Stability of 7,8‐Dihydropterins in Air‐Equilibrated Aqueous Solutions

6‐Substituted 7,8‐dihydropterins (=2‐amino‐7,8‐dihydropteridin‐4(1H)‐ones) are heterocyclic compounds that occur in a wide range of living systems and participate in relevant biological functions. In air‐equilibrated aqueous solutions, these compounds react with dissolved O₂ (autooxidation). The rates of these reactions as well as the products formed strongly depend on the chemical structure of the substituents. 7,8‐Dihydro‐6‐methylpterin and 7,8‐dihydro‐6,7‐dimethylpterin that bear electron‐donor groups as substituents are the most reactive derivatives and undergo oxidation of the pterin moiety to yield the corresponding oxidized derivatives (6‐methylpterin and 6,7‐dimethylpterin, resp.). The oxidations of 7,8‐dihydrobiopterin, 7,8‐dihydroneopterin, and 7,8‐dihydrofolic acid are slower, and they yield 7,8‐dihydroxanthopterin as the main product. 7,8‐Dihydroxanthopterin, 6‐formyl‐7,8‐dihydropterin, and sepiapterin are rather stable, and their consumption in air‐equilibrated solutions is negligible for several days. The pseudo‐first‐order rate constants of the reactions between these compounds and O₂ at 25° and 40° are reported. The biological implications of the results obtained are also discussed.     

Electrochemical thiocyanation of dodecahydro-7,8-dicarba-<Emphasis Type="Italic">nido</Emphasis>-undecaborate and 7,8-dimethyldecahydro-7,8-dicarba-<Emphasis Type="Italic">nido</Emphasis>-undecaborate monoanions

Electrochemical thiocyanation of the dodecahydro-7,8-dicarba-nido-undecaborate and 7,8-dimethyldecahydro-7,8-dicarba-nido-undecaborate monoanions afforded thiocyanate derivatives of these compounds, which were isolated as alkylammonium salts. The structures of the synthesized compounds were determined by the data from IR, ¹H and ¹¹B NMR, and ¹¹B-¹¹B NMR COSY spectroscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1553–1556, July, 2005.     

Synthesis and Biological Activity of Cyanoethyl Derivatives of Fusidic Acid

3,11-Dihydroxy and 3,11-dioxo triterpenoids of the fusidane series reacted with acrylonitrile in 1,4-dioxane in the presence of alkali and phase-transfer catalyst to give mono- and bis(2-cyanoethoxy) and 2-cyanoethyl derivatives. The reaction with 3,11-dioxo analog afforded 2,2-disubstituted derivative as a result of addition of two cyanoethyl groups to the α-position with respect to the C³=O carbonyl group. The isolated compounds were screened for antibacterial and antifungal activities.

     

Antioxidant properties of 2,4-diphenyl-7,8-benzo-5,6-dihydro(4H)selenochromene and 2-<Emphasis Type="Italic">para</Emphasis>-chlorophenyl-4-phenyl-7,8-benzo-5,6-dihydro(4H)selenochromene

The antioxidant properties of 2,4-diphenyl-7,8-benzo-5,6-dihydro(4H)selenochromene and 2-para-chlorophenyl-4-phenyl-7,8-benzo-5,6-dihydro(4H)selenochromene were studied using the initiated oxidation of ethylbenzene and propan-2-ol as model reactions. The antioxidant activity of these compounds was quantitatively characterized by the apparent rate constant of inhibition, fk _in. Addition of 2,4-diphenyl-7,8-benzo-5,6-dihydro(4H)selenochromene to ethylbenzene being oxidized increases the chemiluminescence intensity.     

Chemical Constituents from the Stems of Mahonia Japonica

A new dihydroberberine alkaloid, 7,8‐dihydro‐8‐methoxyberberine ( 1 ), along with six known compounds including two dihydroberberine alkaloids, 7,8‐dihydro‐8‐hydroxyberberine ( 2 ) and oxyberberine ( 3 ) and four protoberberine alkaloids, berberine ( 4 ), palmatine ( 5 ), jatrorrhizine ( 6 ) and columbamine ( 7 ), were isolated from the stems of Mahonia japonica. These compounds were characterized and identified by physical and spectral evidence.     

A new method for the synthesis of novel 3-substituted 4-amino-8-ethoxycarbonylpyrazolo[5,1-c][1,2,4]triazines and pyrazolo[1′,5′:3,4][1,2,4]triazino[5,6-b][1,5]benzodiazepines

Novel 3-substituted 4-amino-8-ethoxycarbonylpyrazolo[5,1-c][1,2,4]triazines 7,8 were synthesized by the reactions of malononitrile and ethyl cyanoacetate with the pyrazole-5-diazonium salt 3 . Moreover, compounds 7,8 were converted into the pyrazolo[1′,5′:3,4][1,2,4]triazino[5,6-b][1,5]benzodiazepines 9, 10 .     

Pyrimidotetrathiafulvalenes. 2. Trimethylsilylation of 5,-dioxo(4H, 6H)-1,3-dithiolo-[4,5-d]pyrimidine-2-selone and the use of the silylated product for the synthesis of 2,4-dioxopyrimidotetrathiafulvalenes

The trimethylsilylation of 5,7-dioxo(4H,6H)-1,3-dithiolo[4,5-d]pyrimidine-2-selone with bis(trimethylsilyl) acetamide enables pyrimido-tetrathiafulvalene derivatives to be prepared in benzene solution and increases the yield of the target compounds compared with the reaction of the unsilylated selone in DMF solution. The intermediate 2,4-bis(trimethyl-silyloxy)pyrimidotetrathisfulvalenes were sensitive to hydrolysis. The previously undescribed [2,4-dioxo(1H,3H)pyrimido]di-(methylthio)tetrathifulvalene has been obtained. The redox properties of the compounds obtained have been investigated by cyclic current-potential measurements.Riga Technical University, Riga LV-1658. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1285–1289, September, 1994. Original article submitted July 25, 1994.     

Isolierung und Strukturaufklärung von 36 Diterpenoiden aus Trichomen von Plectranthus edulis (VATKE) T.T. AYE

Isolation and Structure Elucidation of 36 Diterpenoids from Leaf-Glands of Plectranthus edulis (VATKE ) T.T. AYE Analysis of the polar diterpenoids from the yellow glands of the title plant from Kenya and Abyssinia led to the identification of several novel abietanoids. Main compound is the known edulon A ( 40 ), a 5(4→3) abeo-abietane. Minor compounds include 6 different royleanones, 15 spirocoleons, 3 vinylogous quinones, 8 acylhydroquinones (as their 6,7-dioxo compounds or the tautomeric disophenols), 2 naphthaquinones (as the 1,10-seco-abietanoids), and deacetyledulon A. The known coleon-A-lactone (37) now has also been found in Plectranthus edulis. The intermediacy of the γ-enollactol 44 , combined with a leaving group on C(3) is postulted to explain the biogenesis of the unusual 4H-5-oxaaceanthrylen skeleton of edulon A.     

Synthesis of 7,8-dihydro-6H-pyrazolo[3,4-b]quinolin-5-ones and related derivatives

This paper describes the synthesis of a new series of 4-amino-1-(unsubstituted and chloro or fluoro substituted benzyl)-7,8-dihydro-6H-pyrazolo[3,4-b]quinolin-5-ones 8 and the corresponding 7,8-dihydro-6H,9H-pyrazolo[3,4-b]quinoline-4,5-diones 13 . The derivatives obtained by reaction of these compounds with sodium azide in concentrated sulfuric acid are also reported.     

New Epoxy‐Substituted Nitrogenous Bisabolene‐Type Sesquiterpenes from a Hainan Sponge Axinyssa sp.

Two new uncommon epoxy‐substituted nitrogenous bisabolene‐type sesquiterpenes, 3‐formamido‐7,8‐epoxy‐α‐bisabolane ( 4 ), 3‐isocyano‐7,8‐epoxy‐α‐bisabolane ( 5 ), together with three known related sesquiterpenes, 1 – 3 , were isolated from the Hainan sponge Axinyssa sp. Their structures were determined on the basis of extensive spectroscopic analyses and by comparison of their NMR data with those of structurally related compounds.     

Reaction of α-Haloketones with ortho-Dihydroxy-2H-1-benzopyran-2-ones. Formation of α-Pyrano-1,5-benzodioxapines-A New Heterocyclic System

Reaction of 7,8-dihydroxy-2H-1-benzopyran-2-one, and its 4-methyl derivative, with α-haloketones affords α-pyrano-1,5-benzodioxapines, while 3-chloro-4-methyl-7,8-dihydroxy-2H-1-benzopyran-2-one gives α-pyrano-1,4-benzodioxane. The structures of the compounds were deduced using a combination of ¹H nmr, ¹³C nmr (BB, DEPT), HETCOR, NOESY, and selective INEPT techniques and molecular modeling.     

Two New C19‐Diterpenoid Alkaloids with Anti‐inflammatory Activity from Aconitum iochanicum

Two new C₁₉ ‐diterpenoid alkaloids, 7,8‐epoxy‐franchetine ( 1 ) and N(19)‐en‐austroconitine A ( 2 ), were isolated from Aconitum iochanicum . Compound 1 was a new C₁₉ ‐diterpenoid alkaloid with a 7,8‐epoxy unit. Their structures were elucidated by comprehensive spectroscopic analyses including UV , IR , MS , 1D and 2D NMR . Biological activity tests indicated that two new compounds exhibited inhibitory activity against nitric oxide (NO ) production in LPS ‐activated RAW264 .7 macrophages. Compared with positive control, the two new compounds showed weak anti‐inflammatory effects with the inhibition rate of 27.3% and 29.2%, respectively.     

Synthesis of 4- and 6-methyl derivatives of 5,7-dioxo(4h,6h)-1,3-dithiolo[4,5-d]pyrimidine based on methylbarbituric acids,spectroscopic characteristics and acidity constants

We have obtained previously unknown 1-methyl- and 1,3-dimethyl-5-diethylaminothiocarbonylthiobarbituric acids by reaction of sodium diethyldithiocarbamate with 5-phenyliodonium betaines of 1-methyl- and 1,3-dimethylbarbituric acids. Cyclization of these compounds upon heating in conc. H₂SO₄ gives methyl-substituted 5,7-dioxo(4H,6H)-1,3-dithiolo[4,5-d]pyrimidine-2-diethylimmonium hydrosulfates; the derivative of 1-methylbarbituric acid forms a mixture of 4-methyl- and 6-methyl-substituted compounds (21). We isolated perchlorates of 4-methyl- and 4,6-dimethyl-substituted derivatives in pure form. By treatment of the immonium salt with sodium sulfide or selenide, we obtained 4-methyl- and 4,6-dimethyl-5,7-dioxo(4H,6H)-1,3-dithiolo[4,5-d]pyrimidine-2-thiones and 4-methyl-, 6-methyl-, and 4,6-dimethyl-2-selenones. We characterized the isomeric 4- and 6-methyl-substituted selenones by electronic absorption spectra and ionization constants (7.65 and 4.0). The differences in the pK values and in the electronic absorption spectra makes it possible to distinguish the substitution site in N-mono-substituted derivatives of 5,7-dioxo(4H,6H)-1,3-dithiolo[4,5-d]pyrimidine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1526–1533, November, 1993.     

Some derivatives of pyrimido [5,4-b]quinoline

10-Chloro-2,4-dioxo derivatives of pyrimido[5,4-b]quinoline have been synthesized, and nucleophilic substitution reactions in these compounds have been studied.     

Alloxazines and isoalloxazines. Mass spectrometric analysis of riboflavin and related compounds

The positive ion electron-impact mass spectra of a series of alloxazines, iso-alloxazines and some derivatives have been examined. The compounds employed were lumichrome (7,8-dimethylalloxazine), 1,3-dimethyllumichrome, lumiflavin (7,8,10-trimethyl-iso-alloxazine), 3-methyllumiflavin, riboflavin [7,8-dimethyl-10-(D-1′-ribityl)-iso-alloxazine], riboflavin tetraacetate, 3-methylriboflavin tetraacetate and riboflavin tetrapropionate. By using exact mass measurements, metastable ion defocusing and the mass/composition shifts occurring with derivatives, it has been possible to arrive at detailed interpretations of the mass spectra of all compounds. With lumichrome and lumiflavin, fragmentation commences by elimination of HNCO from the pyrimidine ring. With riboflavin and its derivatives the ribityl chain cleaves off first, followed by decomposition of the iso-alloxazine ring. Application of these methods and findings to the structural analysis of chemically interesting modified flavins is predicted to be rewarding.     

Synthesis of 3-isocyano-nido-7,8-dicarbaundecaborate salts and their use as new isonitrile ligands in transition-metal complexes

The treatment of 3-isocyano-o-carboranes with an alkali solution in alcohol results in the regioselective splitting out of a boron atom from position 6 of theo-carborane nucleus to give 3-isocyano-nido-7,8-dicarbaundecaborate salts, in which the isonitrile group is attached to the boron atom of thenido-polyhedron anion. 3-Isocyano-nido-7,8-dicarbaundecaborate salts are new isonitrile ligands in transition-metal complexes. Complexes with chromium, molybdenum, tungsten, and iron compounds have been obtained.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1458–1460, August, 1993.     

Sesquiterpenoids, alantolactone analogues, and seco-guaiene from the roots of Inula helenium

Three new sesquiterpenoids, a new unusual dimeric eudesmanolide, bialantolactone, a new nor-eudesmanolide, trinoralantolactone, and a new seco-guaiene, 7S,1(10)Z-4,5-seco-guaia-1(10),11-diene-4,5-dioxo, together with 13 known sesquiterpenoids, were isolated from the roots of Inula helenium. Their structures were elucidated by comprehensive spectroscopic analyses. The absolute configurations of bialantolactone and 7S,1(10)Z-4,5-seco-guaia-1(10),11-diene-4,5-dioxo were defined via the experimental and computational optical rotation and CD data. The plausible biosynthetic pathways to bialantolactone and 7S,1(10)Z-4,5-seco-guaia-1(10),11-diene-4,5-dioxo are discussed. 16 compounds were evaluated for their anti-bacterial activities against six bacteria.     

Flavonoid Aglycones and Indole Alkaloids from the Roots of Acacia Confusa

From the methanolic extract of the roots of Acacia confusa Merr. (Leguminosae), (‐)‐2,3‐cis‐3,4‐cis‐4′‐methoxy‐3,3′,4,7,8‐pentahydroxyflavan ( 1 ), (‐)‐2,3‐cis‐3,4‐cis‐3,3′,4,4′,7,8‐hexahydroxyflavan ( 2 ), (‐)‐2,3‐trans‐3′,4′,7,8‐tetrahydroxydihydroflavonol ( 3 ), (+)‐catechin ( 4 ), (‐)‐epicatechin ( 5 ), 3′,4′,7,8‐tetrahydroxyflavonol ( 6 ) together with N‐methyltryptamine ( 7 ) and N,N‐dimethyltryptamine ( 8 ) were isolated, and their structures were established by analysis of their spectroscopic data. Among them, compound 1 was a new flavonoid. Additionally, the results of chromatographic bioassay on lettuce seeds indicated that compounds 7 and 8 exhibited significant phytotoxicity at a concentration lower than 14 mM.     

Synthesis and Study of the Properties of 7,8-Polymethyleneimidazo[4,5-d]-1,3,2-diazaphosphorin-2-thiones

In thionation of cyclic N-cyanoamidines, a four-step process occurs that leads to derivatives of novel heterocyclic systems: 7,8-polymethyleneimidazo[4,5-d]-1,3,2-diazaphosphorin-2-thiones. We have studied the chemical and spectral properties of the compounds obtained.     

Metal Complexes of Phthalocyanine Structural Analogs with Oxygen- or Nitrogen-containing Heterorings. Synthesis and Properties

Nucleophilic substitution of the bromine atom and nitro group in 4-bromo-5-nitrophthalodinitrile and reduction of 4-benzoylamino-5-nitrophthalodinitrile gave, respectively, tribenzo[b,e,g][1,4]dioxocine-7,8-dicarbonitrile and 2-phenylbenzimidazole-5,6-dicarbonitrile. These compounds were used to synthesize new structural analogs of phthalocyanine, having oxygen- and nitrogen-containing heterorings, (tetratribenzo[b,e,g][1,4]dioxocino[7,8-b,g,l,q]-5,10,15,20-tetraazaporphyrinato)copper(II) and (23,73,123,173-tetraphenyl-tetrabenzimidazolo[5,6-b,g,l,q]-5,10,15,20-tetraazaporphyrinato)cobalt(II). Spectral properties of the resulting complexes were studied.