Substituierte 3-Amino-thiophene und 3-Amino-selenophene aus β-Chlor-α-cyan-zimtsäurenitril

Summary -Chloro--cyano-cinnamonitrile (1) reacts in one step with -oxo-thioles3 or successively with sodium sulphide and -chlorocarbonyl compounds4 to form the 5-substituted 4-amino-2-phenyl-thiophene-3-carbonitriles5. Analogously, the successive reactions of -chloro cinnamonitrile1 with sodium selenide — produced in situ from selene and sodium boronhydride — and -chlorocarbonyl compounds4 yields the 5-substituted 4-amino-2-phenyl-selenophene-3-carbonitriles6.

     

Die Acetalgruppe, 1. Mitt. Acetale von Halogenmethyl-arylcarbinolen

Several halomethyl-arylcarbinols were prepared, and the influence of substituents on enantiomer selectivity in the acetalisation reaction with [2S-(2,3a,4,7,7a)]-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-ol was examined.

Unserem sehr verehrten Lehrer, Herrn Prof. Dr.Otto Hromatka, mit den besten Wünschen zum 80. Geburtstag gewidmet.     

Zur Kenntnis der gemeinsamen Einwirkung von elementarem Selen und gasförmigem Ammoniak bzw. Ethylenimin auf Ketone

Elemental sulfur reacts with ketones and gaseous ammonia at room temperature yielding thiazoline-3 in excellent yields. Under the same conditions elemental selenium does not react at all. Attempts using the known techniques which have been applied in improving the reactivity of slowly reacting ketones in thiazoline-3-synthesis have been unsuccessful (Exp. No. 1–17). The reaction of -halogenketones with sodiumhydrogenselenide to synthesize -hydroselenoketones gives only the original ketones and selenium in almost quantitative yields (No. 18–23). The same is observed with -haloketones and sodium ore magnesium-diselenides (No. 24–45). The explanation of these unexpected results is the strong reducing power of the hydrogenselenide (No. 46–52). Even -bromoketones with activated bromine (i.g. by phenyl groups) were reduced by sodiumhydrogensulfide giving red undefinite oils. However, -chloroketones give -mercaptoketones in excellent yields (No. 53–61). Hydrogenselenide reduces -mercaptoketones to sulfur and ketones in the presence of triethylamine (No. 62–67). Also the transformation of -selenocyanketones to ,-diketodisenides by alkali or the oxidative hydrolysis of selenium-BUNTE salts does not work and gives elementary selenium only. Studies about the concomitant reaction of elementary selenium and ethylenimine on ketones were continued (No. 68–82).

     

Elektrolyse substituierter Azidozimtsäure- und Azidoacrylsäureester

Several ring-substituted -azidocinnamic and -heterocyclic -azidoacrylic esters are subject to cathodic reduction under aprotic and protic conditions. Good to excellent yields of rather labile dehydroaminoacid derivatives resp. stableN,N-diacylated enaminoesters are selectively obtainable. The compounds are characterised by spectroscopic methods (¹H-NMR, IR, MS).

     

Circular Dichroism Spectra of 5- and 7-Bromo-6-ketosteroids

Circulardichroismspectra of 5- and 7-bromo-6-ketosteroidsof the cholestane and stigmastane serieswere studied. A negative Cotton effect corresponding to the n-* -transition of the ketone was observed in the CD spectra of 5-bromo-6-ketosteroids at 300 nm. The analogous Cotton effect was positive in CD spectra of 7-bromo-6-ketosteroids.     

Synthesis of α-alkyl- and α,α-dialkyl-β-phenyltryptamines

A new method was developed for the synthesis of -alkyl- and ,-dialkyl--phenyltryptamines based on alkylation of nitroalkanes with -phenyl-nor-gramine.     

Selective reduction of the acyl group in cyclic α-acyl-β-dicarbonyl compounds with sodium cyanoborohydride. Efficient synthesis of cyclic α-alkyl-β-dicarbonyl compounds

Efficient synthesis of cyclic -alkyl--dicarbonyl compounds of the cyclopentane, cyclohexane, tetronic acid, and -pyrone series from the corresponding cyclic -acyl--dicarbonyl compounds under the action of NaBH₃(CN) in a THF--HCl system is described.     

Condensation of ethyl α-ethoxymethyleneacylacetates withp-bromobenzoyl- and benzylidenehydrazines

Ethyl -ethoxymethyleneacetoacetate and -ethoxymethylenebenzoylacetate react with benzylidenehydrazine andp-bromobenzoylhydrazine to give hydrazones of the corresponding ethyl -formylacylacetates. It was established by¹H NMR and IR spectroscopy that hydrazones, which were obtained from benzylidenehydrazine, andp-bromobenzoylhydrazone of ethyl -formylacetoacetate exist in the ketoenamine (ketoenhydrazine) form, whereasp-bromobenzoylhydrazone of ethyl -formylbenzoylacetate exists in the enolimine (enolhydrazone) form.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2293–2296, September, 1996.     

Synthesis of driman-8α,11-diol from sclareol through 8α,12-epoxy-14,15-bisnorlabdan-13-one

A four-step synthesis of driman-8,11-diol from sclareol in 44% total yield is described that includes the intermediates (12R)-8,12-epoxy-14,15-bisnorlabdan-13-one, (12S)-8,12-epoxy-12-acetoxy-13,14,15,16-tetranorlabdane and 8,12-epoxy-13,14,15,16-tetranorlabd-11-ene.Institute of Chemistry, Academy of Sciences of the Republic of Moldova, Kishinev, fax (3732) 73 97 75, Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 124–125, March–April, 2000.     

Electrochemical oxidation of tetramethyl esters of α,α,ω,ω-alcaneteracarboxylic acids

Cyclization of esters of butane-1,1,4,4- and pentane-1,1,5,5-tetracarboxylic acids during electrolysis in methanol in the presence of Nal produces, with a yield of 95%, the esters of cyclobutane-1,1,2,2- and cyclopentane-1,1,2,2-tetracarboxylic acids. Under similar conditions, esters of the highest ,,,-alkanetetracarboxylic acids undergo iodation and hydroxymethylation due to electrical oxidation of methanol to formaldehyde. During electrolysis in methanol in the presence of NaOAc, the esters of ,,,-alkanetetracarboxylic acids undergo effective hydroxymethylation, followed by cyclization into substituted five- and six-member lactones, or tetrahydrofurans when structurally possible.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2332–2339, October, 1992.     

On the fate of biliverdin-IIIα-dimethyl ester formed by scrambling during syntheses of biliverdin-IXα-dimethyl ester from bilirubin

Summary In preparations of biliverdin-IX-dimethyl ester (2 b) from bilirubin-IX (1) the ratio of the XIII- and III-isomers3 b and4 b, formed via intermolecular scrambling, should be unity. However, irrespective of the synthetic variant considered, the amount of4 b obtained usually is exceptionally low. This is partly ascribed to a consecutive reaction of4 b in acidic methanol affording the chiral diastereomeric bridged biliverdins5 (a undb) and6 (a andb), respectively.

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Zum Verbleib des durch Scrambling gebildeten Biliverdin-III-dimethylethers bei Synthesen des IX-Isomeren aus Bilirubin

Zusammenfassung Bei der Darstellung von Biliverdin-IX-dimethylester (2 b) aus Bilirubin-IX (1) sollte das Verhältnis der durch intermolekulares Scrambling gebildeten XIII- und III-Isomeren3 b bzw.4 b eins betragen. Tatsächlich aber ist die Ausbeute an4 b, unabhängig von der verwendeten synthetischen Variante, immer sehr klein. Dieser Umstand läßt sich zumindest teilweise auf eine spezifische Reaktion von4 b in saurem Methanol zurückführen, in deren Verlauf die chiralen diastereoisomeren überbrückten Biliverdine5 (a undb) sowie6 (a undb) gebildet werden.

     

Complex formation between polyethylene oxide-containing nonionic surfactants and α- and β-cyclodextrins

The inclusion complexes based on polyethylene oxide (PEO)-containing nonionic surfactants and ()-cyclodextrins (CD) were synthesized. Their composition and crystal structure were studied. The inclusion complexes of the surfactants with -CD form a crystal structure similar to that of the -CD—PEO complex. The inclusion complexes of the nonionic surfactants with -CD form a structure similar to that of the -CD—PEO complex. The structural models of the crystalline complexes were proposed. The micelle-forming abilities of the surfactants in dilute solutions in the presence of CD were studied. The CD binding to a surfactant molecule in aqueous solutions begins from the PEO fragment. Possible reasons for the formation of inclusion complexes between noncomplementary surfactant and -CD molecules were discussed. The thermal stability was studied, and the possibility of thermal dissociation of the pseudo-complementary -CD—surfactant complexes was shown.     

Linear and cyclic N-acetyl-α-aryl-glycines: Synthesis and chemiluminescence studies

Summary A series of N-acetyl--arylglycines (IIa,IIb) was prepared by acid-induced electrophilic -amidoalkylation reactions; compounds of typeIIb were transformed into the corresponding 3-acetylaminobenzo[b]furan-2(3H)ones (III) by treatment with acetic anhydride. It was found that most of these new compounds (lactones as well as open chain derivatives) undergo base induced oxidation in the presence of oxygen with the emission of visible light. Preliminary structure-activity relationships for these novel chemiluminescence class are proposed.

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Lineare und cyclische N-Acetyl--aryl-glycine: Synthese und Chemilumineszenz-Untersuchungen

Zusammenfassung Eine Reihe von N-Acetyl--arylglycinen (IIa,IIb) konnte durch sauer induzierte elektrophile -Amidoalkylierung hergestellt werden; die Behandlung von Verbindungen des TypsIIb mit Acetanhydrid führte zu den entsprechenden 3-Acetylaminobenzo[b]furan-2(3H)onen (III). Es zeigt sich, daß die Mehrzahl dieser neuen Verbindungen (sowohl Lactone als auch offenkettige Derivate) bei basisch induzierter Oxidation mit (Luft-)Sauerstoff sichtbares Licht emittieren. Erste Struktur-Aktivitäts-Beziehungen für diese neue chemilumineszenzierende Klasse werden vorgeschlagen.

     

Strukturelle Abwandlungen an N-Acetylneuraminsäure, 25. Mitt.: Synthese von Methyl-2-α-glycosiden von 4-epi-, 7-epi-, 8-epi- und 7,8-bis-epi-N-Acetylneuraminsäure

The -methylketoside of N-acetylneuraminic acid methylester (4) is transformed via the deacetylated compound5 into the 9,8-O-isopropylidenderivative6 which could be oxidized regioselectively by RuO₄ to the corresponding 4-oxo-sialic acid analogue7. Reduction with the boraneammonia complex produces a 1:1 mixture of6 and the desired -methylketoside of 9,8-O-isopropyliden-4-epi-N-acetyl-neuraminic acid methylester (8). Removing of the isopropylidene group gives the -methylketoside of 4-epi-N-acetylneuraminic acid methylester (9), which was further transformed to the ammonium salt of 4-epi-N-acetylneuraminic acid -methylketoside (10). On the other hand compound5 was turned into the 4,8,9-tri-O-t-butyldimethylsilylderivative11 a from which the corresponding 7-oxo-compound12 by oxidation with RuO₄ derives. The reduction of12 with BH₃ - NH₃ yielded a 1:1 mixture of the starting material11 a and the desired 7-epi-derivative13 a which gives either via the purified peracetylated -methylketosid of 7-epi-N-acetylneuraminic acid methylester (14) or a direct saponification the sodium salt of 7-epi-N-acetylneuraminic acid--methylketoside (15).Applying the Königs-Knorr procedure to the peracetylated 8-epi-N-acetylneuraminic acid methylester (16) gives rise to the formation of a 1:1 mixture of the corresponding - and -methylketosides17 and18 besides traces of the corresponding 2,3-dideoxy-2,3-dideohydro-sialic acid derivative19. After chromatographic separation of17 further saponification leads to the sodium salt of 8-epi-N-acetylneuraminic acid--methylketoside (20). In an analogous procedure the sodium salt of 7,8-di-epi-N-acetylneuraminic acid--methylketoside (25) was prepared starting from the peracetylated 7,8-di-epi-N-acetylneuraminic acid methylester (21), whereby a mixture of the - and -methylketosides22 and23 was formed in a ratio 95:5 besides traces of the peracetylated 2,3-dideoxy-2,3-didehydrosialic acid methylester (24).

On study leave from the Department of Chemistry, Postgraduate and Research Center, R.B.N.B. College, Shrirampur-413709 (MS), India     

Electronic structure of monosubstituted benzenes and X-ray emission spectroscopy

The electronic structure of the benzaldehyde molecule has been studied by X-ray emission spectroscopy. The gas-phase O-K- and C-K-spectra of this compound have been obtained. MNDO quantum-chemical calculations have been carried out. The structure of the MO's of benzaldehyde has been compared with those of benzene and formaldehyde molecules. The character of the p-p interaction of the phenyl and formyl fragments has been considered. The contribution of the latter to the highest occupied molecular orbitals of the-system has been shown to be small.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1033–1037, June, 1994.     

Reaction of Pregnenolone and 3α,5-Cyclo-5α-pregnan-6β-ol-20-one with Trifluoroperacetic Acid

The reaction of pregnenolone and 3,5-cyclo-5-pregnan-6-ol-20-one with trifluoroperacetic acid produces the trifluoroacetates, hydrolysis of which gives the 3,5alpha;,6-triol.     

Convergent synthesis of 2′,3′-dideoxy-3′-mercapto nucleosides — Potential anti-HIV agents

Summary Methyl 3-benzoylthio-5-O-tert-butyldiphenylsilyl-2,3-dideoxy--D-erythro-pentofuranoside (4) and its corresponding anomer5 were synthesized in four steps from 2-deoxy-D-ribose and used as substrates for the synthesis of nucleosides by condensation with silylated thymidine and N⁶-isobutyryladenine. The nucleosides were deprotected by treatment with Bu₄NF inTHF followed by reaction with MeONa in MeOH to give 3-deoxy-3-mercaptothymidine (8), 2,3-dideoxy-3-mercaptoadenosine (15) and its corresponding anomer16. In the latter reactions it was important to use degassed solvents to minimize formation of the corresponding disulfides of purine nucleosides. Using Bu₄NF, without subsequent reaction with MeONa in the deprotection reaction, resulted in intermolecular transesterification reactions.On leave from Chemistry Department, Faculties of Science and Education, Tanta University, Tanta, Egypt     

Amino- und Hydroxylaminosubstituierte α-Azidozimtsäureester und α-Aminozimtsäureester durch kathodische Reduktion ungesättigter Nitroazidoester

Cathodic reduction of nitro-substituted azidocinnamic esters on mercury under aprotic and protic conditions was studied. Nitro and azido groups behave as independent entities so that selectively amino- resp. hydroxylamino--azido compounds are obtained, which could not be synthesised by conventional methods. Under aprotic conditions, with added acetic anhydride, medium yields of acylated 4-hydroxylamino- and 4-amino--cinnamic acid derivatives are isolated. Evidence of homogeneous electron transfer from nitroanion radicals to azido groups is given.

     

Nitrosation of mefenorex in the presence of cyclodextrins

- and -Cyclodextrin (CD) and heptakis-2,6-di-O-methyl--cyclodextrin (DIMEB) form soluble inclusion compounds with mefenorex (MEF); with -CD a partial inclusion occurs. No solid inclusion compound could be obtained with the four CDs. -, -CD and DIMEB, but not -CD, enhance the nitrosation rate of MEF if the nitrosation assay procedure (NAP test) is applied. During this reaction with - and -CD, solid inclusion compounds of the CDs and nitrosomefenorex (NMEF) precipitate.Part of the Ph.D. thesis of V. Wedelich, Freie Universität Berlin, 1985.     

Molecule-Responsive Fluorescent Sensors of α-Helix Peptides Bearing α-Cyclodextrin, Pyrene and Nitrobenzene Units in Their Side Chains

-Helix peptides bearing one unit of -cyclodextrin (-CD), one unit of pyrene and one unit of nitrobenzene (NB) in their side chains have been designed and synthesized as novel molecule-responsive devices.In both the CD-peptides, -PR17 and -PL17, the NB unit is separated from the CD unit by two turns of the helix. Two reference peptides (PL17, and -P17,) have also been synthesized. The circular dichroism studies in the peptide absorption region (200–250 nm)of -PR17 and -PL17 suggestthat the CD-peptides form stable-helixstructures (83–77%), which was destabilized by accommodating guest molecules (e.g., n-pentanol) into the CD cavity. It suggests that formation of intramolecular host–guest(CD–NB) complex stabilized thehelical structure and exogenous guest molecule excluded the appending NB moiety from inside to outside of the CD cavity, thereby causing destabilization of the helical structure and increasing the random coil content. The ICD spectra of the peptides in the pyrene and nitrobenzene absorption region (250–40 nm) suggest that NB forms inclusion complex with CD. The fluorescence studies revealed that the fluorescence of the pyrene unit is quenched by the NB unit in -PR17 and -PL17. The fluorescence intensity increases with increasing guest concentration for the CD-peptides.This guest-responsiveenhancement in the fluorescence intensity can be explained in terms of increased distance between the pyrene and NB moieties, which is caused by exclusion of the NB moiety from the CD cavity by guest accommodation. Using the guest-responsive fluorescence quenching properties of the CD-peptides, we have obtained binding constants for various short chain alkanols. -PL17 has higher binding affinity to the guest molecules than its isomer, -PR17, indicating that the location of functional groups on the peptide scaffold is important in molecule detection.