Bis-thiolurethane aus α,ω-Alkandithiolen und Isocyanaten

Biscarbamothioates from α,ω-Alkanedithiols and Isocyanates Sixty biscarbamothioates 1 were prepared by triton-B catalyzed addition of α,ω-alkanedithiols to isocyanates. Some of the products were investigated for biological activity.     

Nitroketenaminale, 9. Mitt.: Zur Umsetzung von α,β-ungesättigten Aldehyden mit Nitroketenaminalen

Nitroketeneaminals, IX: Reaction of α,β-Unsaturated Aldehydes with Nitroketeneaminals Reaction of α,β-unsaturated aldehydes 1a , b with nitroketeneaminal 2a in boiling acetic acid leads to 2-amino-3-nitropyridines 4 unsubstituted at C-6. By refluxing 1a and 2a in alcohol/acetic acid or in alcohols, respectively, 2-alkoxy-1,2,3,4-tetrahydropyridines 7a and 8a are obtained. The reaction of 1a and 2b yields 5-alkoxy-2,3,4,5,6,7-hexahydroimidazo[1,2-a]pyridines 7b and 8b . By ¹H-NMR spectroscopy the relative configuration of 7aC, 7aT, 7bC , and 7bT can be determined.     

Synthese von 3-methylenmonosubstituierten 2-Oxo-tetrahydrofuranen durch Umsetzung von α-Keto-γ-lactonen mit Wittig-Reagenzien

Synthesis of 3-Methylenetetrahydrofuran-2-ones from α-Keto-γ-lactones with Wittig Reagents The synthesis of the 3-methylenetetrahydrofuran-2-ones 3a--q from the α-keto-γ-lactones 1a,b and the Wittig compounds 2a--h is described.     

Adduktbildung und Dimerisierung von α-Piperidinoacetonitril bei Umsetzung mit n-Butylmagnesiumchlorid. V. Mitt. über Umsetzungen von α-Aminonitrilen

Dimerisation of α-Piperidinoacetonitrile in the Reaction with n-Butylmagnesium chloride The reaction mechanisms which determine the course of the reaction between t- and n-butyl-magnesium chloride and α-piperidinoacetonitrile, have been studied. The formation of different quantities of the reaction products 3-amino-2,4-dipiperidinocrotononitrile and butyl-α-piperidinomethylketone can be explained on the basis of steric hindrace and also through the difference of nucleophilic activity of t- and n-butyl groups.     

Massenspektrometrische Untersuchungen an isomeren α,β- und β, γ-ungesättigten Ketonen mit raumerfüllenden Substituenten

A Mass Spectrometric Study on Isomeric α,β- and β,γ-Unsaturated Ketones with Bulky Substituents The mass spectra of the α,β- and β,γ-unsaturated ketones 1-4 (scheme 1) are very different depending on the stereochemistry of the double bond. The E-configurated ketone 2 predominantly shows McLafferty fragmentation, whereas Z-configurated ketone 1 reveals ?-cleavage. In the β, γ-unsaturated ketones 3 and 4, mainly loss of the pertinent allyl radical by α-cleavage was observed.     

Synthese von γ,γ'-Dihydroxysulfonen und γ-Hydroxy-γ'-ketosulfonen

Syntheses of γ,γ'-Dihydroxysulfones and γ-Hydroxy-γ'-ketosulfones Reduction of γ,γ'-diketosulfones 1 with dimethylaminoborane leads to γ,γ'-dihydroxysulfones 3 via γ-hydroxy-γ'-ketosulfones 2 . The influence of substituents on the ratio of the yields of 2 and 3 is investigated.     

Reaktionen α,β-ungesättigter γ-Oxosulfone mit Nucleophilen

Reactions of α,β-Unsaturated γ-Oxosulfones with Nucleophiles Bromination of the γ-oxosulfones 1 and subsequent dehydrohalogenation leads to the α,β-unsaturated γ-oxosulfones 3 . These products react with primary and secondary amines to yield the enaminoketones 7 . γ-Oxobissulfones 10 are formed from 3 by addition of the sulfinic acids 9 . Thioles 11 react with 3 to give the γ-oxomercaptosulfones 12 or the thioacetals 14 .     

Improved method for the synthesis of Nα-9-fluorenylmethyloxycarbonyl-Nδ,ω bis-adamantyloxycarbonyl-L-arginine

A modified method is reported for the prepartion of N^α-9-fluorenylmethyloxycarbonyl-N^δ,ω bis-adamantyloxycarbonyl-L-arginine, giving an overall yield of 60% over three steps based on N^α-benzyloxycarbonyl-L-arginine. Commercially available adamantyl fluoroformate for guanidine function protection of N^α benzyloxycarbonyl-L-arginine, catalytic transfer hydrogenation with formic acid on palladium black for removal of the benzyloxycarbonyl protecting group, and fluorenylmethylsuccinimidyl carbonate for the final synthesis, were introduced to simplify and reduce the cost of preparation of this arginine derivative. The reaction conditions have been accurately studied at each step in order to optimize the yields.     

Addition von β-Dicarbonylverbindungen an 2-Acetyl-p-benzochinon, 3. Mitt.1): Untersuchung der Umsetzung mit α-Hydroxymethylencycloalkanonen

Addition of β-Dicarbonyl Compounds to 2-Acetyl-p-benzoquinone, III¹⁾: The reaction of α-hydroxymethylenecyclopentanone 2 with acetylquinone 1 yields the spiro-compound 3 . α-Hydroxymethylenecyclohexanone 7 gives the dibenzopyran 8 and the spiro-compound 9 as by-product. Compounds 3, 8 , and 9 are labile, rearrangement to 6 and 11 is examined by NMR spectroscopy. Acetylation of 6 and 11 yields 5 and 12 . With hydrochloric acid the spiro-compounds 6, 11 are rearranged to 16 and 17 , respectively.     

Die Kondensation von γ-und δ-Oxo-carbonsäureester mit 1,2-, 1,3- und 1,4-Alkylendiaminen

Condensation of Esters of γ- and δ-Oxocarboxylic Acids with Alkylene-1,2,1,3- and 1,4-diamines. Esters of γ-and δ-Oxocarboxylic acids condense with alkylene-1,2-, 1,3-, and 1,4-diamines and yield bicyclic lactams (5) . The path of the reaction was studied by spectroscopic methods using ethyl levulinate and N-methyl-propylene-1,2-diamine. The first step is the formation of an “aminalester” by reaction of the CO-group of ethyl levulinate with alkylene diamine, followed by intramolecular ring closure.     

Umsetzung von Iminiumsalzen mit 4-Benzylamino-1,2-naphthochinonen und unerwarteter Effekt in den 1H-NMR-Spektren von Piperidiniumchloriden

Reaction of Iminium Salts with 4-Benzylamino-1,2-naphthoquinones and an Unexpected Effect in the ¹H-NMR-Spectra of Piperidinium Chlorides The 4-aralkylamino substituted 1,2-naphthoquinones 1 – 5 react under defined conditions with methyleniminium salts to the protonated 3-aminomethyl derivatives 6 – 22 . NMR examination of 16·HCl shows the equatorial piperidinium protons in β position resonating at higher field than the axial ones. This reversal in chemical shift was also observed for N-methyl- and N-benzylpiperidinium chloride.     

Zur Umsetzung von Trialkylsulfonyldiamiden mit 2-Chlor-1-dimethylaminopropan und 3-Chlor-1-ethylpiperidin

Reactions of N,N,N′-Trialkylsulfonyldiamides with 2-Chloro-N,N-dimethylpropanamine and 3-Chloro-1-ethylpiperidine Sodium N,N,N′-trimethylsulfonyldiamide (1) was reacted with 2-chloro-N,N-dimethylpropanamine to yield the isomers 2 and 3 which were separated by column chromatography. The reactions of 1 and 4 with 3-chloro-1-ethylpiperidine gave only one isomer each, namely 6a and 6b .     

Analysis of γβ, βγ, γγ, ββ continuous turns in proteins

Abstract: We report the observation of continuous turns in proteins which comprise individual γ‐turns or β‐turns or both that are situated immediately one after the other along the polypeptide chain. The continuous turns were identified from a representative data set of three‐dimensional protein crystal structures. The γβ/βγ, γγ and ββ continuous turns represent peptides of varying amino acid residue lengths and conformations. The continuous turns frequently observed in proteins were: γβ, between a coil and a strand; βγ, between a helix and a strand; γγ, between coils; and ββ, either between a strand and a coil or between strands or coils. We determined the statistically significant amino acid residue preferences at individual positions in the turn, calculated amino acid positional potentials and analyzed main chain hydrogen bonds and side‐chain interactions likely to stabilize the continuous turns. The data on continuous turns have been integrated in the database of structural motifs in proteins (DSMP) on our web server at ( http://www.cdfd.org.in/dsmp.html ). This is useful to make queries on sequences compatible with different continuous turns.     

Analysis of γβ, βγ, γγ, ββ multiple turns in proteins

Abstract: The number of γ‐turns in a representative protein dataset selected from the current Protein Data Bank has increased almost seven times during the past decade. Eighty percent classic γ‐turns and 57% inverse γ‐turns are associated as multiple turns with either another γ‐turn or a β‐turn. We refer to these as multiple turns of the (γβ)_1,2,3 or (βγ)_1,2,3 type, depending upon whether the γ‐turn is before or after the β‐turn along the protein chain, respectively. However, for multiple turns involving only γ‐turns, we follow the nomenclature analogous to that proposed earlier for the multiple (or double) β‐turns. Fifty‐eight per cent β‐turns are associated as multiple turns with another β‐turn. We extracted multiple turns from the protein dataset and classified them on the basis of individual γ‐ or β‐turn types and the number of overlapping residues. Furthermore, we evaluated the amino acid positional potentials and determined the statistically significant amino acid preferences, hydrogen bond/side‐chain interaction preferences in the multiple turns and secondary structure preferences for residues immediately flanking these turns. The results of our analysis would be useful in the modeling, prediction or design of multiple turns in proteins. The amino acid sequence corresponding to the multiple turn, position in the protein chain, PDB Code/chain in which multiple turn is present and the individual turn types constituting the multiple turns are available from our website and this information would also be integrated in our Database of Structural Motifs in Proteins ( http://www.cdfd.org.in/dsmp.html ).     

Über die Umsetzung von Δ1-Pyrrolinen mit aktivierten Alkinen

On the Reaction of Δ¹-Pyrrolines with Activated Alkynes Indolizines and their partially hydrogenated derivatives are usually synthesized by reacting 2-picolines with α-halogenated carbonyl compounds. In this paper a new synthetic approach is described: the reaction of 2-substituted Δ¹-pyrrolines with alkynyl-carbonyl compounds leading to tetrahydroindolizines and Δ¹-pyrrolinylalkynes.     

α-Alkylmercapto- und α-Arylmercapto-alkylisocyanate

α-Alkylmercapto- and α-Arylmercapto-alkylisocyanates α-Alkylmercapto- and α-arylmercapto-alkylisocyanates 2 were prepared from α-halosulfides 1 by reaction with silver cyanate. With ammonia, primary or secondary amines they give the corresponding α-mercaptoalkyl-ureas 4 ; with alcohols, the α-mercaptoalkylurethans 3.