Asymmetric synthesis of 3-amino-2-hydroxy-4-phenylbutanoate

Asymmetric synthesis of 3-amino-2-hydroxy-4-phenylbutanoate, a key component of the natural product bestatin and HIV protease inhibitors of KNI-272 and R-87366, has been achieved from the stereoselective aldimine coupling reaction between 3-phenyl-2-aminopropanenitrile and (Z)-α-methoxy trimethylsilyl ketene acetal in the presence of Lewis acids.     

Rapid and efficient synthesis of 2-amino-4H-benzothiazines

The benzothiazine nucleus is a relatively unexplored class of compounds, from the standpoint of both synthetic chemistry and biological activity. We have developed a rapid, high-yielding synthesis of benzothiazines in which a precursor aryl thiourea is prepared on solid phase. Addition of trifluoroacetic acid catalyzes a conjugate addition reaction to form the desired heterocycle and releases it from the resin.     

Highly efficient enantioselective three-component synthesis of 2-amino-4H-chromenes catalysed by chiral tertiary amine-thioureas

A three-component cascade reaction of salicylaldehyde, malononitrile/cyanoacetate and nitromethane catalysed by chiral tertiary amino-thioureas was developed, which leads to the production of highly functionalized 2-amino-4H-chromenes in good yields with good to excellent enantioselectivities.     

Highly enantioselective hydrogenation of 2-oxo-4-arybutanoic acids to 2-hydroxy-4-arylbutanoic acids

The Ru-catalyzed asymmetric hydrogenation of 2-oxo-4-arybutanoic acids to afford 2-hydroxy-4-arybutanoic acids was accomplished by employing SunPhos as chiral ligand and 1 M aq HBr as additive. The high enantioselectivities (88.4%-92.6% ee) and efficiency (TON=10,000, TOF=300 h⁻¹) make this method efficient for the synthesis of an important intermediate, (R)-2-hydroxy-4-phenylbutanoic acid, for ACE inhibitors.     

Ca(OH)2-mediated efficient synthesis of 2-amino-5-hydroxy-4H-chromene derivatives with various substituents

A variety of novel 2-amino-5-hydroxy-4H-chromene derivatives with various substituents on the 4H-chromene ring were efficiently synthesized by one-pot reactions of substituted resorcinols and various 2-benzylidenemalononitriles in the presence of calcium hydroxide in methanol at room temperature. This simple method provided 2-amino-5-hydroxy-4H-chromenes with high yields under mild reaction conditions.     

Amino-functionalized SBA-15 catalyzed one-step synthesis of 2-amino-5-cyano-4-hydroxy-6-aryl pyrimidines

A simple and efficient approach towards one-step synthesis of 2-amino-5-cyano-4-hydroxy-6-aryl pyrimidines has been developed. It is based on three-component condensation of aliphatic, aromatic or heterocyclic aldehydes, ethyl cyanoacetate and guanidinium carbonate in the presence of amino-functionalized SBA-15 catalyst in ethanol. In this chemical process, the tautomeric interconversion of pyrimidine derivatives has been observed. This efficient technique has the advantage to give 2-amino-pyrimidine derivatives using a heterogeneous catalyst in high yields, to be completed in short reaction times and to offer a simple product isolation procedure.     

Complex formation equilibria between 1-hydroxy-7-sulpho-2-naphthoic or 1-hydroxy-4,7-disulpho-2-naphthoic acid and iron(III) in 0.1M NaClO4 medium

The equilibria for formation of iron(III) complexes with 1-hydroxy-7-sulpho-2-naphthoic and 1-hydroxy-4,7-disulpho-2-naphthoic acids in aqueous 0.1M sodium perchlorate medium at 25 degrees have been studied by spectrophotometric and potentiometric methods. The data are well described in terms of a series of stepwise complexes, FeL((3-rn)+)(r) in both systems (L(n-) denotes the unprotonated ligand anion).     

The synthesis of 1-amino-2-hydroxy- and 2-amino-1-hydroxy-substituted ethylene-1,1-bisphosphonic acids and their N-methylated derivatives

A synthesis of 2-amino-1-hydroxyethylene-1,1-bisphosphonic acid 3 has been developed from N-phthaloylglycine via dimethyl 2-(N-phthaloylamino)acetylphosphonate 1. The preparation of the N-methylated and N,N-dimethylated derivatives 4 and 5 has been achieved by the reaction of 3 with formic acid and formaldehyde. The synthesis of 1-amino-2-hydroxyethylene-1,1-bisphosphonic acid 9 (R=R′=H) and its N-methylated and N,N-dimethylated analogues has been achieved by the reaction of phosphorus trichloride and phosphorous acid with the appropriate O-benzyl protected hydroxyacetamide, followed by catalytic hydrogenolysis of the protecting group.     

Stereospecific synthesis of new 4-amino-1,2,3-cyclohexanetricarboxylic acids and 4-amino-1,3-cyclohexanedicarboxylic acids

Diels-Alder adducts of 1,2-dihydropyridine with maleic and acrylic acid derivatives were stereospecifically converted by way of RuO4 oxidation into new 4-amino-1,2,3-cyclohexanetricarboxylic acids and 4-amino-1,3-cyclohexanedicarboxylic acids.     

Facile synthesis of 5-amino- and 7-amino-6-azaoxindole derivatives

An efficient approach for the formation of 5-amino- and 7-amino-6-azaoxindole derivatives was developed. 2-Amino-4-chloro-3-nitropyridine (8), and its 5-nitro-substituted regioisomer (9), respectively, were obtained by reaction with ethyl malonate. The resulting 2-amino-3/5-nitropyridine derivatives substituted in the 4-position with malonic acid diethyl ester (10, 11) were subjected to reductive cyclization yielding 3-ethoxycarbonyl-6-azaoxindole derivatives 4a and 5a. Protection of the amino function was not required. Intermediates 10 and 11 could also be converted to the corresponding 4-acetic acid ethyl esters 12 and 13 by dealkoxycarbonylation with LiCl, and subsequently cyclized under reductive conditions yielding 3-unsubstituted 5-/7-aminooxazindoles.     

An efficient and facile synthesis of novel substituted pyrimidine derivatives: 4-amino-5-carbonitrile-2-nitroaminopyrimidine

One-pot, multicomponent reaction for the synthesis of novel substituted pyrimidine derivatives: 4-amino-5-carbonitrile-2-nitroaminopyrimidine from aromatic aldehydes, 1-nitroguanidine, and malononitrile under ethanol is described. Because of containing many active functional groups, such as amino, cyan and nitro, these products are important intermediate of organic synthesis. The advantages of this procedure include the short reaction time, mild reaction conditions, and excellent yields.     

Sodium 4-amino-5-hydroxy-7-sulfonaphthalene-2-sulfonate an efficient ligand for click reaction in water: Synthesis of 1,2,3-triazole pharmacophore linked-quinazolinone scaffold

Water soluble sodium 4-amino-5-hydroxy-7-sulfonaphthalene-2-sulfonate ligand was used successfully for the preparation of 1,2,3-triazoles pharmacophore linked-quinazolinone scaffold. The reaction of ethyl 4-oxo-3,4-dihydroquinazoline-2-carboxylate and related amide compounds with propargyl bromide afforded ethyl 4-oxo-3-(prop-2-yn-1-yl)-3,4-dihydroquinazoline-2-carboxylate and its amide derivatives. The reaction of propargylated compounds with azides catalyzed by copper (II) salt, in the presence of Sodium 4-amino-5-hydroxy-7-sulfonaphthalene-2-sulfonate as a ligand in water produced novel 1,2,3-triazole pharmacophore linked-quinazolinone-4-one scaffold with high-to-excellent yields. The ligand assisted in the click reaction and reduced loading of copper salt to 2 mol%. Simplicity, short reaction times, use of water as green solvent, and low catalyst loading are the main advantages of this procedure.     

Spectrophotometric determination of iron with 1-hydroxy-4-sulpho-2-naphthoic acid

1-Hydroxy-4-sulpho-2-naphthoic acid (H(3)L) is proposed as a spectrophotometric reagent for determination of iron. It gives a red-brown chelate, FeL(6-)(3), with lambda(max) 500-520 nm at pH 8 ( = 3.3 x 10(3) l. mole(-1). cm(-1)). In this wavelength region the reagent has no absorption. Most common cations and oxo-anions do not interfere. In the determination of iron in polymetallic iron ores and aluminium alloys the relative error and relative standard deviation of the method were found to be better than 1 and 0.5%, respectively. 1-Hydroxy-4-sulpho-2-naphthoic acid seems to be a more sensitive and accurate reagent for iron than 5-sulphosalicylic acid, and the number of interfering ions is smaller than in the 1,10-phenanthroline or thiocyanate methods.     

Synthesis of 2-amino-4-hydroxy-1,3,5-triazanaphthalenes

The synthesis of 2-amino-4-hydroxy-6-amyl-1,3,5-triazanaphthalene (8) is described as a model sequence pertinent to preparation of 8-deazafolic acid and its analogs. Condensation of 2-acet-amido-4-hydroxy-6-pyrimidinealdehyde (3) with dimethyl 2-oxoheptylphosphonate afforded 1-(2′-acetamido-4′-hydroxy-6′-pyrimidinyl)-1-octene-3-one (4) as a key intermediate. Conversion of 4 to 1-(2′-amino-4′-hydroxy-5′ -phenylazo-6′ pyrimidinyl)-3-octanone (7) followed by reductive cyclization yielded 8 or its tetrahydro derivative (9) .     

Traceless solid-phase synthesis of 2-amino-5-alkylidene-thiazol-4-ones

2-Amino-5-alkylidene-thiazol-4-ones bearing two diversity points are prepared by a solid-phase strategy exploiting rhodanine as the starting material. Rhodanine is first loaded on bromo-Wang resin, subjected to Knovenagel condensation with aldehydes, and cleaved off the resin in a traceless manner by means of an amine.     

A convenient synthesis of 2-substituted 4-amino-5-pyrimidinecarbonitriles

Synthesis of the novel 2-halogenated 4-amino-5-pyrimidinecarbonitriles 3a,b starting from ethoxy-methylenemalononitrile 1 and cyanamide is described. Nucleophilic substitution of the reactive halogen atom leads to the derivatives 5a-g, 6 and 7a-h.     

Synthesis of 4-hydroxy- and 3-aryl-4-amino- 2-trifluoromethylpyridines

Schemes for synthesizing 3-acyl-4-amino(hydroxy)-2-trifluoromethylpyridines from 3-acyl 4-amino-5,5,5-trifluoro-3-penten-2-ones via their diphenylboron chelate complexes have been suggested.Translated fromlzvestiyn Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2715–2718, November, 1996,     

A short efficient synthesis of 4-amino-2,3-dihydrobenzofuran

A new, practical synthesis of 4-amino-2,3-dihydrobenzofuran is described. Chlorination and a Sandmeyer reaction of the title compound are also reported.