Über die absolute Konfiguration der Cantharsäure und des Palasonins

The absolute configurations of (+)-cantharic acid, a chiral derivative of the achiral insect defensive substance cantharidin ( 1 ), and of palasonin, a lower homologue of 1 occurring in the plant Butea frondosa, were shown to be represented by formulas 2 and 3 , respectively (scheme 1). These results were obtained by application of the Horeau method (table 1) on the (+)-cantharic acid derivatives (+)- 5 , (?)- 7 , and (?) 11 (scheme 2), and the palasonin derivatives (+)- 29 and (+)- 30 (scheme 4), as well as by comparison of the chiroptical properties (tables 2 and 3) of a number of derivatives, prepared from either cantharic acid or palasonin. – Attempts to incorporate various radioactively labelled precursors into palasonin ( 3 ), using young and adult plants, have been so far unsuccessful.     

Über die Synthese der Pilocarpus-Alkaloide Isopilosin und Pilocarpin,sowie die absolute Konfiguration des (+)-Isopilosins

A novel synthesis for rac-pilosinine ( 6 rac) and transformation of (+)-pilosinine ( 6 ) into the pilocarpus alkaloids (+)-isopilosine ( 9 ) and (+)-pilocarpine ( 18 ) are described. By correlation via 5 with 18 the absolute configuration of (+)-isopilosine ( 9 ) is established.     

Über die Temperaturabhängigkeit der 13C-NMR.-Spektren von [5–6-η-(1Z, 5E)-Cyclooctadien]tetracarbonyleisen und (1Z, 5E)-Cyclooctadien

On the Temperature Dependence of the ¹³C-NMR. Spectra of [5-6-η-(1Z,5E)-Cyclooctadien] and of (lZ, 5E)-Cyclooctadiene The activation parameters of the conformational ring inversion process (simultaneous rotation around the C(3), C(4) and C(7), C(8) bonds; cf. Scheme 1) of the title compounds ( 1 and 2 , respectively) have been determined between 275 L and 155 K by a complete line shape analysis of the temperature dependent proton noise-modulated decoupled ¹³C-NMR. spectra of 1 and 2 . The temperature dependence of the rates (k( 1 ) and k( 2 ), respectively) of the inversion process can be described by the following equations (no influence of the solvents was observed; E_a in J/mol): . Further data are given in Tables 1 and 2. The carbonyl groups of the complex 1 show at 180 K , where the ring inversion process is frozen out, a single line at 211 ppm, i. e. the coalescence temperature of the carbonyl groups must be < 180 K .     

1H- und 13C-NMR.-Spektren von 6-(p-X-Phenyl)fulvenen. Kurzmitteilung

¹H- and ¹³C-NMR.-spectra of 6-(p-X-phenyl)fulvenes The ¹H- and ¹³C-NMR.-spectra of a series of 6-(p-X-phenyl)fulvenes 3 , measured at 9.39 T (93.9 kgauss), have been analyzed. In these compounds, electronic effects due to the substituent X clearly exert changes in chemical shifts as well as in coupling constants in the 5-membered ring. Small changes in bond length are observed by comparison of the vicinal ¹H, ¹H-coupling constants, whereas changes in charge densities linearly influence the chemical shifts of C(5), C(2) and C(3).     

Über die Synthese von 1-Aryl-und 1-Alkyl-2, 3-dimethyl-chinoxalinium-perchloraten. 2. Mitteilung. Synthese und 1H-NMR.-Spektren von 2,3-Dimethyl-1-phenyl-6-X-chinoxalinium-perchloraten

On the Synthesis of 1-Aryl- and-1-Alkyl-2, 3-dimethyl-quinoxalinium Perchlorates. 2nd Communication

1 1. Mitt.: [1].

. Synthesis and ¹ H-NMR. Spectra of 2, 3-Dimethyl-1-phenyl-6-X-quinoxlinium Perchlorates The synthesis of the title compounds ( 5 ) which have been useful as precursors for a lot of conventional and new-type dyes [2-8] has yet been limited to examples with X?H [2] [3] [11] [15] and with electron-donating [4] [12] or at best slightly electron-accepting [1] [6] substituents X and R. We now describe a method suitable even for compounds 5 with strongly electron-accepting substituents: N-monosubstituted o-phenylendiamines 4 , were condensed with 2, 3-butanedione and perchloric acid in mixed solvents containing an excess of diethyl ether. The products - mostly substituted at position 6 of the quinoxalinium ring - are chracterized by ¹H-NMR. spectra, elemental analyses and in most cases by isolation of the corresponding bases 6 . Correlations of chemical shifts with Hammett's σ_p [18] are given by equations (1)-(5).     

Über die thermische,katalytische und photochemische Stickstoff-Eliminierung des 1-Diazo-3-(1-methylcyclopenta-2,4-dienyl)-2-propanons

The Thermal, Catalytic, and Photochemical Denitrogenation of 1-Diazo-3-(1-methylcyclopenta-2,4-dienyl)-2-propanone The synthesis of the title compound 12 is described. This diazoketone, distinguished by its C_s-symmetry and by a built-in cisoid diene unit, gives 5-methyltricyclo[3.3.0.0^2,8]oct-6-ene-3-one ( 13 ) when subjected to thermal or catalytic denitrogenation with rhodium (II) acetate or copper (II) acetylacetonate. Direct irradiation of 12 at 350 nm causes Wolff rearrangement, whereas the benzophenone-sensitized photolysis gives again ketone 13 . A 1,4-carbene or carbenoid addition was never observed under the conditions described. The ketone 13 equilibrates thermally or under base catalysis with 1-methyltricyclo[3.3.0.0^2,8]oct-6-ene-3-one ( 17 ). The key step of this apparent CH₃ migration is shown to be a Cope rearrangement of the corresponding enols (hydroxysemibullvalenes).     

Über Pterinchemie. 71. Mitteilung. Trennung der Diastereomeren (6R)- und (6S)-5,6,7,8-Tetrahydro-L-neopterin

Separation of the Diastereomers (6R) and (6S)-5,6,7,8-Tetrahydro-L -neopterin The mixture of the diastereomers of the pentaacetylderivative IV of (6RS)-5,6,7,8-tetrahydro-L -neopterins could be separated by fractional crystallisation in methanol into the diastereomers IV A and IV B. Hydrolysis with hydrochloric acid gives the pure, diastereomeric, (6R)- and (6S)-5,6,7,8-tetrahydro-L -neopterins.     

1H-NMR.-, 13C-NMR.-, UV.- und CD.-Daten von synthetischem (3S, 3′S)-Astaxanthin,seinem 15-cis-Isomeren und einigen analogen Verbindungen

¹H-NMR., ¹³C-NMR., UV. and CD. spectral data of synthetic (3S, 3′S)-astaxanthin, its 15-cis isomer, and some related compounds ¹H-NMR., ¹³C-NMR., UV. and CD. spectra are reported for synthetic (3S, 3′S)-astaxanthin ( 1 ), its 15-cis isomer ( 2 ), its diacetate ( 3 ), and the 15, 15′-didehydro compound ( 5 ). These data prove the identity of the synthetic and the naturally occuring compound 1 . A full interpretation of the ¹H- and ¹³C-NMR. spectra is given and confirms the configuration of all the double bonds. The conformation of the cyclohexene end group of all the compounds is shown to be identical. The signs of the different CD. maxima of 15-cis-astaxanthin are found to be opposite to those of the all-trans compound.     

Über 3,3,6,9,9-Pentamethyl-2,10-diaza-bicyclo-[4.4.0]-1-decen und einige seiner Derivate. Über synthetische Methoden. 13. Mitteilung

3,3,6,9,9-Pentamethyl-2,10-diaza-bicyclo[4.4.0]-1-decen and some of its derivatives A simple synthesis for the bicyclic amidine 1 (Scheme 3) is described. This base and the salts which were prepared from it show solubility characteristics which make the amidine a potentially useful reagent for salt formation of carboxylic acids and related proton complexes of bidentate ligands. Among the derivatives made from 1 are the sterically strongly hindered N-alkylated amidines 11 , 12 and 14 (Scheme 5), as well as the stable crystalline N¹-oxidoamidine-N²-oxyl radical 2 (Scheme 6). The ability of the latter to serve as a paramagnetic chelating ligand for metal ions is illustrated by the preparation of a corresponding nickel(II) complex. The radical is also a source for the α-nitronyl-nitrosonium cation 4 which shows in its reactivity towards conjugated dienes and olefines some of the expected resemblance to singlet oxygen.     

Über die Stereochemie der Hydrogenolyse von N-Benzyl-Bindungen II. Die Deuteriolyse von chiralem N,N-Dimethyl-phenylglycin und die Konfiguration von (+)-Phenyl-essigsäure-2-d1

The steric course of the hydrogenolytic cleavage of benzyl-N-bonds using Pd-C catalyst was determined by deuteriolysis of R(?)-N,N-dimethyl-phenylglycine I, which gave (+)-phenylacetic acid containing 70% of the monodeutero compound. The configuration of (+)-phenylacetic acid-2-d₁ was determined (S) and its optical purity estimated by Schmidt degradation to chiral S(+)-benzylamine-α-d₁. On the basis of these results, hydrogenolysis of I can be evaluated to proceed by 80% inversion and 20% retention of configuration. Methyl N,N-dimethyl-phenyl-glycinate yielded racemized methyl phenylacetate-2-d₁.     

Über die Synthese von Tris(trimethylsilyl)silyl-kalium, -rubidium und -caesium und die Molekülstrukturen zweier Toluolsolvate

About the Synthesis of Tris(trimethylsilyl)silyl Potassium, Rubidium and Cesium and the Molecular Structures of two Toluene Solvates . Solventfree tris(trimethylsilyl)silyl potassium ( 1 ), rubidium ( 2 ) and cesium ( 3 ) are obtained by the reaction of the zink group bis[tris(trimethylsilyl)silyl] derivatives with the appropriate alkali metal in n-pentane. Addition of benzene or toluene to the colourless powders yields deeply coloured solutions. From these solutions single crystals of tris(trimethylsilyl)silyl rubidium—toluene (2/1) ( 2 a ) and tris(trimethylsilyl)silyl cesium—toluene (2/3) ( 3 a ) suitable for X-ray structure analysis are iso- lated [ 2a : orthorhombic; P2₁2₁2₁; a = 1 382.1(3); b = 1 491.7(5); c = 2 106.3(6) pm; Z = 4 (dimers); 3a : orthorhombic; P2₁2₁2₁; a = 2 131.0(6); b = 2 833.1(2); c = 925.2(2) pm; Z = 4 (dimers)]. The central structure moieties are folded four-membered Rb₂Si₂ and Cs₂Si₂ rings, respectively. Small Si? Si? Si angles (100 to 104°) on the one hand and extreme highfield ²⁹Si-NMR shifts of the central silicon atoms on the other hand indicate a strong charge transfer from the alkali metal atoms to the tris(trimethylsilyl)silyl fragments, i.e. mainly ionic interactions between alkalimetal and silicon atoms.     

Über die Umlagerung von Benzo[b]-1, 4-thiazepinen und 1, 4-Thiazepinen

The rearrangement of differently substituted 1, 4-thiazepines under various reaction conditions has been investigated. 2-Phenyl-4-methylthio-benzo [b]-1, 4-thiazepine ( 3 ) and 2-phenyl-benzo [b]-1, 4-thiazepine-4 (5H)-thione ( 2 ) extrude sulfur under the catalytic influence of bases and rearrange into 2-methylthio-4-phenyl-quinoline ( 4 ) and 4-phenyl-thiocarbostyril ( 6 ) respectively. Under the same conditions, 2-phenyl-4-methylthio-2, 3-dihydro-benzo [b]-1, 4-thiazepine ( 11 ) rearranges to 2-styryl-benzothiazine ( 12 ), whereas the dioxide 18 shows no tendency to rearrange. 2,7-Diphenyl-hexahydro-1,4-thiazepine-5-one( 19 ) could be converted into 2-styryl-5-phenyl-2-thiazoline ( 20 ) by treatment with polyphosphoric acid. The possible mechanisms of these rearrangements are discussed.     

Über Tris(siloxymethyl)-, Tris(silylmercaptomethyl)- und Tris(silylmethyl)amine

By the reaction of alkali salts of triorgano-silanols, -silanethiols and trimethylsilylmethanol as well as of triorganosilyllithium compounds with tris(chloromethyl)amine, silyl derivatives of tris(hydroxymethyl)-, tris(mercaptomethyl)- and tris(methyl)amine were prepared.     

Über Chalkogenolate. 184. Bis(thiocarbamoyl)- und Bis(N-methylthiocarbamoyl)sulfane

On Chalcogenolates. 184. Bis(thiocarbamoyl)- and Bis (N-methylthiocarbamoyl)sulfanes The sulfanes (H₂N? CS? )₂S₂ and (CH₃? NH? CS? )₂S_x with x = 1 and 2 have been characterized by means of electron absorption, infrared, nuclear magnetic resonance, and mass spectra. The decomposition of the N-methyl substituted compounds has been studied kinetically at 20°C in ethanolic solution.     

Über die Temperaturabhängigkeit der 13C-NMR.-Spektren von Tetracarbonyl (η-(Z)-cycloocten)eisen und (Z)-cycloocten

On the Temperature Dependence of the ¹³C-NMR.-Spectra of Tetracarbonyl (η-( Z )-cyclooctene)iron and of ( Z )-Cyclooctene Reaction of (Z)-cyclooctene (1) with Fe₂(CO)₉ in pentane at 0° yielded tetracarbonyl(η-(Z)-cyclooctene)iron (2) as a yellow oil which can be stored over a longer period only at ?78°. It is shown that the title compounds ( 1 and 2 , respectively) are fluxional. The activation parameters for the conformational C-atom site exchange of (Z)-cyclooctene (1) and tetracarbonyl (η-(Z)-cyclooctene)iron (2) (in CCl₂F₂) have been determined between 113 K and 151 K for 1 and between 151 K and 205 K for 2 , respectively, by a complete line shape analysis of the temperature dependent proton noise-decoupled ¹³C-NMR. signals of the olefinic C-atom. The kinetic data and activation parameters are given in Tables 1 and 2.     

Bildung,Kristallstruktur und absolute Konfiguration von (−)-N-(Chloromethyl)galanthaminium-chlorid

Formation, X-Ray Crystal Structure, and Absolute Configuration of (?)-N-(Chloromethyl)galanthaminium Chloride The acetylcholinesterase inhibitor galanthamine ( 1 ), main alkaloid of several Narcissus species, readily forms a quaternary ammonium salt by reaction with the solvent CH₂Cl₂. The structure and absolute configuration of (?)-N-(chloromethyl)galanthaminium chloride ( 2 ) were determined by X-ray diffraction (R = 0.075 for 2775 observed independent reflexions) and NMR spectroscopy. The tetragonal crystals (space group P4₃) contain two crystallographically independent cations which do not differ significantly from one another. The CH₂Cl group is attached to the quaternary N-atom in stereospecific (R)-configuration. In the crystal, the configurational position of the Me group at the N-atom of 2 differs from that of the crystalline free base 1 . Hydrogen bonding is observed from the OH group at C(3) of 2 to the Cl^? anion or to the Cl-atom of an adjacent cation.     

Über die Synthese und spektroskopische Charakterisierung von Strontium‐ und Bariumtetrabromoferrat(III) und die Kristallstruktur von Ba(FeBr4)2

Preparation and Spectroscopic Characterization of Strontium and Barium Tetrabromoferrate(III) and the Crystal Structure of Ba(FeBr₄)₂ The synthesis of the hitherto unknown bromoferrates(III) of alkaline‐earth metals was carried out by heating mixtures of the metals or the binary bromides together with bromine at temperatures of 450 °C and pressures of up to 1500 bar in closed quartz ampoules. The attempts have been successful only with the larger cations of Sr and Ba. In the case of Be, Mg, and Ca only mixtures of the binary bromides with FeBr₃ could be received. By analysis of the Raman and electronic spectra the dark red compounds of Sr and Ba have been characterized as ternary tetrabromoferrates(III) containing tetrahedral FeBr₄ anions. The composition M(FeBr₄)₂ (M = Sr, Ba) has been determined by potentiometric and titrimetric analysis and thermal degradation by thermogravimetry. A single crystal structure determination of Ba(FeBr₄)₂ confirmed the spectroscopic assignments. The orthorhombic crystal structure (space group Pbca; a = 13.054(3) Å; b = 11.093(2) Å; c = 21.764(4) Å; Z = 8) consists of FeBr₄ and BaBr₉ polyhedra.