Über Pterinchemie. 77. Mitteilung)Das (6R,S)-5-Formyl-6-methyl-5,6,7,8-tetrahydropterin: Synthese,chemische und physikalisch-chemische Eigenschaften

(6R,S)-5-Formyl-6-methyl-5,6,7,8-tetrahydropterine: Synthesis, Chemical and Physico-chemical Properties (6R, S)-5-Formyl-6-methyl-5,6,7,8-tetrahydropterine ( III ), a model substance for the biologically important 6-substituted 5-formyl-5,6,7,8-tetrahydropterines, was obtained for the first time by formylation of the corresponding tetrahydropterine with formic acid. Compound III , analogously to the other known 5-acyltetrahydropterines, exists in solution (except in DMSO) as a mixture of two rotamers IIIa and IIIb . The two H-C(7) in III have the same chemical shift and the same coupling constant to H-C(6), giving rise to a A,A',X,C-system. Conformational analysis of III , based on its ¹H-NMR,-spectrum, shows that the methyl group is pseudo-axial and the formyl group pseudo-equatorial. Moreover, the H(X)-C(6) bond lies nearly in the plane bisecting the C(6)-C(7)-H(A), C(6)-C(7)-H(A') dihedral angle; the C(6) and C(7) lie outside the N(5)-C(4a)-C(8a) plane and the tetrahydropyrazine cycle must be extremely strained, according to Dreiding models.     

Über Pterinchemie. 61. Mitteilung. Die Kristallstruktur von 5-Formyl-6,7-dimethyl-5,6,7,8-tetrahydropterin

The crystal structure of 5-formyl-6,7-dimethyl-5,6,7,8-tetrahydropterine The crystal structure of the title compound, a tetrahydropterine, has been determined by X-ray analysis (direct method) and refined with 1579 structure amplitudes to R = 0.054. The crystal system is triclinic, space group P1 , with unit cell dimensions a = 7.171, b = 7.255, c = 12.369 Å, α = 100.64, β = 93.32, γ = 98.27°. The tetrahydropyrazine ring exists in a distinctly flattened conformation. The C(13)- and C(14)-CH₃-groups possess a cis-configuration with axial position for C(13)-CH₃ and equatorial for C(14)-CH₃. The carbonyl-group of the N-formyl function has an (E)-configuration.     

Über Pterinchemie. 58. Mitteilung [1]. Sterische Eigenschaften von acylierten 5,6,7,8-Tetrahydropterinen. Rotameren von 5-Trifluoracetyl-tetrahydropterin-Derivaten

Sterochemical Properties of the Acylated 5,6,7,8-Tetrahydropterines. Rotameres of the 5-Trifluoroacetyl-tetrahydropterine Derivatives 6-Methyl- and 6,7-dimethyl-5,6,7,8-tetrahydropterine are acylated with the anhydrides of acetic acid and trifluoroacetic acid. It is shown that the reactivity of the nitrogen otoms increases in the following order: N(3), N(8), N(2′) and N(5). Two rotameres are present in the ¹H-NMR. spectra of the N(5)-trifluoroacetates, but not in those of the N(5)-acetates.     

Electrochemistry of 6-methyl-5,6,7,8-tetrahydropterin

The electrochemical oxidation of 6-methyl-5,6,7,8-tetrahydropterin (6-MTHP), the most effective of the synthetic aromatic amino acid hydroxylase pseudo cofactors, has been studied in aqueous solution over a wide pH range at a pyrolytic graphite electrode. The first electrooxidation of 6-WTHP occurs by a quasi-reversible 2e-2H⁺ reaction giving an unstable quinonoid-dihydropterin. The latter undergoes a first order chemical follow-up reaction yielding 6-methyl-7,8-dihydropterin (6-MDHP). At pH values ?5.6 6-MDHP forms an equilibrium mixture of a covalently hydrated species and non-hydrated species. The covalently hydrated form of 6-MDHP is electrooxidized in a 2e-2H⁺ quasi-reversible reaction to another unstable quinonoid that appears to undergo a two-step rearrangement to 6-methylpterin. Non-hydrated 6-MDHP is electrooxidized at the most positive potential in an irreversible 2e-2H⁺ reaction giving 6-methylpterin.     

Über Pterinchemie. 57. Mitteilung. Zur Konfiguration und Konformation von 6,7-Dimethyl-und 5,6,7-Trimethyl-5,6,7,8-tetrahydropterin

Configuration and conformation of 6,7-Dimethyl- and 5,6,7-Trimethyl-5,6,7,8-tetrahydropterines. During the hydrogenation of 6,7-dimethylpterine, cis-6,7-dimethyl-tetrahydropterine is formed. A possible conformation for this substance and for the 5,6,7-trimethyl derivative, which is obtained from it, is discussed, taking the ¹H-NMR. spectra of both tetrahydropterines into consideration.     

Über Pterinchemie 23. Mitteilung [1]. Radikalbildung während der Oxydation von Tetrahydrofolsäure und 5,6,7,8-Tetrahydropterin

EPR. investigations show the existence of one-electron oxidation of 5,6,7,8-tetrahydropterine and tetrahydrofolic acid resulting in unstable cationic radicals of red color which are trapped at liquid nitrogen temperature.     

Über Pterinchemie. 69 Mitteilung [1]. Konformationsanalyse von 5,6,7,8-Tetrahydropteroinsäure und 5,6,7,8-Tetrahydro-L-folsäure

Conformational analysis of 5,6,7,8-tetrahydropteroic acid and 5,6,7,8-tetrahydro-L -folic acid In the 360-MHz-¹H-NMR.-spectrum of (6R, S)-9,9-dideuterio-5, 6, 7, 8-tetrahydropteroic acid (racemic) (XIII) (AMX-System, Fig. 4) and (6R, S)-9,9-dideuterio-5, 6, 7, 8-tetrahydro-L -folic acid (diastereomeric) (XVI) the H_a–C(6) and H_a–C(7) show a vicinal coupling constant of 6,7 Hz and the H_a–C(6) and H_e–C(7) one of 3,2 Hz. The first coupling constant provides evidence for an approximate trans-diaxal arrangement of H_a–C(6) and H_a–C(7), and the second for a gauche conformation of H_a–C(6) and H_e–C(7). The tetrahydropyrazine ring in the racemic 5, 6, 7, 8-tetrahydropteroic acid (III) and in the diastereomeric 5, 6, 7, 8-tetrahydro-L -folic acid (XVII) exists therefore in a half-chair conformation with a pseudoequatorial position of the side chain at C(6) (Fig.5).     

Über Pterinchemie 51. Mitteilung [1] CNDO-Rechnungen an Pterin, 6,7-Dimethyl-7,8-dihydropterin und 5-Formyl-6, 7-dimethyl-5,6,7,8-tetrahydropterin

The ¹³C-NMR.-spectra of 7,8-dihydropterines and 5,6,7,8-tetrahydropterines show a large difference in the chemical shifts of the 4a- and 8a-sp²-carbon atoms. From the CNDO calculations it is apparent that there is a considerable difference in electron density at C(4a) and C(8a) atoms, which leads to a strong polarity of the C? C-Bond. The electron distribution in the highest occupied molecular orbital (HOMO) is discussed.     

Über Pterinchemie. 59. Mitteilung [1]. Konformationsanalyse von acylierten 5,6,7,8-Tetrahydropterinen

Conformational Analysis of Acylated 5,6,7,8-Tetrahydropterines The conformation of N(5)-acetates, and of N(5)- and N(8)-trifluoroacetates, respectively, of 6-methyl- and cis-6, 7-dimethyl-tetrahydropterines is studied by ¹H-NMR. spectroscopy. It is shown that the methyl group next to the acylated nitrogen atom is in quasi-axial position.     

Reaction of 5,6,7,8-Tetrahydropterin with Iron(III) Acetylacetonate. Detection of Radical Cations by Electrospray Ionization Mass Spectrometry

The experimental conditions developed for the detection of rather stable radical cations in solution by electrospray-ionization mass spectrometry (ESI-MS) of a Fe^II complex of 2-amino-5,6,7,8-tetrahydro-5-methylpteridin-4 (3H)-one ( 1c ) are used to observe the formation of the more unstable radical cations formed from 2-amino-5,6,7,8-tetrahydropteridin-4(3H)-one ( 1a ) and tris(pentane-2,4-dionato)iron(III) ([Fe^III(acac)₃]; 4 ) and to monitor their oxidation to the corresponding p-quinonoid dihydropterin complexes. These results contribute to the understanding of the important role played by 6β-5,6,7,8-tetrahydro-L -biopterin ( 1b ; a homologue of 1a ) together with iron as constituent of some cofactors. The complexes obtained from 1a and iron may be considered, e.g. as a model of the cofactor of the phenylalanine hydroxylase. Moreover, we describe an improved synthesis of 1c .     

Reactions of 2-ethoxycarbonyl(carboxy)-5,6,7,8-tetrafluorochromones with N-nucleophiles

The direction of reactions of 2-ethoxycarbonyl-5,6,7,8-tetrafluoro- and 2-carboxy-5,6,7,8-tetrafluorochromones with ammonia, methylamine, hexylamine, and aniline depends on the inductive effect of the substituent at position C-2 of the chromone and on the basicity of the amine. Nucleophilic aromatic substitution of a fluorine atom takes place in the interaction of 2-ethoxycarbonyl-5,6,7,8-tetrafluorochromone with secondary amines (morpholine,N-methylpiperazine) and ethylenediamine.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 904–907, May, 1994.     

Proton and carbon-13 nuclear magnetic resonance spectroscopy and conformational aspects of 5,6,7,8-tetrahydro-4-chromanone derivatives

The 25 MHz ¹³C and 350 MHz ¹H-nmr spectra of the title compounds are reported. Conformational equilibria in variously substituted 5,6,7,8-tetrahydrochromanones are discussed. Compounds bearing a t-butyl group at the 6 position appear to be conformationally homogenous.     

Reactions of 5,6,7,8-tetrafluoro-4-hydroxycoumarin derivatives with benzylamine and aniline

5,6,7,8-Tetrafluoro-4-hydroxycoumarin reacted with benzylamine under mild conditions to give a stable salt, while its refluxing with aniline or benzylamine in xylene afforded 5,6,7,8-tetrafluoro-4-phenyl(benzyl)aminocoumarins. Reactions of 3-acetyl(acetimidoyl)-5,6,7,8-tetrafluoro-4-hydroxycoumarins with benzylamine followed different pathways, depending on the solvent. Condensation at the acyl substituent can be accompanied by replacement of the F atom in position 7. 3-Acetylcoumarin formed a salt, while 3-acetimidoylcoumarin yielded a 7-monosubstituted product. 3-Acetyl(acetimidoyl)-5,6,7,8-tetrafluoro-4-hydroxycoumarins reacted with aniline to give only 5,6,7,8-tetrafluoro-4-hydroxy-3-(N-phenylacetimidoyl)coumarin. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1170–1174, July, 2006.     

Notizen zur Synthese sulfonierter Derivate von 5,6,7,8-Tetrahydro-1-naphthylamin und 5,6,7,8-Tetrahydro-2-naphthylamin

Notes on the Synthesis of Sulfonated Derivatives of 5,6,7,8-Tetrahydro-1-naphthylamine and 5,6,7,8-Tetrahydro-2-naphthylamine Sulfonation of 5,6,7,8-tetrahydro-1-naphthylamine ( 1 ) with sulfuric acid gave a mixture of 1-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 2 ), 4-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 13 ) and 4-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid ( 3 ). The same reaction with 5,6,7,8-tetrahydro-2-naphthylamine ( 20 ) yielded 3-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 21 ); formation of 2-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid ( 16 ) or of 3-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid ( 24 ) was not observed. Treatment of 4-bromo-5,6,7,8-tetrahydro-1-naphthylamine ( 4 ) or of its 4-chloro analogue 5 with amidosulfuric acid gave 1-amino-4-bromo-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 9 ) and its 4-chloro analogue 10 , respectively, which were dehalogenated to 2 . Preparations of 13 and 24 were achieved by sulfonation of 5-nitro-1,2,3,4-tetrahydronaphthalene ( 14 ) and 6-nitro-1,2,3,4-tetrahydronaphthalene ( 22 ) to 4-nitro-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 15 ) and 3-nitro-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid ( 23 ), respectively, followed by Béchamp reductions. The sulfonic acid 13 was also obtained by hydrogenolysis of 4-amino-1-bromo-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 11 ) or of its 1-chloro analogue 12 ; compounds 11 and 12 were synthesized from N-(4-bromo-5,6,7,8-tetrahydro-1-naphthyl)acetamide ( 7 ) and from its 4-chloro analogue 8 , respectively, by sulfonation with oleum and subsequent hydrolysis. By ‘baking’ the hydrogensulfate salt of 1 or 20 compounds 3 and 21 were obtained, respectively. Synthesis of 16 was achieved by sulfur dioxide treatment of the diazonium chloride derived from 2-nitro-5,6,7,8-tetrahydro-1-naphthylamine ( 17 ) giving 2-nitro-5,6,7,8-tetrahydronaphthalene-1-sulfonyl chloride ( 18 ), followed by hydrolysis of 18 to the corresponding sulfonic acid 19 and final reduction.     

Iron and molybdenum carbonyls of 5,6,7,8-tetramethylenebicyclo[2.2.2]-oct-2-ene

The reaction of the title ligand with iron carbonyls under various conditions gives (tetrahapto)5,6,7,8-tetramethylenebicyclo[2.2.2]oct-2-ene-exotricarbonyliron (I) and the bis(tetrahapto)endoexo-(II) and diexohexacarbonyl diiron (III) complexes as main products. The monoexo complex reacts with Mo(CO)₃(CH₃CN)₃ giving a (tetrahapto)iron(hexahapto)molybdenum complex (IV).     

Über Pterinchemie. 85. Mitteilung. Polyacetylierte 5,6,7,8-Tetrahydro-D- und -L-neopterine. Ein besonderer Fall von N(5)-Alkylierung des 5,6,7,8-Tetrahydroneopterin-Gerüstes

Polyacetylated 5,6,7,8-Tetrahydro-D - and L -neopterins. A Special Case of N(5)-Alkylation of 5,6,7,8-Tetrahydroneopterins Improved conditions are reported for the preparation of the earlier described (6R)- and (6S)-1′-O,2′-O,3′-O,2-N,5-pentaacetyl-5,6,7,8-tetrahydro-L -neopterins, one of which could be obtained as pure crystals. Its structure, determined by X-ray-diffraction analysis, corresponds to the (6R)-enantiomer. The method has also been used to make the corresponding D -diastereoisomers. Further acetylation of (6RS)-1′-O,2′-O,3′-O,2-N-tetraacetyl-5,6,7,8-tetrahydro-D -neopterin under drastic conditions yields a mixture of several polyacetylated D -neopterin derivatives and a polyacetylated ethyl-tetrahydro-D -neopterin which was isolated in crystalline form and established by X-ray-diffraction analysis to be (6R)-1′-O,2′-O,3′-O,4-O,2-N,2-N,8-heptaacetyl-5-ethyl-5,6,7,8-tetrahydro-D -neopterin.     

1-Azabicyclic compounds. 24. Selectivity of position of nitration of 1,2-dihydropyrrolizine, 5,6,7,8-tetrahydropyrrocoline and pyrrole homologs

The selectivity of the position of nitration of 1-methylpyrrole, 1,2-dimethylpyrrole, 1,2-dihydropyrrolizine, and 5,6,7,8-tetrahydropyrrocoline was found. In contrast to the selectivity of substitution during nitration of their carbocyclic analogs, o-xylene, indane and tetraline, the fraction of the -nitro-isomer in the nitration products of 1,2-dimethylpyrrole is smaller than the fraction of -nitro derivatives of 1,2-dihydropyrrolizine and 5,6,7,8-tetrahydropyrrocoline, and in the two latter cases the isomers are almost equally distributed. During nitration of the above bicyclic pyrroles, the Mills-Nixon effect does not appreciably influence the selectivity of the position of the reaction.See [1] for Communication 23.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1489–1491, November, 1987.     

Azole. 44.

The structure analyses of racemic 3‐chloro‐1‐(4‐morpholino‐5‐nitro­imidazol‐1‐yl)­propan‐2‐ol, C₁₀H₁₅ClN₄O₄, (II), and 3‐chloro‐1‐(5‐morpholino‐4‐nitro­imidazol‐1‐yl)­propan‐2‐ol, C₁₀H₁₅ClN₄O₄, (III), have been undertaken in order to determine the position of the morpholine residue in these two isomers. The morpholine residue in (II) is connected at the 4‐position, while in (III), it is connected at the 5‐position of the imidazole ring. The morpholine mean planes and nitro groups in the two compounds deviate from the imidazole planes to different extents. The nitro groups in (II) and (III) take part in the conjugation system of the imidazole rings. In consequence, the exocyclic C—N bonds are significantly shorter than the normal single Csp²—NO₂ bond and the nitro groups in (II) and (III) show an extraordinary stability on treatment with morpholine and piperidine [Gzella, Wrzeciono & Pöppel (1999). Acta Cryst. C 55 , 1562–1565]. In the crystal lattice, the mol­ecules of both compounds are linked by O—H?N and C—H?O intermolecular hydrogen bonds.     

Synthesis of 3-aryl-5,6,7,8-tetrahydro-2-benzopyrilium salts and corresponding isoquinolines

,-Unsaturated ketones (such as cyclohexylideneacetophenone) are formylated with dichloromethyl butyl ether in the presence of anhydrous aluminum chloride. A method has been developed for the synthesis of 3-aryl-substituted 5,6,7,8-tetrahydro-2-benzopyrilium salts unsubstituted in 1 position. The thus-synthesized salts are converted into the corresponding 5,6,7,8-tetrahydroisoquinolines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 5, pp. 585–587, May, 1970.     

Derivatives of 4-hydroxy-5,6,7,8-tetrafluorocoumarin in reactions with o-aminothiophenol

The derivatives of 4-hydroxy-5,6,7,8-tetrafluorocoumarin in reactions witho-aminothiophenol yield products of S-substitution at C⁷ atom, 7-substituted 5,6,8-trifluorocoumarins afford benzothiazoles as a result of cleavage of the pyrone cycle, 2-methyl-3-ethoxycarbonyl-5,6,7,8-tetrafluorochromone undergoes acidic cleavage to 2-(2-hydroxy-3,4,5,6-tetrafluorophenyl)benzothiazole. S-Substituted coumarins in alkaline media suffer decomposition to acetophenone. In acidic media 3-iminoacetyl-4-hydroxy-5,6,8-trifluoro-7-(2-aminophenylthio)coumarin affords 2-methyl-5,6,8-trifluoro-7-(2-aminophenylthio)chromone. In condensation of 4-hydroxy-5,6,8-trifluoro-7-(2-aminophenylthio)coumarin in the presence of NaH was isolated 4-hydroxy-5,6-difluoro-2H-pyrano[6,5-a]phenothiazin2-one.