An expedient synthesis of (±)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid hydrobromide via a 3-bromoisoxazole intermediate

The excitatory, amino acid ±2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid hydrobromide was prepared in gram quantities in an 3.3% overall yield from methylbut 2-ynoate. The key step was the facile preparation of methyl 3-bromo-5-methylisoxazole-4-carboxylate.     

Synthesis and biological evaluation of novel 9-heteroaryl substituted 7-chloro-4,5-dihydro-4-oxo-1,2,4-triazolo[1,5-a]quinoxaline-2-carboxylates (TQX) as (R,S)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) receptor antagonists

In this paper, we report a study on some new 4,5-dihydro-4-oxo-1,2,4-triazolo[1,5-a]quinoxaline-2-carboxylate derivatives (TQXs), bearing a nitrogen-containing heterocycle at position-9, and designed as (R,S)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA) receptor antagonists. These compounds ensue from the structural modification of previously reported 8-heteroaryl-TQXs which were endowed with high affinity and selectivity for the AMPA receptor. All the newly synthesized compounds were biologically evaluated for their binding at the AMPA receptor. Gly/N-methyl-D-aspartic acid (NMDA) and kainic acid (KA) high-affinity binding assays were performed to assess the selectivity of the reported derivatives toward the AMPA receptor. This study produced some new TQXs which are less potent than the reference compounds, and endowed with a mixed AMPA and Gly/NMDA receptor binding affinity. To rationalize the experimental findings, a molecular modeling study was performed by docking some TQX derivatives to the AMPA receptor model.     

Synthesis of thiopyrano[2,3-d] pyrimidines and thieno[2,3-d]pyrimidines

The reaction of 4-chloro-5-cyano-2-methylthiopyrimidine (I) with ethyl mercaptosuccinate (II) in refluxing ethanol containing sodium carbonate has afforded diethyl 3-amino-2-(methyl-thio)-7H-thiopyrano[2,3-d]pyrimidine-6,7-dicarboxylate (IV). Displacement of the methylthio group in IV with hydrazine gave the corresponding hydrazino derivative which underwent Schiff base formation with benzaldehyde or 2,6-dichlorobenzaldehyde. Treatment of IV in refluxing acetic anhydride afforded the corresponding diacetylated amino derivative. Partial saponification of IV with sodium hydroxide gave 5-amino-2-(methylthio)-7H-thiopyrano-[2,3-d]pyrimidine 6,7-dicarboxylic acid 6 ethyl ester (VIII). The reaction of 4-amino-6-chloro-5-cyano-2-phenylpyrirnidine (XI) with II resulted in the formation of ethyl 4-amino-6-(ethoxy-carbonyl)-5,6-dihydro-5-amino-2-phenylthieno[2,3-d]pyrimidine-6-acetate (XIII) which when subjected to hydrolysis gave ethyl 4,5-diamino-2-phenylthieno[2,3-d]pyrimidine-6-acetate isolated as the hydrochloride (XIV). Diazotization of IV with sodium nitrite in acetic acid unexpectedly afforded diethyl 5-(acetyloxy)-6,7-dihydro-6-hydroxy-2-(methylthio)-5H-thio-pyrano[2,3-d]pyrimidine-6,7-diearboxylate (XV). Several structural ambiguities were resolved by ir and pmr spectra.     

Preparation of aminotriazole-thione derivatives from n-aryl-n-carboxyethyl-β-alanines

Depending on the substituents in the aryl moiety, the fusion of N-aryl-N-ethoxycarbonyl-β-alanines with thiocarbohydrazide gives di- or monotriazole derivatives, namely, 4-amino-(2-{[2-(4-amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)ethyl]anilino}ethyl)-4,5-dihydro-1H-1,2,4-triazole-5-thiones, 1-[2-(4-amino- 5-thioxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)ethyl]-2,3-dihydroquinolin-4(1H)-ones, 4-amino-3-[2-(4-methylanilino))ethyl]-4,5-dihydro-1H-1,2,4-triazole-5-thione and 4-amino-3-[2-(4-ethoxyanilino)-ethyl]-4,5-dihydro-1H-1,2,4-triazole-5-thione. A ditriazolethione derivative was also obtained from the diethyl ester of N-ethoxycarbonyl-N-(4-ethoxyphenyl)- β-alanine.     

An efficient and general enantioselective synthesis of some isoxazole-containing analogues of the neuroexcitant glutamic acid

Isoxazole amino acids are an important class of neuroexcitant which are difficult to prepare in enantiopure form. Diastereoselective alkylation of the enantiomerically pure glycine derivative, tert-butoxycarbonyl-2-(tert-butyl)-3-methyl-4-oxo-1-imidazolidinecarboxylate (Boc-BMI) with 4-bromomethyl-2-methoxymethyl-5-methylisoxazolin-5-one 5 or 5-bromomethyl-4-bromo-3-methoxyisoxazole, gives intermediates which under mild hydrolysis conditions produce the amino acids (S)- and (R)-bromohomoibotenic acid and (S)- and (R)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl) propionic acid with e.e. >99%.     

Synthesis of pyrido[1,2-a]pyrimido[4,5-d]pyrimidin-5-ones. Cyclization reaction of 4-[(3-hydroxy-2-pyridyl)amino]-2-phenyl-5-pyrimidinecarboxylic acid with acetic anhydride

Treatment of 4-[(3-hydroxy-2-pyridyl)amino]-2-phenyl-5-pyrimidinecarboxylic acid (X) with acetic anhydride under refluxing conditions afforded 10-hydroxy-2-phenyl-5H-pyrido[1,2-a]-pyrimido[4,5-d]pyrimidin-5-one acetate (IX). The intermediate X was prepared from 4-chloro-2-phenyl-5-pyrimidinecarboxylic acid ethyl ester (V). The reaction of V with the sodium salt of 2-amino-3-hydroxypyridine at room temperature gave 4-(2-amino-3-pyridyloxy)-2-phenyl-5-pyrimidinecarboxylic acid ethyl ester (VI). Treatment of VI with a hot aqueous sodium hydroxide solution and subsequent acidification gave X. Involvement of 4-[(3-hydroxy-2-pyridyl)amino]-2-phenyl-5-pyrimidinecaroboxylic acid ethyl ester (VIII) (Smiles rearrangement product) as an intermediate in the above alkaline hydrolysis reaction of VI to X was demonstrated by the isolation of VIII and its subsequent conversion into X under alkaline hydrolysis conditions. Acetylation of VIII with acetic anhydride in pyridine solution gave 4-[(3-hydroxy-2-pyridyl)amino]-2-phenyl-5-pyrimidinecarboxylic acid ethyl ester acetate (XI), which afforded IX on fusion at 220°. This alternative synthesis of IX from XI supported the structural assignment of IX. Fusion of VI gave 10-hydroxy-2-phenyl-5H-pyrido[1,2-a]pyrimido]4,5-d]pyrimidin-5-one (VII). The latter was also obtained when VIII was fused at 210°. Acetylation of VII with acetic anhydride afforded IX.     

Dual basic ionic liquid as a catalyst for synthesis of (2-amino-3-cyano-4H-chromen-4-yl) phosphonic acid diethyl ester and its molecular docking study

Research on Chemical Intermediates - A series of (2-amino-3-cyano-4H-chromen-4-yl) phosphonic acid diethyl ester derivatives were synthesized from salicylaldehyde, malononitrile and...     

Ibotenic acid analogues. Synthesis and biological testing of two bicyclic 3-isoxazolol amino acids

The bicyclic 3-isoxazolol amino acids (RS)-3-hydroxy-4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridine-4-carboxylic acid (5, 4-HPCA) and (RS)-3-hydroxy-4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridine-6-carboxylic acid (11, 6-HPCA) were synthesized as model compounds for studies of the structural requirements of central excitatory amino acid neurotransmitter receptors. 4-HPCA was synthesized via introduction of a methoxycarbonyl group into the 4-position of the lithiated N-nitroso intermediate 1. The key reaction in the synthesis of 6-HPCA is an intramolecular N-alkylation of the appropriately substituted acetamidomalonate derivative 7 using sodium hydride as a base. On the basis of the pKA values for 4-HPCA the existence of an intramolecular hydrogen bond in the zwitterionic form of this amino acid is proposed. 6-HPCA was shown by 1H NMR spectroscopy to adopt preferentially a conformation with the carboxylate group in an equatorial position. 4- and 6-HPCA were tested as agonists and antagonists at excitatory amino acid receptors on neurones in the cat spinal cord using microelectrophoretic techniques. Neither compound showed significant effects at these receptors.     

Synthesis and antimicrobial activity of some derivatives of (7-hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid hydrazide

(7-Hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid hydrazide (2) was prepared from (7-hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid ethyl ester (1) and 100% hydrazine hydrate. Compound 2, is the key intermediate for the synthesis of several series of new compounds such as Schiff's bases 3a-l, formic acid N'-[2-(7-hydroxy-2-oxo-2H- chromen-4-yl)acetyl] hydrazide (4), acetic acid N'-[2-(7-hydroxy-2-oxo-2H-chromen-4- yl)-acetyl] hydrazide (5), (7-hydroxy-2-oxo-2H-chromen-4-yl)-acetic acid N'-[2-(4- hydroxy-2-oxo-2H-chromen-3-yl)-2-oxoethyl] hydrazide (6), 4-phenyl-1-(7-hydroxy-2- oxo-2H-chromen- 4-acetyl) thiosemicarbazide (7), ethyl 3-{2-[2-(7-hydroxy-2-oxo-2H- chromen-4-yl)-acetyl]hydrazono}butanoate (8), (7-hydroxy-2-oxo-2H-chromen-4-yl)- acetic acid N'-[(4-trifluoromethylphenylimino)methyl] hydrazide (9) and (7-hydroxy-2- oxo-2H-chromen-4-yl)acetic acid N'-[(2,3,4-trifluorophenylimino)-methyl] hydrazide (10). Cyclo- condensation of compound 2 with pentane-2,4-dione gave 4-[2-(3,5- dimethyl-1H-pyrazol-1-yl)-2-oxoethyl]-7-hydroxy-2H-chromen-2-one (11), while with carbon disulfide it afforded 7-hydroxy-4-[(5-mercapto-1,3,4-oxadiazol-2-yl)methyl]-2H- chromen-2-one (12) and with potassium isothiocyanate it gave 7-hydroxy-4-[(5- mercapto-4H-1,2,4-triazol-3-yl)methyl]-2H-chromen-2-one (14). Compound 7 was cyclized to afford 2-(7-hydroxy-2-oxo-2H-chromen-4-yl)-N -(4-oxo-2-phenylimino- thiazolidin-3-yl) acetamide (15).     

5-Trifluoromethylfuryl derivatives of phosphocarboxylic acids

Methods of synthesis of trifluoromethylfuryl derivatives of phosphonocarboxylic acids are studied. By addition of diethyl hydrogen phosphite to alkyl 3-(5-trifluoromethylfur-2-yl)acrylate under the conditions of the Pudovik reaction the corresponding derivative of 3-phosphonopropionic acid was prepared. Diethyl (5-trifluoromethylfur-2-yl)methanephosphonate in presence of potassium tert-butylate reacts with ethyl acrylate to form trifluoromethylfuryl derivative of 4-phosphonobutyric or 4-phosphonopimelic acid depending on the reaction conditions. In the products of reaction of the alkyl 3-(5-trifluoromethylfur-2-yl)-3-(diethoxyphosphoryl) propionate with ethyl acrylate in the presence of potassium tert-butylate formation of trifluoromethylfuryl derivative of the 3-phosphonoadipic acid is detected. 3-(5-Trifluoromethylfur-2-yl)-3-(diethoxyphosphoryl) propionic acid and its acid chloride are synthesized. The latter compound is used for acylation of glycine to form the corresponding N-acyl derivative. It is suggested that such compounds may be transported in the cell using usual channels of transportation of the amino acids and short peptides.     

Enantioselective synthesis of both enantiomers of the neuroexcitant 2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl) propanoic acid (ATPA)

The preparation of both enantiomers of 2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl) propanoic acid (ATPA), 1, an analogue of the neuroexcitant 2-amino-3-(3-hydroxy-5-methyl-4-yl) propanoic acid (AMPA) is described. The enantiomerically pure glycine derivative tert-butoxycarbonyl-2-(tert-butyl)-3-methyl-4-oxo-1-imidazolidinecarboxylate (BOC-BMI) was coupled with 4-bromomethyl-2-methoxymethyl-5-tert-butylisoxazolin-3-one 6 to give the intermediates (2R,5R)-8 and (2S,5S)-8. These alkylated products were hydrolyzed under mild conditions to give enantiopure (R)-1 and (S)-1 with e.e.'s in excess of 99% in 33% overall yield.     

Thiazolecarboxylic Acid Derivatives. 1. N-Substituted 2-Amino-4-methylthiazole-5-carboxylic Acid Derivatives

Acylation of the ethyl ester and anilide of 2-amino-4-methylthiazole-5-carboxylic acid gave 2-acetyl(arylsulfonyl)amino derivatives. Methylation of acetylaminothiazole and subsequent deacetylation gave 2-methylamino-4-methylthiazole-5-carboxylic acid, which was then converted into esters. The ethyl ester and anilide of thiazole-2-carboxylic acid were used as starting compounds for the synthesis of 2-dimethylaminoformimino- and 2-chlorobenzenesulfonylureido derivatives.     

Nitrogen and sulfur containing heterocycles. 50. Synthesis and reactions of 6-oxopyrimido[4,5-b][1,4]thiazine-7-carboxylic acid derivatives

Reaction of 5-amino-6 mercaptopyrimidines with diethyl bromomalonate gave ethyl 6-oxopyrimido-[4,5-b][1,4]thiazine-7-carboxylates, from which there was synthesized a series of derivatives at the carboxyl group (amides, hydrazides, and, from the latter, urethanes). Desulfurization of the 6-oxopyrimidothiazine-7-carboxylic acid esters gave N-(pyrimidin-5-yl)monoamides of ethyl malonate.For communication 49 see [1].Center for Chemistry of Drugs—All-Russian Research Chemical-Pharmaceutical Institute, Moscow 119021, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 822–828, June, 1999.     

Synthesis of 1,3,4-thiadiazol-2-ylacetic acid derivatives

1,3,4-Thiadiazol-2-ylacetic acids 4 were prepared by lithiation of 2-methyl-1,3,4-thiadiazoles 1 , followed by treatment with carbon dioxide. Diethyl 1,3,4-thiadiazol-2-ylmalonates 6 were prepared by nucleophilic displacement reaction of the corresponding bromides 5 with diethyl malonate. Introduction of the amino group at the a-position of 4 or 6 was carried out via oximation or bromination to give the amino ester 9 or 4 . Attempts to prepare DL-α-amino-1,3,4-thiadiazol-2-ylacetic acids from 9 or 4 were unsuccessful because the amino acids were decarboxylated too rapidly to be isolated in the free form.     

The synthesis of a pyrido[3,4-d]pyrimidine analog of pteroic acid

A multistep synthesis of ethyl 5-amino-2-methyIpyridine-4-carboxylate (5a) starting from ethyl acetopyruvate and nitroacetamide is described. The condensation of 5a with benzoylcyanamide gave 2-amino-3-benzoyl-6-methylpyrido[3,4-d]pyrimidin-4(3H) one (10), which could be hydrolyzed in alkali to give 2-amino-4-hydroxy-6-methylpyrido[3,4-d]pyrimidine (9). Free radical bromination of 10 in bromotrichloromethane gave a mixture of the bromo- and chloromethyl- derivatives (11). Fusion of 11 with ethyl p-aminobenzoate, followed by alkaline hydrolysis gave the corresponding pteroic acid analog (12).     

Synthesis of isonipecotinoyl analogues of aminopterin and folic acid

The preparation of isonipecotinoyl analogues of aminopterin and methotrexate is described. Condensation of diethyl N-isonipecotinoyl-L-glutamate 4 with 2-amino-5-bromomethyl-3-cyanopyrazine 5 afforded diethyl N-(N-[(2-amino-3-cyanopyrazin-5-yl)methyl]isonipecotinoyl)-L-glutamate 6 . Cyclisation of 6 with guanidine followed by blocking group hydrolysis afforded N-([N-(2,4-diaminopteridin-6-yl)methyl]isonipecotinoyl)-L-glutamic acid 8 . Coupling of N-(2-amino-4(3H)ioxopteridin-6-yl]methyl)isonipecotinic acid 11 with diethyl L-glutamate gave diethyl N-[(N-[2-amino-4(3H)-oxopteridin-6-yl]methyl)isonipecotinoyl]-L-glutamate 12 . Blocking group hydrolysis afforded N-[(N-[2-amino-4(3H)-oxopteridin-6-yl]methyl)isonipecotinoyl]-L-glutamic acid 13 .     

Thiadiazole ring opening in the derivatives of 2-substituted 5-(1,2,3-thiadiazol-4-yl)-3-furoic acid under the action of bases

Transformations of the derivatives of 2-substituted 5-(1,2,3-thiadiazol-4-yl)-3-furoic acid under the action of bases has been studied. In the presence of potassium tert-butylate in THF, the studied compounds decompose with the cleavage of the thiadiazole ring, liberation of nitrogen, and formation of labile acetylene thiolates. In the presence of methyl iodide, these salts form stable 2-methylthioethynylfurans. Under the action of sodium ethylate in ethanol, thiadiazole ring of ethyl [2-methyl-5-(1,2,3-thiadiazol-4-yl)]-3-furoate is split to form the corresponding sodium acetylene thiolate. Under the action of ethanol, two molecules of this salt give bis(furyl)dithiafulvene. In the DMF–potassium carbonate system, acetylene thiolates react with primary and secondary amines giving thioamides of (4-ethoxycarbonyl-5-methylfur-2-yl)acetic acid. Treating of ethyl 2-methyland 2-N-morpholinomethyl-5-(1,2,3-thiadiazol-4-yl)-3-furoates with hydrazine hydrate leads to hydrazinolysis of the ester group and cleavage of thiadiazole ring resulting in the formation of hydrazides of 4-hydrazinocarbonylfur-2-ylacetic acid. In the case of ethyl 2-acetoxymethyl- and 2-(4-nitrophenoxy)methyl-5-(1,2,3-thiadiazol-4-yl)-3-furoates, thiadiazole ring is retained and exclusively hydrazinolysis of the ester groups is observed.     

Synthesis of copoly(vinylamine-vinylalcohol) containing two kinds of asymmetric nucleic acid base derivatives as grafted pendants

Preparation of new model polymers of polynucleotides with poly(vinylamine-vinylalcohol) [P(Vam-Val)] backbones and different kinds of nucleic acid base derivatives as grafted pendants is described. At first, the grafting of (?) and (±)-2-(thymin-1-yl)propionic acid [(?) and (±)TPA] onto linear P(Vam-Val) at the amino group via an amide bond was carried out in a mixed solvent of ethanol-dimethylformamide by selective N-acylation of the active ester of N-hydroxy-5-norbornene-2,3-dicarboximide (HONB) or N-hydroxysuccinimide (HOSu). This procedure gave the corresponding hydroxyl polymers P[Vam(?)T-Val] and P[Vam(±)T-Val]. In addition, direct, low temperature esterification was used to graft (?), (±)TPA, and (±)-2-(uracil-1-yl)propionic acid, [(±)UPA], onto the hydroxyl polymer at the hydroxyl group via an ester bond. This process gave the corresponding copoly(Vam-Val) with different or the same kinds of nucleic acid base derivatives. P[Vam(?)-Ve(?)T], P[Vam(±)T-Ve(±)T], P[Vam(?)T-Ve(±)U], and P[Vam(±)T-Ve(±)U] are representative examples. The related monomer and segmental model compounds were also prepared by this method; 3-aminopentane, 3-pentanol, 3-amino-1-propanol, and threo-2-amino-4-pentanol were employed in the syntheses. The segment models were separated and purified using HPLC techniques.     

Derivatives of 2,3-Dihydrocyclopenta[d] pyrido[1,2-a] pyrimidin-10(1H)one

The annulation of 2-amino-3-hydroxy-, 2-amino-3-carboxy-, and 2-amino-3-methylpyridine with ethyl cyelopenlanone-2-earboxylate led to the 5-hydroxy-, 2 , 5-carboxy-, 3, and 5-methyl-, 4 , derivatives of the 2,3-dihydrocycloperita[d]pyrido[1,2-a]pyrimidin-10(1H) one heterocycle. Alkylation of 2 with α-bromotolue, ne gave the 5-benzyloxy derivative.     

Boron chelate complexes with 4-[N-(R-pyrid-2-yl)carbamoyl]-3-amino-2-cyanobuten-2-ic acid esters (codimers of N-(R-pyrid-2-yl)amides and the ethyl ester of cyanoacetic acid)

Mono- and binuclear boron chelates have been synthesized by the action of butylthiodibutylborane on the ethyl esters of 4-[N-(R-pyrid-2-yl)carbamoyl]-3-amino-2-cyanobuten-2-ic acids (codimers of N-(R-pyrid-2-yl) amides and the ethyl ester of cyanoacetic acid). Complexes of this type can exist in solution in the form of two tautomers: acetamide acid derivatives or the corresponding ketene N,O-acetals.N. D. Zelinski Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2162–2170, September, 1992.