Studies on pyrazines. 17.. An efficient synthesis of pteridine-6-carboxylic acids

2,4-Diaminopteridine-6-carboxylic acid ( 1 ) and pterin-6-carboxylic acid ( 2 ) were prepared by permanganate oxidation of the corresponding 6-(2-furyl)-substituted pteridines under much milder conditions. Several attempts to cleave the furan ring with other oxidizing agents are also described.     

Studies on pyrazines. 13 . Chlorination of 1-hydroxy-2(1H)-pyrazinones with phosphoryl chloride. Formation of 2,5-dichloro-3-phenylpyrazine from 1-hydroxy-3-phenyl-2(1H)-pyrazinone

The chlorination of 1-hydroxy-3-phenyl-2(1H)-pyrazinone with phosphoryl chloride proceeded to 5-chloro-3-phenyl-2(H)-pyrazinone or 2,5-dichloro-3-phenylpyrazine on heating to elevated temperatures. To define the mechanism of the novel formation, reactions of the parent or methyl-substituted 1-hydroxy-2(1H)-pyraz-inones with the same reagent were investigated.     

A mass spectrometric study of 4-hydroxy-6-methyl-2-pyridone and its derivatives

The mass spectra of 4-hydroxy-6-methyl-2-pyridone, its N-methyl and N-phenyl derivatives, and also their 4-O-acetyl and 3-C-acyl derivatives have been studied. The proposed fragmentation pathways were supported by comparison of the mass spectra and in some cases by the spectra of deutero analogues. A strong N-phenyl group effect has been found, which in the case of N-phenyl-4-hydroxy- and N-phenyl-4-acetoxy-6-methyl-2-pyridones promotes the formation of the stable [M—H]+ and [M—CH₃CO]+ ions respectively. These ions are not characteristic of the N—H and N—Me analogues.     

Studies on pyrazines. 7. The synthesis of 5-chloropyrazinecarboxylic acid

The titled carboxylic acid ( 1 ) was prepared by condensation of 2-furylglyoxal with aminoacetamide followed by chlorination of the resulting 2-hydroxy-5-(2′-furyl)pyrazine ( 2 ) and permanganate oxidation. The acid was further converted into methyl ester and 5-hydroxypyrazinecarboxylic acid.     

Studies on pyrazines. 14 The syntheses of 2,5-dihydroxypyrazines and their derivatives

Reaction of phenylglycinamide ( 1c ) with ethyl benzoylformate ( 2c ) in the presence of refluxing ethanolic sodium ethoxide gave 2,5-dihydroxy-3,6-diphenylpyrazine ( 3i ) in 19% yield. This synthetic method, however, was limited to the preparation of 3i . On the other hand, α-aminoamides 1 condensed with α-ketoesters 2 to give the intermediates 5 , which were also prepared by condensation of 1 with α-ketalesters 6 , followed by hydrolysis of the ketal moeity. Cyclization of 5 with refluxing methanolic sodium methoxide gave only disubstituted 2,5-dihydroxypyrazines 3 . Acetylation of 5 with refluxing acetic anhydride/acetic acid led to direct formation of 2,5-diacetoxypyrazines 9 . Similarly, compounds 5 could be converted into 2,5-dichloropyrazines 4 .     

The synthesis of 3-deazaorotidine and related nucleoside derivatives of 4-hydroxy-2-pyridone

Condensation of 6-earbethoxy-4-hydroxy-2-pyridone or a silyl derivative of 5-earbomethoxy-4-hydroxy-2-pyridone with 2′,3′,5′-tri-O-benzoyl-D-ribofuranosyl halide has provided the 3-deaza analogs of orotidine and uridine-5-carboxylic acid. The corresponding amides have also been prepared in view of their possible structural relationship to l-β-D-ribohiranosyl nicotinamide. Tri-O-benzoyl-3-deazauridine was treated with N-bromosuccinimide to give, after deblocking, 3-bromo-4-hydroxy-1-(β-D-ribofuranosyl)-2-pyridone. The anomeric configuration of these nuclcosides was confirmed by pmr spectroscopy.     

Brominated derivatives of 4-hydroxy- and 4-methoxy-6-methyl-2H-pyran-2-ones

Twenty-five different brominated derivatives of 4-hydroxy-6-methyl-2-pyrone (triacetic acid lactone) and 3-acetyl-4-hydroxy-6-methyl-2-pyrone (dehydroacetic acid) have been prepared. Fifteen derivatives have not been previously described and the preparations of a few known products have been improved. Bromination at C-3, C-5, methyl group at C-6 and deacetylations at C-3 have been the types of reactions used.     

First synthesis of 4-oxo-6-trifluoromethyl-4H-thiopyran-2-carboxylic acid and its derivatives

Treatment of 6-trifluoromethylcomanic acid with sodium hydrosulfide afforded for the first time 4-oxo-6-trifluoromethyl-4H-thiopyran-2-carboxylic acid (6-trifluoromethylthiocomanic acid). When heated or treated with H₂SO₄, this acid easily underwent decarboxylation leading to 2-trifluoromethyl-4H-thiopyran-4-one. Because of this, both ethyl and methyl 6-tri-fluoromethylthiocomanates were obtained in low yields (15–23%). Decarboxylation of 6-tri-(di)fluoromethylcomanic acids gave 2-tri(di)fluoromethyl-4H-pyran-4-ones in 77–80% yields.     

Heteroadamantanes and their derivatives. 3. The synthesis of 6-hydroxy-5-methoxycarbonyl-1,3-diazaadamantane

The interaction of methyl 3-oxo-4-(phenylthio)butyrate with formaldehyde and ammonium acetate yielded 5-methoxycarbonyl-6-oxo-7-phenylthio-1,3-diazaadamantane, which, on being heated with skeletal nickel in isopropanol was converted into 6-hydroxy-5-methoxycarbonyl-1,3-diazaadamantane. The structures of the compounds have been confirmed by IR and PMR spectroscopy.For Communication 2, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 661–663, May, 1985.     

Synthesis of 2-carbethoxy-3-methyl-4-hydroxy-6-phenylbenzofuran derivatives

4-Hydroxybenzofuran derivatives were synthesized, and their reactions with bromine and nitric acid were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 879–882, July, 1976.     

Studies on pyrazines. 18. A new and convenient synthesis of 2-amino-3-cyanopyrazine

The titled compound, 2-amino-3-cyanopyrazine ( 1 ), was prepared by reaction of 3-aminopyrazine 1-oxide ( 7 ) with trimethylsilyl cyanide. Furthermore, conditions of individual steps in synthetic route to 7 starting from 2-pyrazinecarboxamide were optimized.     

Studies on pyrazines. 15. A convenient synthesis of 2,5-dihydroxypyrazines

The reaction of 2,5-dimethoxypyrazines with iodotrimethylsilane followed by hydrolysis was investigated to prepare the title compounds.     

The synthesis of 5- and 6-hydroxy-2-methylisoquinuclidine

The reduction of the isomeric 5,6-epoxy-2-carboethoxyisoquinuclidines with lithium aluminum hydride afforded 5- and 6-hydroxy-2-methylisoquinuclidine. Contrary to expectation essentially single epimers were obtained for each alcohol.     

Studies on pyrazines. 35. An improved synthesis of bromopyrazines from hydroxypyrazines

The synthesis of bromopyrazines from hydroxypyrazines was successfully effected by the procedure via trimethylsilyloxypyrazines, the sequence of which proceeds under mild conditions and does not require the isolation of intermediate.     

4-Hydroxy-2-quinolones. 152*. 3-acetyl-4-hydroxy-2-oxo-1,2-dihydroquinoline and its biologically active derivatives

A synthesis and study of the spatial structure of 3-acetyl-4-hydroxy-2-oxo-1,2-dihydroquinoline have been carried. 1-R-4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carboxylic acids [1-(4-hydroxy-2-oxo-1,2-dihydroquinolin-3-yl)ethylidene]hydrazides were prepared from this compound by two routes. A comparative analysis of the antitubercular properties of the synthesized compounds and of the closely structurally related N,N′-di(1-R-4-hydroxy-2-oxo-1,2-dihydroquinoline-3-carbonyl)hydrazines has been performed. *For Communication 151 see [1]. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 214–222, February, 2009.     

Studies on the syntheses of heterocyclic compounds. Part DCLV.. Two stereoisomers of 1-benzyl-5-hydroxy-6-(4-methoxybenzyl)-4,5-dimethylpiperidin-2-one

The stereochemistry of two diastereoisomers of 1-benzyl-5-hydroxy-6-(4-methoxybenzyl)-4,5-dimethylpiperidin-2-one (IV), which is an intermediate for synthesis of pentazocine (I), was elucidated.     

The first total synthesis of the 6-hydroxy-4E-sphingenines

Ceramides containing the 6-hydroxy-4E-sphingenines, previously unknown long-chain bases, have recently been found in human skin. A total synthesis of 6-hydroxy-4E-sphingenines has been achieved.     

Studies on the reaction of 3-substituted-4-hydroxy-2H-1,2-benzothiazine 1,1-dioxides with aryl isocyanates and the synthesis of corresponding derivatives

The reaction of 3-substituted-4-hydroxy-2H-1,2-benzothiazine 1,1-dioxides with aryl isocyanate under different equivalents of strong base NaH was studied.Seventeen of new derivatives were obtained whose structures were characterized by 1H NMR,IR,MS,elementary analysis and FeCl3 test.