Synthese von Nucleosiden aus 2-substituierten Imidazolen

Synthesis of 2-Substituted Imidazole Nucleosides Condensation of the trimethylsilyl derivatives of 2-substituted diethyl and dimethyl imidazole-4,5-dicarboxylates ( 3–5 and 7–9 ) with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D -ribofuranose ( 2 ) in the presence of trimethysilyl trifluoromethanesulfonate provided the 2-substituted diethyl and dimethyl 1-(2′,3′, 5′-tri-O-benzoyl-β-D -ribofuranosyl)imidazole-4, 5-dicarboxylates 10–15 . These were treated with ammonia to afford the 2-substituted 1-(β-D -ribofuranosyl)imidazole-4,5-dicarboxamides 16–21 . Treatment of 2-methyl-( 16 ) and 2-ethyl-1-(β-D -ribofuranosyl)imidazole-4,5-dicarboxamide ( 17 ) with fuming nitric acid in oleum at ?30° yielded the nitric acid esters 23 and 24 . Besides the esterification of the sugar hydroxyl groups one H-atom of the imidazolecarboxamide function at C(5) in these nucleosides was also substituted by the NO₂ group. The conformations in solution of 16 and 23 have been determined by ¹H- and ¹³C-NMR. spectroscopy. These studies indicate that the nucleosides exist in dimethyl-sulfoxide solution preferentially in the S-gg-syn-conformation ( 16 ) and N-gt-conformation ( 23 ). In the crystal structure of nucleoside 23 , the ribose was found to be in the O(1′)_endo, C(1′)_exo twist conformation. The conformation about C(4′), C(5′) is gauche-trans and the molecule exists in the syn form.     

Über den sterischen Verlauf der Umsetzung von Enaminen aus offenkettigen Aldehyden und Ketonen mit Nitroolefinen zu 2,3-disubstituierten 4-Nitroketonen

On the Steric Course of the Reaction of Enamines Derived from Open-Chain Aldehydes and Ketones with Nitro-olefins Yielding 2,3-Disubstituted 4-Nitroketones The relative configuration of the nitro-ketone 12 obtained by the title reaction has been proved by a Baeyer-Villiger degradation and subsequent reduction to the amino-alcohol (±)-(u)- 20 , the relative configuration of which is identical with a sample prepared from 2-methyl-3-hydroxybutyrate of known configuration (Scheme 1). The stereochemical course of the title reaction is thus as predicted by our topological rule. It is assumed that the other nitro-ketones 13–18 described here are also formed by (lk)-combination of the trigonal centers of the educts (diastereoselectivity > 90%, see Formulae and Fig. 1). It is not possible to reverse this relative topicity by employing (Z)- instead of (E)-components of the starting materials, due to the reversibility of the primary step of these Michael additions (Schemes 2 and 3, and Fig. 2).     

Synthese von 1-substituierten 4-Amino-2(1H)-pyridinthionen durchDimroth-Umlagerung aus 2,4-Diaminothiopyranyliumhalogeniden

4-Amino-2-alkylimino-2H-thiopyranes (5) and 4-amino-2-alkylaminothiopyranylium halogenides (4) resp. on heating in refluxingDMFA are rearranged in the presence of Na-ethylate to 1-alkyl-4-aminodihydro-2(1H)-pyridinethiones (2). Also 2-methylthiothiopyranylidenammonium iodides (6) and 2-methylthio-4H-thiopyrane-4-one (7) can be transformed into 1-substituted 2(1 H)-pyridinethiones (2) by heating in prim. amines. On treatment with alkali. 4-dimethylaminothiopyranylium iodide (4 a) is transformed into its base5 a and hydrolyzed to8. 5a and8 are rearranged to the pyridinethiones2 a and the tautomers9 A,B. The structure of the rearranged pyridinethiones2 was proved by the1-phenylderivate2 a. Thus 4-methyl-3-penten-2-on reacts with phenylthiourea via the phenylimino-1,3-thiazine (14) to give 3-phenyl-2(1H)pyridinethione (15).15 is transformed by themethylpyrimidine-pyridine-rearrangement to the 1-phenylpyridinethione2 a. The mechanism of theDimroth-reaction of 2-alkylimino-2H-thiopyranes (5) and the stereochemistry of the1-benzyl-6-phenyl-2(1H)-pyridinethiones2 are discussed.     

Notiz zur Synthese von Alkyl-, Cycloalkyl- und Aryl-(4-aminophenyl)-sulfonen

Syntheses of Some Alkyl-, Cycloalkyl- and Aryl-(4-aminophenyl)-sulfones Syntheses of (4-aminophenyl)-alkyl, -cycloalkyl and -aryl sulfones 2 were achieved both by alkylation of 4-(acetylamino)-benzenesulfinic acid ( 7 ) to the corresponding acetanilides 9 followed by hydrolysis and by oxidation of the appropriate (4-nitrophenyl)-sulfides 11 to (4-nitrophenyl)-sulfones 1 with subsequent Béchamp reduction.     

4-Phenylthiosemicarbazid als Reagens zur Charakterisierung von Aldehyden und Ketonen

Ohne ZusammenfassungMeinem verehrten Lehrer, Frau Prof. Dr. Ing. M.Perpar, sage ich auch an dieser Stelle für die erfahrene Hilfe herzlichen Dank.     

Thermische Cyclodehydratisierung von Salicylalkoholen; eine einfache Synthese von 4-substituierten 2H-Chromenen

Heating of 1-(o-hydroxyaryl)-2-propen-1-ols ( 9–13 ; see scheme 1) in diglyme solution at 147° leads to a 1,4-elimination of water to yield ω-vinyl-o-quinomethides ( b ; see scheme 2) as intermediates which cyclise rapidly to form 2H-chromenes ( 17–21 ). 1-(o-Hydroxyphenyl)-5-hexen-1-ol ( 14 ) on heating at 147° is transformed into o-(1,5-hexadienyl)-phenol ( 23 ). This phenol rearranges at higher temperature (270°) in N,N-diethylaniline to yield a mixture of 2,4-propanochromane ( 25 ) and cis- and trans-3,4-propanochromane (cis- and trans- 26 ). The kinetically controlled ratio of these compounds is 2,8:1:2,9. The formation of 25 and 26 can be explained by an intramolecular Diels-Alder reaction (see scheme 3).     

Bis(trimethylsilyl)-hypophosphit und Alkoxycarbonylphosphonigsäure-bis(trimethylsilyl)ester als Schlüsselsubstanzen für die Synthese von Organophosphorverbindungen

Bis(trimethylsilyl)hypophosphite und Alkoxycarbonylphosphonous Acid Bis(trimethylsilyl) esters as Building Blocks in Organophosphorus Chemistry The oxidation of pure bis(trimethylsilyl)hypophosphite ( BTH ) with chalcogenides forming (Me₃SiO)₂P(X)H (X = O, S, Se, Te) is described as well as its reactions with alkylhalides RX (X = Cl, Br, I) and Cl? C(O)OR (R = Me, Et, Bzl). By reaction with oxygen, sulfur, and selenium the alkoxycarbonylphosphonous acid bis(trimethylsilyl)esters form RO? C(O)? P(X)(OSiMe₃)₂ (X = O, S, Se) whereas with Cl? C(O)OR the bis(alkoxycarbonyl)-phosphinic acid trimethylsilylesters are obtained. After partial hydrolysis the resulting instable RO? C(O)? P(O)H(OSiMe₃) gives RO? C(O)? P(O)(OSiMe₃)? CH₂? NH? A? COOR′ (A = CH₂, CH₂CH₂, CHCH₃, CH₂CH₂SH, CHCH(CH₃)₂,…) when allowed to react with hexahydro-s-triazines of the aminoacid esters. Reactions of the alkoxycarbonyl-P-silylesters with NaOR or NaOH result in the corresponding mono-, di-, or trisodium salts. With mineral acids decarboxylation occurs, but H? P(O)(OH)? CH₂? NH? A? COOH can be obtained, too. The structure of the compounds described are discussed by their n.m.r. data.     

Synthese von 4,4-disubstituierten 1,3-Thiazol-5(4H)-thionen

Synthesis of 4,4-Disubstituted 1,3-Thiazol-5(4H)-thiones An easy synthesis for the 1,3-thiazol-5(4H)-thiones 5 , a class of heterocycles which have hitherto only been available with difficulty, is described. Reaction of 3-amino-2H-azirines 25 with thiocarboxylic acids at 0° yields monothiodiamides of type 20 (Scheme 6) which, on treatment with Lawesson reagent at 100°, undergo thiation and cyclization to give 5 in good yield.