Total synthesis of the supposed structure of (-)-sclerophytin A and an improved route to (-)-7-deacetoxyalcyonin acetate

[reaction: see text]Stereoselective acid-catalyzed rearrangement of 15-->16 is the central step in total syntheses of (-)-7-deacetoxyalcyonin acetate (1) and the compound with the alleged structure of sclerophytin A (2). Since tetracyclic diether 2 is not identical to sclerophytin A, the structure of this antineoplastic marine diterpene must be revised. The conversion of 15-->16 demonstrates for the first time that tetrahydrofurans containing (Z)-1-methylalkenyl side chains can be prepared by Prins-pinacol rearrangements.     

Synthesis of (-)-7-epiaustraline and (-)-1-epicastanospermine

Highly efficient and selective syntheses of the title compounds are described. The cornerstone of the synthetic plan is the tandem inter [4 + 2]/inter [3 + 2] cycloaddition process. These syntheses differ from previous applications of this strategy in that they incorporate an alkylation in the hydrogenolysis step to close the second ring of the azabicyclic systems. Notable features of the sequence are (1) the highly regio- and stereoselective [3 + 2] cycloaddition of nitronate 15 with siloxymethyl (Z)-beta-silylvinyl ketone (Z)-22b and (2) the highly selective reduction of the resulting ketone 24a with L-Selectride. A single-crystal X-ray structure analysis of synthetic (-)-7-epiaustraline confirmed that the targeted structure was successfully synthesized. This stimulated a reexamination of the structural assignment of the natural product. (-)-1-Epicastanospermine was synthesized in four steps from the common intermediate 27a. The absolute configuration of (-)-1-epicastanospermine was assured by single-crystal X-ray structure analysis of intermediate (-)-27a. Thus, the sign of the optical rotation had to be revised. The overall efficiency of these syntheses were 9 steps and 23% yield for (-)-7-epiaustraline and 10 steps and 20% yield for (-)-1-epicastanospermine     

The parent of 2-(4,5-dihydro-1H-tetrazol-5-ylidene)-2-cyanoacetate: Synthesis and reactivity X-ray structure of (E)2-[1-(2,2-dimethylpropyl)-4,5-dihydro-1H-tetrazol-5-ylidene]-2-cyanoacetate

Reaction of 3,3-diazido-2-cyanoacrylate 5 with four moles of ammonia gives tetrazolyl-bisammonium salt 7 . The key-intermediate is the amino-vinyl azide 6 which spontaneously undergoes a 1,5′ ring-closure reaction followed by double deprotonation. Treatment of 7 with hydrochloric acid yields the parent of 2-(4,5-dihydro-1H-tetrazol-5-ylidene)-2-cyanoacetate 9 (R = Me, Et) as the only tautomer. Regiospecific monoalkylation of bisammonium salt 7a with dimethyl sulfate and reaction of ammonium salt 12 with hydrochloric acid gives (E)2-(1-methyl-4,5-dihydro-1H-tetrazol-5-ylidene)-2-cyanoacetate ( 13 ) (X-ray structure of derivative 14 ). Compound 13 can also be obtained from vinyl azide 10 and methylamine. This experiment as well as AM1 calculations of 9a, 23 and 24 strongly favour tautomer 9a .     

Synthesis of 1-(1,1-dimethylethyl)-1H-pyrazole-4-carboxylate ester derivatives

Attempts to prepare ethyl 5-cyano-1-(1,1-dimethylethyl)-1H-pyrazole-4-carboxylate ( 7 ) by the reaction of the corresponding 5-chloro derivative 1b with cyanide ion were unsuccessful. The chloro ester was synthesized from the corresponding amino ester la utilizing nonaqueous diazotization with nitrosyl chloride. An alternate process was developed which allowed the preparation of 7 from the corresponding 5-methyl ester 3 in four steps. The structure of the N-methylamide 8 synthesized from 7 was confirmed by X-ray diffraction analysis.     

Synthesis and structure determination of isomeric 7- and 8-chloro-1,5-benzodiazepine derivatives

Reaction of 4-chloro-1,2-benzenediamine with 3,3-dimercapto-1-phenyl-2-propen-1-one afforded, as expected, a mixture of 7-chloro and 8-chloro-1,3-dihydro-4-phenyl-2H-1,5-benzodiazepine-2-thione. After separation of the two components and further reaction, their structure was established by chemical degradation of 7-chloro-2-(2-diethylaminoethylthio)-4-phenyl-3H-1,5-benzodiazepine to 5-chloro-1,3-dihydro-1-methyl-2H-benzimidazol-2-one. The structure was also confirmed by single X-ray analysis of 7-chloro-2-(2-diethylaminoethylthio)-4-phenyl-3H-1,5-benzodiazepine.     

Radiation study on polymer - matrix composite materials

The present study is on the effect of γ radiation on the electroconductivity of two polymer - matrix composite materials and their application.When the absorption dose came to the peak value dose 6×10⁴Gy, the electroconductivity of the graphite - PM-MA composite materials reached a peak value of 14 s · m^-1.The electroconductivity of the copper - PMMA composite material decreased with the increase of the absorption dose in the range of 4.0×10⁴ to 7.5×10⁴Gy and then kept stable at about 2.5×10^-5s · m^-1.The two composite materials were analysed by infrared spectrum, microphotography and XPS. The two composite materials are of amosphous structure. The two composite materials show excellent properties of polarogram. They can be used in polarographic analysis as solid electrode. Graphite - polymethyl methacrylate can be powdered and mixed with plastics, rubber or coating as antistatic electric material.     

Synthesis and crystal structure of 2-{5-[2-(2,6-dichlorophenylamino)benzyl]-4-p-tolyl-4H-1,2,4-triazol-3-ylthio}acetate

The compound 2-{5-[2-(2,6-dichlorophenylamino)benzyl]-4-p-tolyl-4H-1,2,4-triazol-3-ylthio}acetate has been prepared and characterized by IR, ¹H NMR, ¹³C NMR and mass spectra. The crystal and molecular structure were further confirmed using single crystal X-ray diffraction. The crystal structure has been found to be stabilized by intermolecular C–H···O interaction generating bifurcated hydrogen bonds whereas the C–H···N interactions generate chain of molecules. The intramolecular N–H···N hydrogen bond forms a ring with S(7) graph-set motif.     

Reaktion von 3-(Dimethylamino)-2H-azirinen mit 1,3-Thiazolidin-2-thion

Reaction of 3-(Dimethylamino)-2H-azirines with 1,3-Thiazolidine-2-thione Reaction of 3-(dimethylamino)-2H-azirines 1 and 1,3-thiazolidine-2-thione ( 6 ) in MeCN at room temperature leads to a mixture of perhydroimidazo[4,3-b]thiazole-5-thiones 7 and N-[1-(4,5-dihydro-1,3-thiazol-2-yl)alkyl]-N′,N′-dimethylthioureas 8 (Scheme 2), whereas, in i-PrOH at ca. 60°, 8 is the only product (Scheme 4). It has been shown that, in polar solvents or under Me₂NH catalysis, the primarily formed 7 isomerizes to 8 (Scheme 4). The hydrolysis of 7 and 8 leads to the same 2-thiohydantoine 9 (Scheme 3 and 5). The structure of 7a, 8c , and 9b has been established by X-ray crystallography (Chapt. 4). Reaction mechanisms for the formation and the hydrolysis of 7 and 8 are suggested.     

4a,6-Bis-(N-methlanilino)-7-hydroxy-2,3,8-trimethyl-4a,9a-dihydro-xanthen-1,4-dion: Ein thermolyseprodukt von 6-(N-methylanilino)-7a-methyl-3a,7a-dihydroindazol-4,7-dion

Summary 4a,6-Bis-(N-methylanilino)-7-hydroxy-2,3,8-trimethyl-4a,9a-dihydro-xanthene-dione (4) was obtained by thermolysis of 6-(N-methylanilino)-7a-methyl-3a,7a-dihydroindazol-4,7-dione (1) The structure was determined on basis of 1D- and 2D-NMR techniques.Herrn Prof. Dr. G. Zigeuner zum 70. Geburtstag gewidmet     

Synthesis and Characterization of 1,2-Benzylidenedioxy-7-(2-hydroxybenzylideneamino)-4-azaheptane and Its Complexes with Transition Metals

1,2-Benzylidenedioxy-7-(2-hydroxybenzylideneamino)-4-azaheptane was synthesized by reaction of 1,2-benzylidenedioxy-3-chloropropane with 1,3-diaminopropane and subsequent condensation of 1,2-benzylidenedioxy-7-amino-4-azaheptane with salicylaldehyde. Complexes of 1,2-benzylidenedioxy-7-(2-hydroxybenzylideneamino)-4-azaheptane with cobalt(II), nickel(II), and copper(II) salts were obtained. The structure of the ligand and its complexes was established on the basis of their elemental compositions, IR, UV, and ¹H NMR spectra, magnetic susceptibilities, and thermogravimetric data.     

The effect of 6- and 7-substituents on the structure and tautomeric conversions of 3,3-dimethyl-1-(4,4-dimethylcyclohexa-2,6-dion-1-yl)-3,4-dihydroisoquinoline

The crystalline and molecular structure of 3,3-dimethyl-6,7-dimethoxy-1-(4,4-dimethylcyelohexa-2,6-dion-1-yl)-3,4-dihydroisoquinoline (I) have been determined. The effects of 6- and 7- substituents on the structure and tautomeric conversion of 3,3-dimethyl-1-(4,4-dimethylcyclohexa-2, 6-dion-1-yl)-3, 4-dihydroisoquinoline in solution have been studied by IR, electronic, x-ray electronic, and NMR spectroscopy and using quantumchemical calculations in the MNDO/H approximation. It was found that I exists in the enamine-diketone tautomeric form in the crystalline state and in solution. The 6- and 7- substituents cause a change in molecular conformation and a corresponding redistribution of electron density.Russian University of National Friendship, Moscow 117198. N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow 117000. Institute of Technical Chemistry, Ural Section, Russian Academy of Sciences, Perm' 614600. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 922–933, July, 1995. Original article submitted April 15, 1995.     

Synthesis of the sialic acid (-)-KDN and certain epimers from (-)-3-dehydroshikimic acid or (-)-quinic acid

(-)-3-Dehydroshikimic acid (3-DHS, 4), a C(7)-building block now available in large quantity from corn syrup, has been converted into the sialic acid (-)-KDN (3) as well as its C-7- and C-8-epimers. (-)-Quinic acid can be used for the same purpose. [structure: see text]     

Synthesis of N-substituted 9-[2-(3,4-methylenedioxyphenyl)-2-oxoethyl]-1,5-dinitro-7,8-benzo-3-azabicyclo[3.3.1]non-7-en-6-ones

Aminomethylation has been accomplished of the anionic Yanovskii adduct of 2,4-dinitronaphthol and 3,4-dimethylenedioxyacetophenone. The structure of the 3-substituted 9-[2-(3,4-methylenedioxyphenyl)-2-oxoethyl]-1,5-dinitro-7,8-benzo-3-azabicylo[3.3.1]non-7-en-6-one was determined by two-dimensional homo-and heteronuclear correlation spectroscopy. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, 1382–1389, September 2007.     

5-Phenyl-2-(pyrazol-4-yl)-1,3,4-thiadiazoles

By recyclization of 2-R-6-ethyl-7-hydroxy(methoxy)-3-(5-phenyl-1,3,4-thiadiazol-2-yl)chromones when treated with hydrazine hydrate and phenylhydrazine, we synthesized 5-phenyl-2-(3-R-5-R1-1H-pyrazol-4-yl)-1H-1,3,4-thiadiazoles and 2-(3-R-5-R1-1-phenyl-1H-pyrazol-4-yl)-5-phenyl-1H-1,3,4-thiadiazoles. We confirmed the structure of the latter from ¹H NMR spectra.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 781–787, May, 2005.     

Radical carboxyarylation approach to lignans. Total synthesis of (-)-arctigenin, (-)-matairesinol, and related natural products

[reaction: see text] Total syntheses of seven biologically important lignan natural products, including (-)-arctigenin, (-)-matairesinol, and (-)-alpha-conidendrin, by way of a highly stereoselective domino radical sequence is presented. The reported stereochemistry of the natural product 7-hydroxyarctigenin is shown to be erroneous; a diastereoisomeric structure is assigned to the natural product.     

Synthesis and Crystal Structure of a Luminescent Compound 5-（1H-benzoimidazol-2-yl）- 3H-[ 1,2,3 ] triazole-4-carboxylic Acid

The title compound, 5-(1H-benzoimidazol-2-yl)-3H-[1,2,3]triazole-4-carboxylic acid (C10H7N5O2·C3H7NO, Mr=302.30), has been synthesized and characterized by FT-IR and ESI-MS, 1 H-NMR spectroscopy and X-ray single-crystal diffraction. Crystal structure of the title compound was grown from DMF by slow diffusion at room temperature. Crystal data: orthorhombic structure, space group Pna21 with a=6.9635(3), b=19.4398(7), c=30.6165(12), V=4144.5(3)3, Z=12, Dc=1.454 g/cm 3, μ(MoKα)=0.108 mm-1, and F(000)=1896. The structure was refined to R=0.0450 and wR=0.0975 for 3578 observed reflections with I>2σ(I). The intermolecular hydrogen bonds and π-π stacking further stabilize the structure.     

Synthesis and spectral properties of 2-methylthio-3H-4-(para-substituted-phenyl)-7-[(o-, and p-substituted)-phenylthio]-1,5-benzodiazepines

A series of twelve new 2-methylthio-3H-4-(p-substituted phenyl)-7-[(o-, and p-substituted)phenylthio]-1,5-benzodiazepines, which have potentially useful pharmacological properties, has been synthesized by condensing the 3,3-dimercapto-1-(para-substituted-phenyl)-2-propen-1-one with 3,4-diamino phenyl-R-phenylthio ethers, and subsequently the 1H-1,5-benzodiazepine-2-thiones obtained were treated with sodium hydride and methyl iodide. The structure of all products was corroborated by ir, ¹H-nmr, ¹³C-nmr and ms.     

The study of cis - and trans -2 butene using mass spectrometry

Using mass spectrometric technique, the effect of geometrical isomerism on the first and higher appearance energy values for C₄H₃ ⁺, C₄H₇ ⁺ and C₃H,₃ ⁺ ions obtained from cis-2-butene andtrans-2-butene is reported. The structure in the ionization efficiency curves (studied for 9 eV above threshold) for the same ions obtained from the two isomers is reported and compared. It is believed that at threshold C₄H₇ ⁺ fragment is formed from the two isomers as methallyl ion. For C₃H₃ ⁺ fragment formed from the cw-isomer at threshold the proposed structure is the propargyl ion with ΔH_f equal to 279-4 kcal/mole while for that ion obtained fromtransisomer the proposed structure is the allenyl ion with ΔH_f equal to 296.6 kcal/mole.     

Synthesis and Crystal Structure of 1-(o-methylphenyl)-2-(p-methoxyphenyl)-1,3,2-diazaphospholidin-4-thione-2-sulfide

11NTRODUCTIoNThederivativesofdiazaphospholidinoneorthecorrespondingthionesareknowntopossessinterestingbiologicalproperties,suchasherbicidalactivity"'2i.Inrecentyears,itwasreportedthatthel,4,2-diazaphospholindine-5-thione-2havegoodselectiveherbicidalactivity"'41.Tolookformoreeffectiveherbicideswithlowtoxicity,aseriesofnovel1-(o-methylphenyl)-2-(p-methoxyphenyl)-phospholidin-4-thione-sulfideshavebeensynthesizedandtheirmolecularstructuresstudied.PreliminarybioassaysshowthatthesecomPoundshaveg…     

The absolute configuration of the (−)-RSp-enantiomer of cyclo-1-(1′-dimethylaminoethylferrocene)-2-(acetylacetonato)palladium

Conclusions The structure and absolute configuration of (–)-RS_p-cyclo-1-(1-dimethylaminoethylferrocene)-2-(acetylacetonato)palladium have been determined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1528–1534, July, 1979.