- Studies on stereoselective [2+2] cycloadditions between N,N-dialkylhydrazones and ketenes
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Staudinger-like cycloadditions between chiral, non-racemic N,N-dialkylhydrazones 1 and functionalized ketenes constitute an efficient methodology for the stereoselective construction of the β-lactam ring. The potential for fine tuning of the dialkylamino
- Martin-Zamora, Eloisa,Ferrete, Ana,Llera, Jose M.,Munoz, Jesus M.,Pappalardo, Rafael R.,Fernandez, Rosario,Lassaletta, Jose M.
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p. 6111 - 6129
(2007/10/03)
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- Stereoselective cyanation of chiral α-amino aldehydes by reaction with Nagata's reagent: A route to enantiopure β-amino-α-hydroxy acids
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Chiral α-dibenzylamino aldehydes react with diethylaluminum cyanide leading to anti-β-dibenzylamino-α-hydroxycyanides as the major diastereoisomers in good yields and diastereomeric excesses. Hydrolysis of the nitrile derivatives allows the synthesis of enantiopure β-amino-α-hydroxy acids.
- Andres, Jose M.,Martinez, Maria A.,Pedrosa, Rafael,Perez-Encabo, Alfonso
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p. 347 - 353
(2007/10/03)
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- Enantiospecific and diastereoselective synthesis of syn-β-amino-α-hydroxy acids
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The reaction of chiral α-hydroxy β,γ-unsaturated esters with tosyl isocyanate followed by cyclization of the resulting allylic carbamates with iodine in the presence of sodium carbonate provided trans-4,5-disubstituted 2-oxazolidinone derivatives in a highly diastereoselective manner. The subsequent removal of the iodo group and the protective functionality afforded the syn-β-amino-α-hydroxy acids. Using the reaction sequence, (2R,3S)- and (2S,3R)-3-amino-2-hydroxy acids were synthesized with high enantioselectivity.
- Sugimura, Hideyuki,Miura, Masayuki,Yamada, Nobuko
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p. 4089 - 4099
(2007/10/03)
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- Histidine derivatives
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Novel amino acid derivatives useful as a therapeutic agent are disclosed. These amino acid derivatives and the pharmaceutically acceptable salts thereof have a human renin inhibitory effect when administered orally and are useful for treatment of hypertension, especially renin-associated hypertension.
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- Novel amino acid derivatives
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Novel amino acid derivatives useful as a therapeutic agent are disclosed. These amino acid derivatives and the pharmaceutically acceptable salts thereof have a human renin inhibitory effect when administered orally and are useful for treatment of hypertension, especially renin-associated hypertension.
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- Renin Inhibitors. Substitution of the Leucyl Residues of Leu-Leu-Val-Phe-OCH3 with 3-Amino-2-hydroxy-5-methylhexanoic Acid
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The 2S,3S and 2R,3S diastereoisomers of the hydroxy amino acid 3-amino-2-hydroxy-5-methylhexanoic acid (AHMHA) were synthesized and substituted for the leucyl residues of Leu-Leu-Val-Phe-OCH3 to yield the following analogues: AHMHA-Leu-Val-Phe-OCH3, AHMHA
- Johnson, Rodney L.
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p. 605 - 610
(2007/10/02)
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- Synthesis of (2S,3R)-3-Amino-2-hydroxy-5-methylhexanoic Acid Derivatives. Application to the Synthesis of Amastatin, an Inhibitor of Aminopeptidases
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Methods are reported for the synthesis of optically pure derivatives of (2S,3R)-3-amino-2-hydroxy-5-methylhexanoic acid. -D-leucine methyl ester was reduced in 95percent yield with diisobutylaluminum hydride to the aldehyde which was converted via the cyanohydrin to (2RS,3R)-3-amino-2-hydroxy-5-methylhexanoic acid (AHMHA).The mixture of diastereomers was converted to the corresponding Boc-AHMHA methyl ester derivatives and separated by chromatography over silica gel.The optical purity of the diastereomers at C-3 was established by converting each to diastereomeric Boc-AHMHA-Leu-OMe and separating these dipeptides by chromatography.Pure (2S,3R)-Boc-AHMHA was coupled with valyl-valyl-aspartic acid dibenzyl ester by using dicyclohexylcarbodiimide/ 1-hydroxybenzotriazole in 63percent yield.The Boc group was removed by using trifluoroacetid acid, and the benzyl groups were removed by hydrogenolysis.The product, (2S,3R)-AHMHA-L-Val-L-Val-L-Asp, amastatin, was found to be identical with the natural product.
- Rich, Daniel H.,Moon, Byung Jo,Boparai, Amrit S.
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p. 2288 - 2290
(2007/10/02)
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