- Rapid and efficient microwave-assisted synthesis of N-carbamoyl-L-amino acids
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A rapid and efficient method for the synthesis of N-carbamoyl-L-amino acids is reported. The procedure, involving the reaction between urea and α-amino acids sodium salts, was performed under microwave conditions using an unmodified domestic microwave oven. A careful study of the operative conditions indicated proline (1d) as the less reactive substrate and phenylglycine (1e) as the more reactive one among all the α-amino acids tested. Substitution of urea with potassium cyanate produced a low conversion into the corresponding N-carbamoyl derivative, and a possible explanation of this result is reported. Copyright Taylor & Francis Group, LLC.
- Verardo, Giancarlo,Geatti, Paola,Strazzolini, Paolo
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p. 1833 - 1844
(2008/02/02)
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- Palladium-catalyzed synthesis of substituted hydantoins - A new carbonylation reaction for the synthesis of amino acid derivatives
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One-step synthesis of substituted hydantoins can be achieved by the palladium-catalyzed 'ureidocarbonylation' of aldehydes with urea derivatives and carbon monoxide [Eq. (1)]. This surprisingly selective protocol converts substituted ureas into 1,5- and 1,3,5-substituted hydantoins in yields of up to 93 %.
- Beller, Matthias,Eckert, Markus,Moradi, Wahed A.,Neumann, Helfried
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p. 1454 - 1457
(2007/10/03)
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- New hydantoinases from thermophilic microorganisms - Synthesis of enantiomerically pure D-amino acids
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A series of 14 D-α-amino acids were prepared in high chemical and optical yields from the corresponding racemic hydantoins by employing two novel hydantoinases from thermophilic microorganisms.
- Keil,Schneider,Rasor
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p. 1257 - 1260
(2007/10/02)
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- PRACTICAL SYNTHESIS OF OPTICALLY ACTIVE α-HYDRAZINO ACIDS FROM α-AMINO ACIDS
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Simple amino acids (1) can be converted in fair to good yield into hydrazino acids (3) of like configuration by using KOCl instead of NaOCl to promote the Shestakov rearrangement of the intermediate hydantoic acids (2).
- Viret, Joelle,Gabard, Jacqueline,Collet, Andre
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p. 891 - 894
(2007/10/02)
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- Mechanism of Asymmetric Production of D-Amino Acids from the Corresponding Hydantoins by Pseudomonas sp.
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The mechanism of asymmetric production of D-amino acids from the corresponding hydantoins by Pseudomonas sp.AJ-11220 was examined by investigating the properties of the enzymes involved in the hydrolysis of DL-5-substituted hydantoins.The enzymatic production of D-amino acids from the corresponding hydantoins by Pseudomonas sp.AJ-11220 involved the following two successive reactions; the D-isomer specific hydrolysis, i.e., the ring opening of D-5-substituted hydantoins to D-form N-carbamyl amino acids by an enzyme, D-hydantoin hydrolase (D-HYD hydrolase), followed by the D-isomer specific hydrolysis, i.e., the cleavage of N-carbamyl-D-amino acids to D-amino acids by an enzyme, N-carbamyl-D-amino acid hydrolase (D-NCA hydrolase).L-5-Substituted hydantoins not hydrolyzed by D-HYD hydrolase were converted to D-form 5-substituted hydantoins through spontaneous racemization under the enzymatic reaction conditions.It was proposed that almost all of the DL-5-substituted hydantoins were stoichiometrically and directly converted to the corresponding D-amino acids through the successive reactions of D-HYD hydrolase and D-NCA hydrolase in parallel with the spontaneous racemization of L-5-substituted hydantoins to those of DL-form.
- Yokozeki, Kenzo,Kubota, Koji
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p. 721 - 728
(2007/10/02)
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- Preferential Cryatallization of 2-Amino-2-phenylethanol and Its Application as a Resolving Agent
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(+/-)-2-Amino-2-phenylethanol (phenylglycinol) prepared from (+/-)-2-amino-2-phenylacetic acid (DL-phenylglycine) by lithium aluminium hydride reduction was efficiently resolved into a pair of optically active forms by preferential crystallization.The optically active amino alcohol was successfully applied as a basic resolving agent to the resolution of tartaric acid, 2-hydroxy-2-phenylpropionic acid, 2-hydroxy-3-phenylpropionic acid, 2-phenylpropionic acid, and 2-phenyl-2-ureidoacetic acid.
- Saigo, Kazuhiko,Miura, Hisao,Ishizaki, Kozi,Nohira, Hiroyuki
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p. 1188 - 1190
(2007/10/02)
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- Synthesis of Optically Active Spirohydantoins by Asymmetric Induction. Hydantoin Formation from Amino Nitriles and Chlorosulfonyl Isocyanate
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Conversion of 6-chloro- or 6-fluoro-2,3-dihydro-4H-1-benzopyran-4-one with optically active (S)-α-methylbenzylamine in the presence of TiCl4 to the ketimine followed by treatment in EtOH with HCN gas gives excellent yields of crystalline, enantiomerically pure (4S)-4-cyano-2,3-dihydro-6-chloro(or 6-fluoro)-4--4H-1-benzopyran.These sterically hindered amino nitriles react smoothly with chlorosulfonyl isocyanate to give, after hydrolysis, the hydantoins (4S)-2,3-dihydro-6-chloro(or 6-fluoro)-3'-spiro-2',5'-dione.The α-methylbenzyl groups can be removed by aqueous HBr/acetic acid to give the unprotected spirohydantoins.
- Sarges, Reinhard,Howard, Harry R.,Kelbaugh, Paul R.
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p. 4081 - 4085
(2007/10/02)
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