,Wood, Charlotte C.,Yeung, Jason,Rowedder, James E.,Fray, M. Jonathan,McInally, Thomas,Macdonald, Simon J. F.
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supporting information
p. 1207 - 1212
(2015/04/27)
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- Enantioselective acylation of β-phenylalanine acid and its derivatives catalyzed by penicillin G acylase from alcaligenes faecalis
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This study developed a simple, efficient method for producing racemic β-phenylalanine acid (BPA) and its derivatives via the enantioselective acylation catalyzed by the penicillin G acylase from Alcaligenes faecalis (Af-PGA). When the reaction was run at 25°C and pH 10 in an aqueous medium containing phenylacetamide and BPA in a molar ratio of 2:1, 8 U/mL enzyme and 0.1 M BPA, the maximum BPA conversion efficiency at 40 min only reached 36.1%, which, however, increased to 42.9% as the pH value and the molar ratio of phenylacetamide to BPA were elevated to 11 and 3:1, respectively. Under the relatively optimum reaction conditions, the maximum conversion efficiencies of BPA derivatives all reached about 50% in a relatively short reaction time (45-90 min). The enantiomeric excess value of product (eep) and enantiomeric excess value of substrate (ees) were all above 98% and 95%, respectively. These results suggest that the method established in this study is practical, effective, and environmentally benign and may be applied to industrial production of enantiomerically pure BPA and its derivatives.
- Li, Dengchao,Ji, Lilian,Wang, Xinfeng,Wei, Dongzhi
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p. 207 - 216
(2013/04/23)
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- Carica papaya lipase catalysed resolution of β-amino esters for the highly enantioselective synthesis of (S)-dapoxetine
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An efficient synthesis of the (S)-3-amino-3-phenylpropanoic acid enantiomer has been achieved by Carica papaya lipase (CPL) catalysed enantioselective alcoholysis of the corresponding racemic N-protected 2,2,2-trifluoroethyl esters in an organic solvent. A high enantioselectivity (E > 200) was achieved by two strategies that involved engineering of the substrates and optimization of the reaction conditions. Based on the resolution of a series of amino acids, it was found that the structure of the substrate has a profound effect on the CPL-catalysed resolution. The enantioselectivity and reaction rate were significantly enhanced by switching the conventional methyl ester to an activated trifluoroethyl ester. When considering steric effects, the substituted phenyl and amino groups should not both be large for the CPL-catalysed resolution. The mechanism of the CPL-catalysed enantioselective alcoholoysis of the amino acids is discussed to delineate the substrate requirements for CPL-catalysed resolution. Finally, the reaction was scaled up, and the products were separated and obtained in good yields (≥ 80 %). The (S)-3-amino-3- phenylpropanoic acid obtained was used as a key chiral intermediate in the synthesis of (S)-dapoxetine with very high enantiomeric excess (> 99 %). A carica papaya lipase catalysed resolution of N-protected β-phenylalanine esters has been developed. High enantioselectivity was achieved by two strategies that involved engineering of the substrates and optimization of the reaction conditions. After 50 % conversion, the products were separated and used as key chiral intermediates for the synthesis of (S)-dapoxetine with > 99 % ee. Copyright
- You, Pengyong,Qiu, Jian,Su, Erzheng,Wei, Dongzhi
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p. 557 - 565
(2013/03/13)
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- Phenylalanine aminomutase-catalyzed addition of ammonia to substituted cinnamic acids: A route to enantiopure α- and β-amino acids
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(Chemical Equation Presented) An approach is described for the synthesis of aromatic α- and β-amino acids that uses phenylalanine aminomutase to catalyze a highly enantioselective addition of ammonia to substituted cinnamic acids. The reaction has a broad scope and yields substituted α- and β-phenylalanines with excellent enantiomeric excess. The regioselectivity of the conversion is determined by substituents present at the aromatic ring. A box model for the enzyme active site is proposed, derived from the influence of the hydrophobicity of substituents on the enzyme affinity toward various substrates.
- Szymanski, Wiktor,Wu, Bian,Weiner, Barbara,De Wildeman, Stefaan,Feringa, Ben L.,Janssen, Dick B.
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supporting information; experimental part
p. 9152 - 9157
(2010/03/01)
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- Synthesis and anticonvulsant activity of some new hexahydropyrimidine-2,4- dione derivatives
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In this study, twelve new hexahydropyrimidine-2,4-dione derivatives were synthesized and screened for their anticonvulsant activities. All the compounds (7a-l) which have 6-arylhexahydropyrimidine-2,4-dione and N,N-disubstituted dithiocarbamate structures were prepared by the reaction with appropriate 3-(2-chloroethyl)-6-arylhexahydropyrimidine-2,4-diones and the corresponding N,N-disubstituted dithiocarbamate potassium salts. The structure of the synthesized compounds was confirmed by UV, IR, 1H-NMR and elemental analysis. Their anticonvulsant activities were determined by maximal electroshock (MES), subcutaneous pentetrazol (metrazol, scMet) and rotorod toxicity tests for neurological deficits. According to the activity studies, 6-(4-chlorophenyl)hexahydropyrimidine-2,4-dione derivatives (7e-h) were found to be highly protective against MES and scMet. Neurotoxicity was not observed in any of the tested compounds.
- Septioglu, Ebubekir,Aytemir, Mutlu Dilsiz,Calis, Uensal
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p. 259 - 264
(2007/10/03)
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- A convenient synthesis of dihydro- and tetrahydro-1,3-thiazine derivatives from β-aryl-β-amino acids
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A facile synthesis of 2-alkyl-4-aryl-5,6-dihydro-4H-1,3-thiazines and cis-2-alkyl-4-aryl-3,4,5,6-tetrahydro-2H-1,3-thiazines with potential therapeutic interest was achieved starting from readily accessible β-aryl-β-amino acids.
- Leflemme, Nicolas,Dallemagne, Patrick,Rault, Sylvain
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p. 1503 - 1505
(2007/10/03)
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- 1-aza-2-alkyl-6-aryl-cycloalkane compounds
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Compound of formula (I): wherein: n represents 0 or 1, R1represents hydrogen, arylalkyl, alkyl, acyl, alkoxycarbonyl, arylalkoxycarbonyl or trifluoroacetyl, R2represents alkyl, X represents oxygen, chlorine, OR3, SR4
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