Bibliothek

Notizen: Syntheses of the four stereoisomeric dihydropalustramic acids ([6-(1-hydroxypropyl)-2-piperidyl]acetic acids)(-)-Dihydropalustramic acid, a key product in the structure elucidation of the alkaloid palustrin, has been assigned the threo-cis structure 20 by comparison with the four stereoisomeric (±)-dihydropalustramic acids (threo-cis, threo-trans, erythro-cis, erythro-trans). The latter were synthesized by a new route to α, α′-di-substituted piperidines of this type. Ring closure to the piperidine ring with simultaneous stereospecific formation of the hydroxylated side chain has been achieved by reaction of the stereoisomeric methylesters of 7,8-epoxy-2-decenoic acids with benzylamine. Assignment of the configuration at the piperidine ring is based on careful comparison of the H-NMR. spectra of the N-benzylpiperidines and with the help of lanthanide shift reagents.

Notizen: 1H-and13C-NMR. spectra of methyl esters of the diastereomeric (±)-dihydropalustramic acids; structural correlation of (-)-dihydropalustramic acid with the alkaloid palustrinUnambiguous assignment of cis-trans configuration at the piperidine ring of the four diastereomeric methyl esters of the (±)-dihydropalustramic acids is based on the interpretation of 1H- and 13C-NMR. data. (-)-Dihydropalustramic acid, the important degradation product of the alkaloid palustrin is shown to be threo-cis-[6-(1-hydroxypropyl)-2-piperidyl]acetic acid. The same conclusion holds for palustrin and dihydropalustrin. Therefore, palustrin is threo-cis-17-(1-hydroxy-propyl)-1,5,10-triazabicyclo[11.4.0]heptadec-15-en-11-one.

Notizen: Determination of the absolute configuration of alkaloids from Equisetum sp.,e.g. (+)-palustrin, palustridin ((+)-hydrochloride), and (-)-dihydropalustramic acid and derivativesThe absolute configuration of the title alkaloids has been determined using chiroptical methods (ORD., superposition of CD. values of appropriate models and a modified Horeau method). (+)-Palustrin is (13R, 17 S, 1′S)-17-(1-hydroxypropyl)-1,5,10-triazabicyclo [11.4.0]heptadec-15-en-11-on.

Notizen: Synthesis of threo-cis/threo-trans- and erythro-cis/erythro-trans-dihydropalustrinThe first synthesis of a threefold protected spermidine, namely 3-benzyloxycarbonyl-N1-phthaloyl-N2-tosylspermidin (9) is presented. Each of the protecting groups can be removed selectively. After hydrazinolysis the resulting N3-benzyloxy-carbonyl-N2-tosylspermidine (10) has been condensed with methyl (2 E)-cis-7,8-epoxy-2-decenoate to the threo-cis/trans piperidines 17, and with methyl (2 E)-trans-7,8-epoxy-2-decenoate to the erythro-cis/trans piperidines 17, respectively. After catalytic removal of the Z group, the resulting aminoesters 13 and 18, in a melt with imidazole, underwent ring closure to the 13-membered lactames 14 and 19, respectively. reductive deprotection of the N-tosyl group with sodium/ammonia led to the stereoisomeric palustrines 15 and 20, respectively.

Notizen: Degradation of palustrin to (-)-dihydropalustramic acid ((2R,6S,1′S)-[6-(1′-hydroxypropyl)-2-piperidyl]acetic acid), and the structure of palustrin and palustridinThe structure of the macrocyclic alkaloid palustrin is shown to be 1a. Its piperidine unit can be obtained as (-)-dihydropalustramic acid (6a) by the following sequence of degradation reactions (Scheme 1): catalytic hydrogenation of 1a followed by methylation and Hofmann degradation provides the allyl base 4. the regioselectivity of the Hofmann elimination is explained by intramolecular proton abstraction at C(3) by C(18)-O-. Catalytic reduction of 4 and subsequent acidic hydrolysis yielded 6a and N, N-dimethylputrescine (=N,N-dimethyl-1,4-butanediamine; 7). Loss of the N-alkyl group in the formation of 6a occurs during the catalytic hydrogenation step. This interpretation is supported by the results of model experiments. The position of the double bond in 1a is deduced from the IR. spectrum of the bromo-δ-lactone 19 prepared by treatment of 1a with N-bromosuccinimide at pH 4 (Scheme 3). Some of our previously published results on the degradation of dihydropalustrin (2a) are obviously at variance with the newly proposed structure for palustrin (1a). They can easily be explained by assuming a partial hydrogenolysis of the C(17)-N(1) bond during the preparation of dihydropalustrin from palustrin. Periodate cleavage of dihydropalustramic acid methyl ester (6b) liberates propionaldehyde, which can be trapped by working at pH 7.5 (Scheme 2); at lower pH values it condenses rapidly with the simultaneously generated 3,4,5,6-tetrahydropyridine derivative 15. The structure of the condensation product is proposed to be 16 on the basis of the isolation of its hydrogenation product, an isomeric dihydropalustramic acid (17).

Notizen: In order to investigate molecules and their interactions at interfaces we have developed a new spectroscopic technique based on integrated optics. A significant increase in sensitivity has been predicted and observed. We report here the details of the method and some preliminary spectra of organic dye molecules on thin films.

Notizen: Syntheses of jasmone (1), methyl jasmonate (3) and γ-jasmolactone (2) are reported, (Z)-nona-1, 6-dien-3-one (4) serving as common intermediate.

Notizen: The Conversion of Eperuic Acid into Ethers of the enantio-14, 15-Dinorlabdane Series5 and 6 are strongly odiferous substances of the ambra-type. Their enantiomers 7 and 8, hitherto unknown, have been synthesized from eperuic acid (4) and their olfactory properties compared with those of 5 and 6. 4 was esterified by CH2N2 and dehydrogenated with (C6H5Se)2/H2O2 to the α,β-unsaturated ester 9 (61%). Oxidation by KMnO4 in acetone yielded the ketone 3 (60%). Epoxidation followed by treatment with acid converted 3 into the acetals 7 (61%) and 8 (14%). 7 and 8 differ from 5 and 6 in odor intensity, and 6 and 8 show slightly different odor quality.

Notizen: Reduction Degree in Photoredox-SystemsThe reduction degree is in many photoredox systems an invariant under irradiation. Therefore it represents an important degree of freedom in these systems. It is possible to define the reduction degree in such a systematic way, that it may also be applied for discussing complicated systems. It would be helpful to have selective electrode material for the examination of photoredox systems. We have succeeded in finding a selective electrode material for the iron in the iron/thionin system as well as in the iron/iodine system.

Notizen: (E)-6, 10-Dimethyl-9-methylidene-undec-5-en-2-one (1) has been isolated from Costus root oil. A total synthesis of this compound is reported.

Notizen: The natural products methyl dehydrojasmonate (1) and tuberolactone (2) have been synthesized from methyl jasmonate (3) and jasmolactone (4) resp., via sulfenylation-sulfoxide pyrolysis.

Notizen: Comparative investigation of reactivities and ion structures upon electron impact induced degradations of the isomeric hydroxy cinnamic acid methyl estersBy analysis of energy release data in metastable peaks it is shown that m- and p-hydroxy cinnamic acid methylesters retain specific structural features upon degradation under electron impact, although their spectra are very similar and the shapes of the metastable peaks due to the initial methoxy cleavage are identical. A pronounced charge radical localization in the molecular ion is indicated. The o-isomer is found to yield a coumarin type structure by elimination of methanol, whose further degradation by decarbonylation involves at least three different mechanisms. The resulting ion structures are different from benzofuran.

Notizen: Eine Vielzahl photophysikalischer Prozesse kann theoretisch durch ein Dreiniveaux-Modell beschrieben werden. Die hier kritisch diskutierten exakten Lösungen der klassischen wie auch der quantenmechanischen Behandlung können im allgemeinen weit voneinander abweichen. Es ist gezeigt, weshalb einerseits die klassische Kinetik bei den bekannten Systemen bisher erfolgreich war und welche Eigenschaften andererseits nötig wären, um die Diskrepanzen merklich in Erscheinung treten zu lassen. Insbesondere lässt eine kurze Analyse der Zeitabhängigkeit neue interessante Effekte in der Pico-und Subpicosekundengegend erwarten.

Notizen: The Crystal Structure of a Bridged 1,2,3-Oxadiazolidin-5-one Derivative3-(2-Allylphenyl)-4-phenylsydnone (1) undergoes in solution an intramolecular, 1,3-dipolar cycloaddition reaction to give 2-oxo-1-phenyl-1,5-methano-1,2,4,5,6,11-hexahydro [1,2,3] oxadiazolo [3,2-a] cinnoline (2). The unique 1,2,3-oxadiazolidin-5-one structure of this molecule has been proved by X-ray analysis. The crystal structure has been solved by direct methods and refined by full-matrix least squares calculations to R = 0,046. The crystal system is orthorhombic, space group Pbca, with unit cell dimensions a = 10,546, b = 15,482, c = 16,531 Å.

Notizen: Rearrangements of the Phenylthio Group of Trimethylsilyl-enolethers of α,α-Dialkylated α-Phenylthio-ketonesTrimethylsilyl-enolethers of α,α-dialkylated α-phenylthio-ketones undergo a photochemically induced 1,3-phenylthio shift leading to isomeric enolethers in high yields. The rearrangement can also be carried out under thermal conditions, but the results are less satisfying.

Notizen: Detailed cation scavenger studies in pulse-irradiated pure, liquid CCl4 reveal that the 500 nm absorption has both, neutral and cationic characteristics, and that CCl4+ must be the precursor. It is shown that all experimental results are compatible with the following ion neutralisation mechanism: CCl3+ + Cl- → (CCl3+ · Cl-) → CCl4.The 500 nm band is assigned to the CCl3+-cation (free or complexed). Its neutralisation therefore does not occur on ion recombination, but is delayed by the life time of the ion pair: τ½ (ion pair) = 33 ± 3 ns at -22°C with activation energy of 10.9 ± 2.1 kJ/mol. Possible reasons for the ion pair stability are briefly discussed.

Notizen: Diazo-Group Transfer to Active Methylene Compounds Using Azidinium SaltsDie Synthese von Diazoverbindungen durch Diazogruppenübertragungen auf durch Carbonyl-, Cyan- und Nitro-Gruppen aktivierte Methylenverbindungen mit den Azidiniumsalzen 2-Azido-3-äthyl-benzthiazolium-tetrafluoroborat und 1-Äthyl-2-azido-pyridinium-tetrafluoroborat wird beschrieben.

Notizen: Diazo-Group Transfer to Hydroxy-arenes and Hydroxy-hetarenes Using Azidinium SaltsDie Einführung der Diazogruppe mit 1-Äthyl-2-azido-pyridinium-tetrafluoroborat und 2-Azido-3-äthyl-benzthiazolium-tetrafluoroborat in Hydroxybenzole, Hydroxynaphthaline und einige Hydroxy-hetarene wird beschrieben. Der Anwendungsbereich dieser Methode im Vergleich mit der Tosylazid-Methode wird diskutiert.

Notizen: Diazo-Group Transfer to Amino-arenes and Amino-hetarenes Using Azidinium Salts: Synthesis of 1, 2, 3-TriazolesDas Azidiniumsalz 2-Azido-3-äthyl-benzthiazolium-tetrafluoroborat (1) lässt sich als Diazogruppenüberträger auf Amino-arene und Amino-hetarene einsetzen. Die primär entstandenen Diazoniumsalze cyclisieren sich zu kondensierten ν-Triazolen bzw. kuppeln mit den Edukten zu o, o′-Diamino-azofarbstoffen.

Notizen: We have measured the stability constants of the cryptate complexes formed by ligands 1-4 with alkali, alkaline-earth, transition metal and toxic heavy metal cations. Stabilities and selectivities of complexation of the alkali and alkaline-earth cations are less pronounced in 1-4 than in the parent compounds 5 and 6 and decrease as the number of nitrogen sites increase. Remarkable complexation properties are found towards transition metal and toxic heavy metal cations. The intramolecular cavity of ligands 1-3 is too large for small cations like Co2+, Ni2+, Zn2+ so that the complexes formed are comparatively weak; however these cations are strongly complexed by ligand 4 whose intramolecular cavity has a much smaller size, compatible with their ionic radius. On the other hand, ligands 1-4 all form highly stable cryptates with Cd2+, Hg2+, Pb2+. Thus by the combined operation of the two structural parameters, cavity size and nature of the binding sites, cryptands 2 et 3 present very high selectivities for the complexation of these toxic heavy metal cations with respect to the biologically important ones Na+, K+, Mg2+, Ca2+, Zn2+. The selectivities of ligand 2 for Cd2+, Hg2+ and Pb2+ with respect to Zn2+ are as high as 106, 1018 and 109 respectively. They are much more pronounced than those of previously known complexing agents. Cryptands like 2 and 3 thus present a unique selectivity sequence of special interest in detoxication (decorporation, depollution). Further structural elaboration may allow to design ligands which present a given selectivity pattern of potential use in “cryptatotherapy” and “environment pollution control”. The results also provide evidence for the existence, at low pH, of protonated complexes which probably participate in an acid catalysed process for dissociation of the complexes.

Notizen: Synthesis of 4-amino- and 4-hydroxy-3-(p-chlorophenyl)-valeric acids. X-ray structure of cis-4-(p-bromophenyl)-5-methyl-2-pyrrolidinoneThe syntheses of diastereomeric 4-amino- and 4-hydroxy-3-(p-chlorophenyl)-valeric acids and of their ring closure products (lactones and lactams), starting from 3-(p-chlorophenyl)-4-oxo-valeric acid, are described. A single-crystal X-ray structure analysis of cis-4-(p-bromophenyl)-5-methyl-2-pyrrolidinone is given. Some aspects of the biochemistry of threo-3-(p-chlorophenyl)-4-amino-valeric acid are presented.

Notizen: Preparation of styryl derivatives of 2-phenyl-imidazo [1, 2-a]pyridine2-(p-Tolyl)-imidazo [1, 2-a]pyridines and 7-methyl-2-phenyl-imidazo [1,2-a]-pyridines can be converted, in dimethylformamide, on reaction with anils of aromatic aldehydes in the presence of potassium hydroxide or potassium t-butoxide, into the corresponding 2-(stilben-4-yl)- and 2-phenyl-7-styry1-imidazo [1, 2-a]-pyridines (‘Anil-Synthesis’). The 2-(p-tolyl)-imidazo [1,2-a]pyridines react far less readily than the 7-methyl-2-phenyl-imidazo[1,2-a]pyridines.

Notizen: Preparation of styryl derivatives of 2-phenyl-4H-1,2,4-triazolo [1,5-a]pyridine7-Methyl-2-phenyl- and 2-(3-chloro-4-methylphenyl)-4H-1,2,4-triazolo[1,5-a]-pyridines react with anils of aromatic aldehydes in the presence of dimethyl-formamide and potassium hydroxide at 20-45° to yield the 2-phenyl-7-styryl- and 2-(2-chloro-stilben-4-yl)-4H-1,2,4-triazolo [1,5-a]pyridines respectively (‘Anil Synthesis’). Further, the Schiff's bases derived from o-chloroaniline and 2-(p-formyl-phenyl)- and 7-formyl-2-phenyl-4H-1,2,4-triazolo [1,5-a]pyridine yield, with methyl- and with p-tolyl-substituted heterocycles, the corresponding heterocyclic substituted styryl and stilbenyl derivatives.

Notizen: The triplet-triplet absorption spectra of p-N, N-dimethylnitroaniline, 4-nitro-p-terphenyl, 1-amino-4-nitrofluorene, 5-nitroacenaphthene, trans-1-(4-methoxy-phenyl)-2-nitroethylene (MeONS), and trans-1-(4-dimethylaminophenyl)-2-nitroethylene (DANS) in EPA glass at 77 K are reported, together with molar extinction coefficients and PPP-SCF-MO-CI calculations. The two nitrostyrenes, MeONS and DANS, have been examined in fluid media at room temperature using nanosecond laser photolysis, and their triplet lifetimes found to increase substantially with increase in solvent polarity and charge-transfer character of the compound. This is interpreted in terms of the diradical/zwitterionic nature of the triplet state affecting the T1-S0 energy gap at the 90° twisted configuration of the olefinic linkage.The decrease in both the triplet yield and the fluorescence yield of DANS with increase in solvent polarity is explained by the intervention of an internal conversion process involving a rotation of the dimethylamino group in the lowest singlet excited state.

Notizen: The octahydroisoindolone moiety related to proxiphomin (1) has been synthesized by condensation of N-benzyloxycarbonyl-protected D, L-phenylalaninal (7) with methyl-(4-methyl-sorbyl)-malonate (11) to yield the branched ethylene derivative 12. Consecutive intramolecular [2+4]-cycloaddition and lactam ring closure of 12 gave the desired octahydroisoindolone derivative 15, possessing adaptable functional groups for the attachment of the macrocyclic ring system.

Notizen: Reaction Products from 3-Dimethylamino-2,2-dimethyl-2H-azirine and Phthalohydrazide or Maleohydrazide3-Dimethylamino-2, 2-dimethyl-2H-azirine (1) reacts in dimethylformamide at room temperature with the six-membered cyclic hydrazides 2, 3-dihydrophthalazin-1, 4-dione (2) and 1, 2-dihydropyridazin-3, 6-dione (15) to give the zwitterionic compounds 3 and 16, respectively (Scheme 1 and 7). The mechanism of these reactions is outlined in Scheme 1 for compound 3 (cf. also Scheme 8). The first steps are thought to be similar to the known reactions of 1 with the NH-acidic compounds saccharin and phthalimide (cf. [1]). Instead of ring expansion to the nine-membered heterocycle i (X=CONH, Scheme 8), a proton transfer followed by the loss of water gives 3 (Scheme 1).The structure of the zwitterionic compounds 3 and 16 is deduced from spectral data and the reactions of these compounds (see Schemes 2, 3, 4, 6 and 7). Methylation of 3 yields the iodide 4, which is hydrolysed easily to the 2-imidazolin-5-one derivative 5 (Scheme 2). Hydrolysis of 3 under basic conditions leads to the amide 6, which undergoes cyclization to 7 at 220-230° (Scheme 3). The analogous cyclization has been realized under acidic conditions in the case of 17 (Scheme 7).Catalytic reduction of 3 yields the tertiary amine 14 (Scheme 6), whereas the reduction with sodium borohydride leads to a mixture of 14 and the 2-imidazoline derivative 13. The alcohol 11, corresponding to the amine 14, is obtained by sodium borohydride reduction of the 2-imidazolin-5-one 7 or of the amide 6 (Scheme 3). This remarkably easy reaction of 7 shows the unusual electrophilicity of the lactamcarbonyl group in this compound. The reduction of 6 to 11 is understandable only by neighbouring group participation of N (2′) in the dihydrophthalazine residue.

Notizen: A calculation of the modification of the optical absorptions of an isotropic sample by a uniform external electric field is presented. The induced orientational anisotropy, the Stark shift and the field. dependence of the transition moment are taken into account up to the second order in the field. The final expressions differ in the contributions from the transition polarizabilities from previous results.

Notizen: The photoelectron spectrum of tris (methylidene)-cyclopropane 1 (“[3]radialene”) is reported and the electronic states of 1+ assigned. Jahn-teller activity in the degenerate states of 1+is discussed. Differences in the Franck-Condon profile of the first PE band and the Rydberg series in the Vacuum-UV./UV. absorption spectrum indicate for the Rydberg series (n=3) a 1A″2-species, which supports earlier tentative proposals. The high intensity absorption in the 5.5 eV-6 eV energy range of the latter spectrum recorded earlier are definitely due to impurities. The vibrational fine structure of a weak band system around 5.5 eV in our spectrum suggests for this transition S0→S2(1A′1), which is dipole forbidden but borrows intensity from S1(1E′) trough vibronic coupling via an e′-mode. From vapor pressure measurements ε(λmax=289 nm) = 9390± 1170 for gaseous 1 was found.

Notizen: IR. and Raman spectra of LnONO3 (50-4,000 cm-1, Ln=La, Gd, Eu, and Dy) are reported and discussed. The low frequency region of the spectra reflects the cubic structure of these compounds. The dimensions of the cubic unit cells determined by X-Ray powder diagrams are: 12.81 ± 0.05 Å for EuONO3, 12.69 ± 0.05 Å for GdONO3, and 12.67 ± 0.05 Å for DyONO3. The vibrational frequencies of the nitrato group are consistent with a bidentate nitrate of C2v symmetry. The synthesis of anhydrous Ln (NO3)3 (Ln=La, Gd, Eu, and Dy) by dehydration of the corresponding penta- or hexahydrates is described. The IR. and Raman spectra (50-4,000 cm-1) are analysed. Splitting of the bands point to a complex structure of these compounds. All six vibrational modes of the nitrato group are observed and the data are again consistent with bidentate NO-3 moieties. Finally, an analytical control of the purity of Ln (NO3)3 is suggested.

Notizen: As an extension of previous studies on the total synthesis of (2R,4′R,8′R)-α-tocopherol (1) [1] [2], (S)-(-)-2-(6-benzyloxy-2,5,7,8-tetramethylchroman)acetic acid (6), a pivotal intermediate, possessing the absolute configuration required for construction of 1 was prepared by optical resolution of the racemic modification 11. the latter substance was obtained by two routes, one emanating from the hydroxy acetal 7 [1] and the other based upon the Lewis acid mediated cycloaddition of trimethylhydroquinone to rac.-3-hydroxy-3-methylpent-4-en-l-yl acetate (16) giving rac. ethyl 2-(6-hydroxy-2,5,7,8-tetramethyl-chroman)acetate (12).

Notizen: Thermodynamic study of charge transfert complexes (n-σ*) in solutionCharge transfer complexes of quinoline and substituted quinolines (donors) with iodine, iodine chloride, and iodine bromide (acceptors) have been studied spectrophotometrically in CCl4. The 1:1 stoechiometry of these complexes was verified by means of the continous variations method and the appearance of isosbestic points. Simultaneous determination of the equilibrium constant and enthalpy of adduct formation was carried out by calorimetry.It was observed for every donor that the equilibrium constants of the complexes studied increase with the strength of the acceptors. A linear correlation between enthalpy of adduct formation and donor strength was obtained only for the complexes Donor ICI.

Notizen: Conditions and implications for the calculation of self-consistent single determinant wave functions for Koopmans' ions are discussed and a recipe for practical computations is given. The concept of Koopmans' ions has been extended to localized ions and a definition for their reorganization energies is proposed. Calculations on formaldehyde serve as a numerical illustration.

Notizen: Upon flash pyrolysis between 580 to 660°, 2,4,6-tris(chloromethyl)mesitylene (2) leads to products formed through the loss of one, two and three molecules of HCl. The highly reactive chlorine free product is shown to be [6]radialene (1) both by its chemical reactions and by its spectral properties.

Notizen: Structure and Reactivity of a Triazolo-benzodiazepine/Oxalyl Chloride AdductReaction of oxalyl chloride with N, N-dimethyl-{8-chloro-6-(0-fluorophenyl)- 4H, 11 H-[1,2,4]triazolo [1,5-α] [1,4]benzodiazepine}-2-carboxamide (6a), the syn-thesis of which is described, leads to the cyclic adduct N, N-dimethyl-{2,12,12-trichloro-13a-(0-fluorophenyl)-11-oxo-10,11,12,13a-tetrahydro-5H, 9H-[1,3]oxazolo [3,2-d] [1,2,4]triazolo [1,5-a] [1,4]benzodiazepine}-7-carboxamide (7a). Upon thermolysis 7a is partly reconverted to the starting diazepine 6a via loss of the elements of oxalyl chloride. Reduction of 7a with sodium borohydride also yields 6ain addition to its dihydro derivative 9. Energetic treatment of 7a with sodium methoxide leads to the unexpected methoxydiazepines 10a and 10b, and mild treatment of 7a with sodium methoxide to the stereoselective formation of the two precursors of 10, namely the chloromethoxy derivative 11 and the dimethoxy derivative 12. Epimerization of 11 followed by nucleophilic substitution gives a mixture of two dimethoxy compounds, 12 and its epimer 14. The configurational assignments of these derivatives are based upon X-ray analysis of 12. A possible pathway for this unexpected substitution reaction is proposed.

Notizen: Synthesis of 4-[3β, 14-Dihydroxy-5β, 14β-androstan-17β-yl]-3-pyrrolin-2-one (hothesimogenin)We describe the synthesis of 4-[3β, 14-Dihydroxy-5β, 14β-androstan-17β-yl]-3-pyrrolin-2-one (24-aza-24-desoxa-digitoxigenin) (7), starting from 3-O-acetyl-digitoxigenin (1).

Notizen: The 2-cyclohexene-imines 2b-2d and the hexahydroquinolines 5a, b are synthesized. n,π*-Excitation of these α,β-unsaturated imines leads to (E/Z) isomerization for compounds 2 while compounds 5 are unreactive. No cyclobutanes are formed from 2 or 5 under these conditions in the presence of olefins, and only 2d adds to 2,3-dimethyl-2-butene via the C=N bond to give an azetidine. On π,π* excitation 2 and 5 rearrange to the corresponding β,γ-unsaturated imines 8 and 9 with low efficiency. It is concluded that the failure of such imines to undergo [2+2]-photocycloadditions with olefins is not mainly due to radiationless decay via (E/Z) isomerization.

Notizen: Transamidation Reaction of Open Chaine Amino-amidesAmino-amides of type 11 with a primary amino and a N, N-disubstituted amide group isomerize under base catalysis completely to amino-amides 16 with a secondary amino and a N-monosubstituted amide group (see Scheme 3). Amino-amides having a secondary instead of the primary amino group are under base catalysis in equilibrium with the corresponding isomeres (Scheme 4). The opening of the proposed tetrahedral intermediate 13 (Scheme 3) takes place under stereo-electronic control (Schemes 5 and 6).

Notizen: Diazo coupling of 3,4-dimethoxyfuran with aryl diazonium ions3,4-Dimethoxyfuran (1) easily reacts with aryl diazonium chloride in aqueous pyridine in an expected 1, 4-addition reaction. From the isolable primary addition product pyridine is displaced by alcohols, phenols or thiols to yield 4-alkoxy- or 4-phenoxy- or 4-thiophenoxy-derivatives of 2,3-dimethoxy-2-buten-4-olide (3). Attempts to convert them into azo compounds by a base catalysed 1, 6-elimination reaction failed. Oxidation of 3a and 3c with DDQ results in the formation of the mono p-nitrophenylhydrazone of 3, 4-dimethoxymaleic acid anhydride. On the other hand, the thiophenoxy compound 3g is smoothly converted by MnO2 into the authentic furan-2-azobenzene derivative 5.

Notizen: Transamidation Reactions with Cyclic Amino-amidesLactames which are substituted at the nitrogen atom by a 3-aminopropyl residue are transformed under base catalysis to cyclic amino-amides enlarged by 4 ring atoms. The formed ring must be at minimum 12-membered. Scheme 2 illustrates this result: the 8-membered 7 is transamidated in 96% yield to the 12-membered ring 8 (in the presence of potassium 3-aminopropylamid in 1, 3-propanediamine), the 9-membered 10 to the 13-membered ring 11 (97%) and the 11-membered 14 to the 15-membered ring 15. Furthermore, the 13-membered ring 27 (Scheme 5) is transformed to the 17-membered 28. In the case of the 15-membered lactame 15 it is demonstrated that 14 is not formed back under the conditions of the transamidation.Large ring lactames which are substituted at the nitrogen atom by a 3-(alkylamino) propyl group lead under base catalysis to an equilibrium mixture, e.g. the 17-membered 26 is in equilibrium with the 21-membered 29. This result is similar to the behavior of the corresponding open-chain amino-amides [2].Because of transannular interactions, the 11-membered ring 2 is not stable: transamidation of the 7-membered 1 (Scheme 1) doesn't give the expected 2, but its water elimination product 3 in small yield. The N-tosyl derivative of 2, namely 20, is synthesized by an independent route (Scheme 3). Detosylation of 20 yields the 7-membered 1 instead of 2. Concerning the mechanism of this interesting reaction see Scheme 4.

Notizen: Les spectres IR. de cinq spiropyrannes benzothiazoliniques (ét solide et dissous) et les spectres Raman de trois d'entre eux (état solide) ont été enregistrés de 4000 à 400 cm-1 et ont permis une interprétation des vibrations moléculaires de ces composés. Une analyse plus sommaire, faite dans le but de caractériser la structure spiropyrannique a été étendue au moyen de la spectroscopie IR. à une série de vingt et un composés. L'étude IR. a également porté sur deux mérocyanines. Nous avons analysé et essayé d'interpréter les principales perturbations spectrales observées lors du passage d'un composé spiropyrannique (forme fermée) à la forme ouverte.

Notizen: The photoelectron spectrum of tetrakis (methylidene)cyclobutane (1, ‘[4]radialene’) is reported. The electronic states of 1+ are assigned on the basis of model calculations and with reference to related systems. Jahn-Teller activity in the degenerate states is discussed. A failure of the simple LCBO-model for the π(eg)-orbital of 1 is noted and traced to the fact that this orbital, though having a symmetry-equivalent π*-counterpart, does not interact with it. This feature is confined to [4n]radialenes; their total π-energies are therefore higher than those of the other members. It is shown that radialenes, in principle, do not constitute a class analogous to that of the linear polyenes as inferred earlier.

Notizen: The He(Iα) and He(IIα) spectra of tetrafluorobutatriene 3(F) have been recorded for comparison with those of butatriene 3(H). Ab initio double-zeta basis self-consistent field (SCF) and configuration interaction calculations on butatriene show that, contrary to previous assignment, no shake-up band is expected to appear in the 9-10 eV energy range of the photoelectron spectrum. Further, such SCF calculations on tetrafluorobutatriene support the use of the perfluoro effect in assigning the purely π orbital ionizations. It is argued that 3(F) is a key compound for the study of the perfluoro effect. This is supported by a qualitative comparison of its photoelectron-spectroscopic results with those of other perfluoro systems.

Notizen: Stationary points of the INDO energy hypersurface for various orientations of ethylene in external electric fields of the strength F=0, 2, 4, 6, 8 and 10 × 1010 V m-1 were found and their characteristics studied by the force constant matrix analysis. Energies, structural parameters, charges, Wiberg indices and dipole moments are presented. The only stable orientation of the ethylene molecule is that for which the C—C bond is parallel to the field direction up to F=6 × 1010 V m-1 (orientation (a) in Fig. 1). Above this value the molecule is structurally unstable and it decomposes to the hydride anion and the C2H3+ cation. Rotational instability was found for two perpendicular orientations of the C—C bond with respect to the field vector, in which the field vector was parallel and perpendicular to the molecular plane. Pseudorotations with negative eigenvalues of force constant matrices lead to the stable orientation (a). No stationary points were found when the angle between the C—C bond and the field vector was between 0 and 90°. The five longest wavelength vibrational bands are presented for selected orientations and field strengths.

Notizen: Delayed fluorescence (DF.) spectra of 1,2-benzanthracene, fluoranthene, pyrene, and chrysene in methylcyclohexane were measured at -80° up to the wavenumber corresponding to the energy of two triplets. With all four compounds a weak DF. Sn → S0 from the highest state Sn accessible by triplet-triplet annihilation (TTA) was found. Lifetimes of Sn calculated (a) from the ratio of the DF's Sn → S0 and S1 → S0 and (b) from the difference in line-width of the 0,0-transitions Sn,0 ← S0,0 and S1,0 ← S0,0 agree reasonably well. This indicates that population of the highest accessible excited singlet state is the dominating primary process in the excited singlet channel of TTA. There is no evidence for excimer formation being the first step in TTA. DF. spectra extend up to the energy of two triplets. With pyrene the intensity distribution in the hot-band region of the DF. S2 → S0 suggests that in TTA the same vibrational selection rules are valid as in one-photon absorption S2 ← S0 and that vibrational relaxation within the S2 manifold is slow compared with internal conversion S2 ↝ S1. The experimental technique is described in detail and experimental difficulties arising from impurities and photoproduct formation are discussed.

Notizen: During UV.-irradiation of aliphatic carboxylic acids and esters in aqueous and nonaqueous solutions various alkyl and acyl type radicals derived from parent compounds and solvents have been observed by ESR.-spectroscopy. The structures of the radicals point to α-cleavage, β-dehalogenation and photoreduction as major photolytic processes of carboxylic acids and esters. The relative contributions of these processes to the overall photodecompositions depend on the carboxyl substituents, on solvent and temperature. Similarities of carboxyl and carbonyl group photochemistry are discussed.

Notizen: The Synthesis of Actinioerythrol, Violerythrin and other 2,2′-Dinor-carotenoids2,2′-Dinor-carotenoids including the naturally occurring actinioerythrol (1) and the blue carotenoid violerythrin (2), as well as 2,2′-dinor-rhodoxanthin (25) and 2,2′-dinor-zeaxanthin (27) and others have been obtained by total synthesis.

Notizen: On the Mechanism of Radiationless Deactivation of the First Excited Singlet State of 2-Alkyl-indazolesThe temperature dependence of the quantum yields of fluorescence (ΦF), intersystem crossing (ΦT) and photoreactions (ΦR) have been measured for several neutral and protonated 2-alkyl-indazoles. The experimental data (Fig. 1 and 3) can be interpreted in terms of the reaction schemes 1 and 2 with temperature independent constants for fluorescence emission and intersystem crossing and temperature dependent photochemical primary processes. Whereas at low temperatures the sum of the quantum yields of fluorescence and intersystem crossing equals 1, at higher temperatures a very efficient radiationless deactivation process takes place (Table). Based on kinetic and photochemical data it is concluded that this deactivation proceeds via a hypersurface crossing (Fig. 2) or hypersurface touching (Fig. 4) in the course of the photochemical rearrangements 1 → 2 and 4 → 5 respectively.Similar mechanisms are expected to be responsible for the unusual internal conversion in other heterocyclic compounds.

Notizen: Using the Frozen Core (FC) MO procedure described in a previous communication, we have computed the long-wavelength chiroptic properties of oligopeptides in the parallel-chain (PC) pleated sheet conformation, in the poly (L-proline) I and poly (L-proline) II conformations. The main features of the computed results are: (a) In the PC pleated sheet conformation the π-π* transition with the highest positive rotatory strength appears at shorter wavelength than the π-π* transition with highest negative rotatory strength and is polarized mainly perpendicularly to the chain axis. There is an analogy between the computed PC pleated sheet spectrum and that calculated for a cyclohexapeptide of low symmetry, in a conformation which is probably stabilized by intra-annular hydrogen bonds. (b) In the polyproline I conformation the computed π-π* transition with highest positive rotatory strength is also the longest-wavelength π-π* transition and is polarized mainly along the helix axis. There is an analogy between this spectrum and that calculated for cyclo(tri-L-proline) of symmetry C3. (c) The poly-proline II CD. spectrum may be qualitatively reproduced only by invoking very strong n - π interaction. The local n -π mixing parameter Λ must take on values ⋝3 eV, which is of the order of a nearest-neighbor core resonance integral between atomic 2p orbitals of same spatial orientation. The question concerning the structural reasons for this situation is raised. As far as comparisons with experimental data are possible, qualitative agreement is obtained.

Notizen: 5,6-Dimethylidene-exo-2,3-epoxynorbornane (1) is reduced slowly by LiAlH4 in boiling tetrahydrofuran (THF) and furnishes a mixture of 5,6-dimethylidene-exo-2-norbornanol (2), 2,3-dimethylidene-anti-7-norbornanol (3) and principally 6-methyl-5-methylidene-anti-3-nortricyclanol (4). The yield of 4 is the highest for low initial concentrations of LiAlH4; it decreases in favour of alcohols 2 and 3 at high concentration of LiAlH4. The reduction of 1 with AlH3 in THF yields 3 as the major product, thus revealing an efficient synthesis of 7-substituted-2, 3-dimethyl-idenenorbornane derivatives. No alcohol 2could be isolated by LiEt3BH reduction of 1. LiAlD4 reduces 1 into the monodeuterated alcohols 2-d, 3-d and 4-d. The deuterium label is found in the endo-position at C (3) in 2-d, in the exo-position at C(5) in 3-d and in the methyl group of the tricyclic alcohol 4-d. Mechanistic limits for the formation of 2, 3 and 4 are discussed briefly.

Notizen: The enthalpy of formation of tris(methylidene)-cyclopropane (“[3]radialene”, 1) has been determined as ΔHfO = 396 ± 12 kJ mol-1 from three fragmentation reactions of its molecular ion 1+ formed from 1 by photoionisation using synchrotron radiation. Comparative electron impact measurements using conventional mass spectrometry were also performed. A treatment of the latter data is described which leads to satisfactory agreement with the photoionization data. The experimental value of ΔHfO(1) is compared with various theoretical estimates. The strain energy of 1 is calculated to be 226.3 kJ mol-1. Linear extrapolation of this quantity from the increase of strain in passing from cyclopropane to methylidenecyclopropane yields 282.4 kJ mol-1. The discrepancy between these values, already predicted by Dewar and Baird ten years ago from theoretical calculations, is discussed on the basis of maximum overlap considerations. The enthalpy of formation of bis(methylidene)cyclopropane is predicted to be ΔHfO= 309 kJ mol-1.

Notizen: Leaf-gland Pigments: 6-Novel p-Quinomethanes of the Abietane Series from Plectranthus parviflorus WILLDThe above mentioned plant accumulates in its red coloured leaf-glands a complex mixture of strongly dehydrogenated abietanols. They were separated (with difficulties) to yield 6 novel compounds. Spectroscopic and chiroptic data show them to be esters of either 11, 19-dihydroxy- or 2 α, 11-dihydroxy-abieta-5, 7, 9 (11), 13-tetraen-12-one 2a and 3a, respectively. Specifically, the 19-O-p-hydroxybenzoate (2d) parvifloron C, the 19-O-vanilloate (2c) parvifloron B, the 19-O-p-hydroxy-benzoate (2d) parvifloron C, the 19-O-3′,4′-dihydroxybenzoate (2e) parvifloron E, the 2 α-O-p-hydroxybenzoate (3b) parvifloron D, and the 2 α-O-3′,4′-dihydroxy-benzoate (3c) parvifloron F. Reduction by LiAlH4 splits the ester function and reduces the p-quinomethane to a colourless pyrocatechol derivative which, by air oxidation, regenerates the red p-quinomethane system of 2a and 3a.

Notizen: Synthesis of 3-Dimethylamino-3a,4,5, 7a-tetrahydro-1H-isoindol-1-ones by Intramolecular Diels-Alder ReactionThermolysis of N2-acylamidines, the acyl group of which derives from an α,β,γ,δ-unsaturated carboxylic acid (2, 5-7), yields 3-dimethylamino-3a,4,5,7a-tetrahydro-1H-isoindol-1-ones (3,8-10, Schemes 1 and 3) in 63-78%. Only the thermodynamically controlled cis-fused ring system is formed. The starting materials are readily available by the reaction of 3-dimethylamino2H-azirines (1 and 4) and carboxylic acid chlorides.

Notizen: Reactions of Aziridino-nitrenes: Synthesis of Polycyclic Bisaziridines and 1,2-Bisaziridino-diazenesVorgetragen in der Versammlung der Schweizerischen Chemischen Gesellschaft in Bern am 7.Oktober 1977.7-Amino-7-azabicyclo[4.1.0]-3-heptene (11b), cis-9-amino-9-azabicyclo[6.1.0]-nonane (12b), cis-9-amino-9-azabicyclo[6.1.0]-(4Z)-nonene (13b), as well as exo- and endo-3-amino-3-azatricyclo[3.2.1.02,4]-6-octene (14b and 15b) were synthesized by addition of oxidatively generated phthalimido-nitrene (6) to 1,4-hexadiene, (Z)-cyclooctene, (1Z,5Z)-cyclooctadiene, and bicyclo[2.2.1]heptadiene, respectively, followed by hydrazinolysis of the corresponding N-phthalimido-aziridines 11a-15a.Lead tetraacetate oxidation of the two unsaturated N-amino-aziridines 11b and 15b at -70° yielded diazapolycyclic structures by intramolecular addition of the intermediate aziridino-nitrenes 11c and 15c to the δ, ε-situated C, C-double bond; the products obtained in good yields were 1,5-diazatetracyclo [3.3.0.02,8. O4,6]-octane (16) and 3,7-diazapentacyclo [3.3.1.02,4.03,7.06.8] nonane (17), respectively Oxydation of the unsaturated N-amino-aziridine 13b under the same conditions did not cause intramolecular addition of the nitrene 13c to the ε, ζ-situated C, C-double bond; instead 1,2-bis (cis-9-azabicyclo [6.1.0]-(4Z)-nonen-9-yl)-diazene (20) was obtained in low yield and (1Z, 5Z)-cyclooctadiene as the main product. Both products can be rationalized as derived from the intermediate nitrene 13c with 13b and the olefine as the result of a fragmentation of 13c under extrusion of N2. As. expected, oxidation of the saturated N-amino-aziridine 12b led to the 1,2-bisaziridino-diazene 21 and (Z)-cyclooctene in a ratio of 4:6. Surprisingly, oxidation of 7-amino-7-azabicyclo [4.1.0]-heptane (10b) produced only fragmentation of the corresponding nitrene 10c to cyclohexene. Finally, oxidation of the exo-N-amino-aziridine 14b yielded a complex not yet resolved product mixture in low overall yield. Attempts to add the oxidatively generated aziridino-nitrene 12c to cyclohexene, methyl acrylate, and dimethylsulfoxide were without success.Heating the 1,2-bisaziridino-diazenes 20 and 21 at their respective m.p. temperatures caused thermal fragmentation to occur with evolution of nitrogen. The bisaziridines 26 and 28 as well as the aziridines 27 and 29, respectively, were isolated. These products could be the result of a radical pathway, whereas a small amount of (Z)-cyclooctene, also generated in the thermolysis of 21, might be formed by a competing cheletropic pathway.The 1H-NMR-spectra of the derivatives of cis-9-azabicyclo[6.1.0]nonane, namely of 12a, 12b, 21, 28 and 29, showed signals for some of the aliphatic protons which were separated from the others at relatively low field (around 2.5-1.8 ppm). These signals accounted for 4 (with 12b for 2) protons in each of the cis-9-azabicyclo[6.1.0]nonane subunits, i.e. more than the 2 expected for the aziridine methine protons. The additional signals must be assigned to methylene protons (2 or even 4 of them) probably situated on the other side of the eight membered ring and deshielded by the motion-average proximity to the aziridine nitrogen atom.

Notizen: On the Carotenoids Flavoxanthin and Chrysanthemaxanthin: 1H-NMR., 13C-NMR. and Mass Spectra, Absolute Configuration, Survey of Published DataVery pure flavoxanthin (1) and chrysanthemaxanthin (2) have been reisolated from flower heads of Taraxacum officinale. Both compounds were characterized by chromatographic, chemical and chiroptical data and extensive NMR. measurements. Examination of many published data on 1 and 2 led to the conclusion that flavoxanthin has often been mistaken for chrysanthemaxanthin and vice versa.Chemical degradation of 1 and 2 to (-)-loliolide (5) coupled with NMR. evidence (ASIS, spin-decoupling, NOE) allowed the assignment of the absolute configurations of 1 and 2. Thus (+)-flavoxanthin is (3S,5R,8R, 3′R,6′R)-5, 8-epoxy-5, 8-dihydro-β, ε-carotene-3, 3′-diol and (+)-chrysanthemaxanthin its C(8)-epimer.

Notizen: Synthesis and Chirality of (5S,6R)-5,6-Epoxy-5,6-dihydro-β,β-carotene and (5R,6R)-5,6-Dihydro-β,β-carotene-5,6-diol, a Compound with Unexpected Solubility CharacteristicsWittig-condensation of azafrinal (1e) with the phosphorane derived from 7 leads to a (1:3)-mixture of (E)-9′- and (Z)-9′-β,β-carotene-diol 3, from which pure and optically active 3 ((5R,6R)-5,6-dihydro-β,β-carotene-5,6-diol) has been isolated as bright violet leaflets, m.p. 168°. Due to the trans-configuration of the diol moiety and to severe steric hindrance, hydrogen bonding is reduced to such an extent, that 3 behaves much more as a hydrocarbon than as a diol. There is good evidence that the so-called ‘β-oxycarotin’ obtained by Kuhn & Brockmann [15] by chromic acid oxidation of β, β-carotene is the corresponding racemic cis-diol. 3 has been converted into (5S, 6R)-5,6-epoxy-5.6-dihydro-β,β-carotene (4), m.p. 156°. This transformation establishes for the first time the chirality of a caroteneepoxide (without other O-functions).Full spectral and chiroptical data including a complete assignement of 13C-chemical shifts for azafrin methyl ester and 3 are presented.

Notizen: Leaf-gland pigments from labiatae: structures of 16 diterpenoids (coleons and royleanones) from Coleus coerulescens GÜRKEThe Abyssinian labiate Coleus coerulescens has been investigated for its leaf-gland pigments. From the very complex mixture of abietanoic diterpenoids the following pure constituents were isolated and their structures established: (1)Diosphenols: coleon C (1a), 16-O-acetyl-coleon C (1b), coleon W (1f);(2)A/B-trans-6, 7-diketones: coleon D (2b), 16-O-acetyl-coleon D (2c), coleon V (2a);(3)Spiro-coleons: 7,12-bis(O-desacetyl)-coleon N(3a), 12-O-desacetyl-coleon N (3b), coleon O (4), 6,12-bis (O-desacetyl)-coleon R (5a), 12-O-desacetyl-coleon R (5b), 3-O-desacetyl-3-O-formyl-coleon Y (5g);(4)Royleanones: The abeo-compounds 6a, 6b, and 7.Main compounds are 3b, 5e and 5g. This is the first record of a co-occurrence of diosphenols, 6,7-dioxo-coleons, spiro-coleons and royleanones. Preliminary experiments show that solvolytic opening of the cyclopropane-ring followed by tautomerisation, oxidation to hydroxy-p-benzoquinones or elimination to quinomethanes and subsequent nucleophilic attack of the solvent leads to compounds with a 2′-substituted propyl group at C(13), thus supporting the biosynthesis of the unusual coleon E side chain.

Notizen: Thirty-three 1-β-D-pentofuranosylcytosine nucleosides were examined as substrates of crude cytidine deaminase from mouse kidney. In addition to previous observations of structural features in substrates required for enzymatic deamination [e.g., a free 3′-hydroxyl in the ‘down’ ribo (arabino)configuration] we find that: modification of the aglycon by substitution of a fluorine atom at C(5) results in a several-fold increase in the deamination velocity relative to cytidine whereas insertion of a methyl group at C(5) decreases the deamination velocity. This decrease is even more pronounced when a methyl group is substituted at C(6).Though xylosylcytosine and 3′-deoxy-3′-fluoro-xylo-C are not substrates for this deaminase, those xylofuranosylcytosines bearing good leaving groups (e.g., bromo, mesyloxy, or tosyloxy) at C(3′) are deaminated with substantial deamination velocities. This is probably due to a prior chemical reaction leading to arabino nucleosides bearing a free ‘down’ 3′-hydroxyl.A different situation is obtained with arabino nucleosides. Though ara-C and 2′-deoxy-2′-fluoro-ara-C are substrates for this deaminase, substitution of bulky groups (e.g., chloro, bromo, or mesyloxy) at C(2′) substantially decreases the susceptibility to deamination. An hypothesis is offered to explain these differences between xylo-and arabino-cytosines.The presence of a free hydroxyl group at position 5′ is not essential for enzymatic deamination.

Notizen: 2-Thiopyridone (2-mercaptopyridine, 1) was found to be a very suitable reagent for removing the Nα-o-nitrophenylsulfenyl (NPS-) group in both conventional and solid-support peptide synthesis. A 3- to 5-molar excess of the reagent together with an equivalent amount of glacial acetic acid in methanol, dimethylformamide, or methylene chloride produces the soluble, stable mixed disulfide, 2-nitrophenyl 2-pyridyl disulfide (2), and the Nα-deprotected amino-acid or peptide. The yields are quantitative in less than 5 min if all educts are dissolved, in about 20 to 30 min in solid-support synthesis. No modifications of either the indole side-chain of tryptophan or of a series of side-chain protecting groups, in particular of the t-butyl type, are produced. No adverse side-reactions (insoluble disulfides) were observed. The procedure is illustrated with a series of amino-acid derivatives and with the solid-support synthesis of [5-leucine]-enkephalin.

Notizen: The two novel tricyclic C10H16 compounds anti- and syn-tricyclo [4.2.1.12,5]- decane (16 and 17, respectively) were synthesized starting either from the photodimer 2 (anti) or the two cycloaddition products 8 (anti) and 9 (syn).

Notizen: The title condensations gave respectively: gem-bisarylated cyclic amines 3a-k or monoarylated unsaturated cyclic amines 4a-g, 1,3-bisarylated cyclohexadienes 6a, 6b, the condensed bicyclo [2,2,2]-octane 8. In addition the aromatic ketone 9 gave the fluorenone 10 on treatment with polyphosphoric acid (PPA).

Notizen: Nickel-catalysed Synthesis of α-NornicotinesSchiff's bases 1 and butadiene generally co-oligomerize on nickel catalysts to yield octatrienyl-substituted amines 2 and octadienyl-substituted imines 3.Schiff's bases 4 and 5, on the other hand, react with 1, 3-dienes to give new [3+2]-cycloadducts 6. In addition to the appropriately functionalized α-nornicotine derivatives some higher oligomers are formed.

Notizen: Chemical Synthesis of the Nonanucleosideoctaphosphate dA-T-G-A-T-G-A-A-AFor studies on the specifity of enzymes, the nonanucleoside octaphosphate dA—T—G—A—T—G—A—A—A was required. Its chemical synthesis is reported starting with the monomers dA, dpT, dpG and dpA.

Notizen: The complexation of La3+, Ce3+, Pr3+ and Sm3+ ions with isopropylmercaptan has been studied by potentiometric and conductometric titration techniques in aqueous - 10% ethanolic (V/V) medium. Title metal ions form 1:1, 1:2 and 1:3 complexes in the pH range 6.0-8.0 with considerable overlapping. Their log Kstab. values are determined at 15°, 25° and 35°C at ionic strength μ = 0.1 M (NaClO4) by applying Calvin and Melchior's extension of Bjerrum method. The values of thermodynamic parameters ΔG, ΔH and ΔS have been calculated at 25°C with the help of an isobar and Gibb's Helmholtz equation. The trend in the stability constant values of the metal-complexes has been found to be \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm Sm}\left({{\rm III}} \right) 〉 {\rm Pr}\left({{\rm III}} \right) 〉 {\rm Ce}\left({{\rm III}} \right) 〉 {\rm La}\left({{\rm III}} \right) $$\end{document}.

Notizen: Sydnone Ethylenes. III. Chemical Reactions of Excited 4-Styryl-sydnonesDependent on the character of the substituents in the photo reactions of 4-styryl sydnones Z/E-isomerism competes with CO2-elimination. Excited p-nitrostyryl sydnones exhibit a relatively strong degradation of the bond order in the C—C region. Their quantum yields of Z/E-isomerism are therefore much higher than those of compounds with p-substituents of lower acceptor effect. In these compounds the cleavage of the sydnone ring with elimination of carbon dioxide is favoured especially if a methyl group is in 3-position of the sydnone.

Notizen: Reactivity and Toxicity of Homologous Bromo- and DibromoalkanesThe rate constants of the reactions of 4-(4-nitrobenzyl)-pyridine (NBP) with ω,ω′-dibromoalkanes Br—(CH2)n—Br (n = 2-4), alkyl bromides CnH2+n1Br (N = 2-4) and allyl bromide in acetophenone were measured and compared with the LD50-values of these compounds estimated on mice. The tested dibromoalkanes show a contrary graduation of reactivity and acute toxicity.

Notizen: Kinetische Studien über nucleophile Substitutionsreaktionen von α- und β- Naphthacylbromiden mit Natriumbenzoat in wäßrigem Äthanol

Notizen: Synthesis and Photochemistry of Sydnonazomethines-(4)Sydnon-4-aldehydes 1-3 react with prim. amines or N-sulfinylanilines to sydnon-azomethines. The i.r.-spectra are discussed. Sydnonazomethines undergo a photoinduced E/Z-isomerisation, at room temperature; a rapid thermic back-reaction (Z/E-isomerisation) takes place, however. The photostationary states at -75°C are analyzed. The rate constants of the thermic back-reaction at 18°C are measured by means of flash-photolysis. The quantum yields for the E/Z-isomerisation (at -75°C) and the photolytic decomposition have the value of 〉0,1 and 〈10-3 respectivly.

Notizen: On the Preparation of Isocyanatoderivatives of Aliphatic DiethersA method for the preparation of some isocyanates of aliphatic diethers of the general formula: CH3(NCO)—O—[CH2]n—O—CH(NCO)CH32a-e, where n = 1-5 has been reported. The syntheses conditions, properties, as well as the conversion of the obtained diisocyanates into the new urea derivatives were described.

Notizen: A Simple Calculation Method for the Estimation of the Inductive Effect of Different SubstituentsA new method without great mathematical operations for the estimation of the inductive effect of any substituents is described. The starting values are the electronegativities and the bond lengths of the atoms of the corresponding substituent.The ID values, received by this method show a good correlation with the known electronic parameters (F, σ′, σ*, σI and σqI) and with the velocity constants and equilibrium constants of chemical reactions, respectively.

Notizen: d-N.M.R.-Investigation of the Restricted Rotation at the -Bonding Increment. X. N-Substituted Thiocarbamic acid-O-Phenyl- and S-EthylestersThe free enthalpies of activation of the restricted rotation at the partial -double bond in thiocarbamic acid esters have been determined for (R1 = methallyl; R2 = me, et, iso-pr, cycl. hex; X = S and Y = O—C6H5 respectively X = O and Y = S—C2H5). The results have been compared with values, earlier observed for other mono- and dithiocarbamic acid esters, substituted at nitrogen analogously.

Notizen: Reactions of Alkenes in the Presence of Tungsten- and Molybdenum-containing Ziegler-Natta-CatalystsIn connection with investigations of reactions of alkenes under the conditions of metathesis we studied the reactions of a mixture of 2-pentene/toluene in presence of the catalytic systems WCl6/EtAlCl2 and MoCl5/EtAlCl2 in homogeneous liquid phase.Alkylation of toluene, metathesis of 2-pentene and also indirect isomerisation of double bonds have been determined in dependence of the molar proportions of 2-pentene/MeClx, toluene/2-pentene, and MeClx/EtAlCl2, the addition order (“formation”) of reactants, the “building time” of catalytic system and the reaction time.Compositions of the reaction mixtures have been determined by GLC.

Notizen: Synthesis of Nitro- and Amino-Substituted Thiobenzamides by Thiolation Reactions with Elemental Sulfur at Mild ConditionsThe Synthesis of thiobenzamides 2-7 by basecatalyzed thiolation of nitro-benzyl-halides (type 1), especially at low temperatures, and the selective synthesis of p- and m-nitro-thio-benzamides (2, 3) or p-and m-amino-thiobenzamides (5, 6), respectively, are described. o-Nitro-benzylhalides (→ 4, 7) are less reactive than p- and m-nitro-benzylhalides.The reaction of nitrobenzylhalides (type 1) with elemental sulfur and amines occuring at low temperatures to give 2-4 leads via structures of the type 11, 15 and 16.

Notizen: 13C-N. M. R. Chemical Shifts of Aromatic Sulfonamides

Notizen: MO-LCAO Calculations on Polymethines. IX. On the Chromaticity of Coupled Oxonol and Cyanine DyesStreptopolymethines display low-energy electronic transitions with a high transition probability and possess, moreover, a high capability to accept or to release electrons. These properties account for the absorption colour of polymethine dyes consisting of two molecular fragments. Scope and limitations of a composite-molecule approach can be recognized by subjecting the electronic wavefunctions to the so-called configuration analysis. Colour-structure relationships are derived from inspection of key orbital interactions between the molecular fragments.

Notizen: α-Substituted Phosphonates. XXXI. The Reaction of N,N,N′,N′-Tetramethyl Chloroformamidinium Chloride with P(III) CompoundsN,N,N′,N′-Tetramethyl chloroformamidiniumchloride (4) does not react with triethyl phosphite (TEP) or isopropyl diphenylphosphinate to give the expected bisphosphoryl derivatives 7 and 11, respectively, but primarily the monophosphorylated amidinium salts 6 and 10 respectively. The phosphine oxide 10 is stable, while 6 undergoes an elimination of ethyl chloride to the betain 8. Even under more drastic conditions the reaction of 4 or 8 with TEP does not lead to the expected bis(dimethylamino)bisphosphonate 7, but to the monoaminated bisphosphonate 1, involving a reduction step. Similar reduction has been observed under mild conditions in Michaelis-Arbusov reaction of dichloromethylenimonium chloride, yielding the expected trisphosphonate 2 and the bisphosphonate 1 as a by-product.

Notizen: 6-Substituted 2,4-diphenyl-1,3,4-oxadiazin-5-onesBy reaction of dichloro acetylchloride and β-N-phenyl benzhydrazide 6-chloro-1,3,4-oxadiazin-5-one 2 is accessible which reacts with potassium phthalimide and potassium succinimide, respectively, to from 6-phthalimido- and 6-succinimido 2,4-diphenyl-1,3,4-oxidiazinon (3 and 4), respectively. The phthalimido substituent can be substituted by benzylamine or hydrazine.

Notizen: Untersuchungen an Lactamen. II. Synthese neuer β-Lactame

Notizen: Reactions of β-Chlorovinylaldehydes. IV. Syntheses of 2-Formylmethylene-2H-1-benzopyranes and Benzopyrylocyaninedyes from β-Chlorovinylaldehydesα-Alkyl-β-chlorocrotonaldehydes react with salicylaldehyde in methanolic solution of potassium hydroxide forming 2-formyl-methylene-2H-1-benzopyranes 1. The corresponding benzopyryliumsalts 2 which are easily available from 1 and strong acids, exist in the enolic form. They react at room temperature in alcoholic solution with elimination of ethyl formiate, yielding dark blue compounds which were identified as 2,2′-benzopyrylotrimethincyanindyes 3. The structure of 3 has been elucidated by means of 1H-n.m.r.-spectra.

Notizen: Kinetics of Hydrogen-Deuterium-Exchange in the Methin Chain of Simple PolymethinesSimple polymethines are deuterated in the methin chains at positions of high π-electronic density. The rate constants of this reaction were determined by 1H-n.m.r. spectroscopy taking into account hydrolytic side-reactions. The rate constants of the H/D exchange correlate well with the HMO localization energies at the methin atoms concerned.

Notizen: Reaction of Cyclobutendiones. LIII. New Heterocyclic Systems by Reaction of 4-[-(z)-Benzylidenene]-2,3-diphenyl-cyclobut-2-enone with DiazomethaneThe addition of diazomethane to stable 4-alkylidene-cyclobut-2-enones gives at the same time the 1:1 adducts 2, and under elimination of 1 mole nitrogene the 1:2 adducts 3 respectively the 1:3 adducts 4.

Notizen: 1,2,3-Triazabutadienes. VIII. Investigations of the Mechanism of the Sensitized Photoisomerization of 1-Aryl-3-[3-methyl-benzthiazolinyliden-(2)]-triazenes.It is possible to sensitize the photochemical cis-trans-isomerization of triazabutadienes by sensitizers with tripletenergies ranging from 40 to 80 kcal/mol. It was proved by flash photolysis that triazabutadienes quench the triplet states of sensitizers. The dependence of the photostationary state on the triplet energy of the sensitizer as well as the dependence of the quantum yields of the sensitized photoisomerization on the concentration of triazabutadiene were investigated, and the desactivation ratios of the sensitized photoisomerization were determinated. The found correspondence of desactivation ratios of the direct and sensitized photoisomerization make a triplet mechanism in both cases probable.

Notizen: On the Chemistry of Acylthioureas. III. Synthesis of 1,3,5-Thiadiazine-2-thiones by the Reaction of Acylisothiocyanates with AminesIn course of synthesis of benzoyl-thioureas from benzoyl-isothiocyanate and sec. amines some new 6-amino-4-phenyl-1,3,5-thiadiazine-2-thione 5 are prepared and characterized chemically and spectroscopically.

Notizen: Cyanic Acid Esters. 25 The Reaction of Mercapto-N-heterocycles with Aryl CyanatesUnsaturated N-heterocycles containing a cyclic thio urea structure and aryl cyanates (molar ratio 1:2), react to form azolo(1,2-d) (1,2,4)thiadiazoles. This reaction has a wide scope concerning starting materials and gives good yields. Under the same conditions 2-thione-benzthiazolin is transformed to the corresponding disulfide. 4,5-Bis-mercaptomethylene-o-xylene and aryl cyanates give 2,3-dithia-6, 7-dimethyl-tetraline.

Notizen: Potentielle Psychopharmaka. IV. Synthese von Fluorindolen und verwandten Verbindungen

Notizen: Deactivation Behaviour of Arenes and Heteroarenes. XI. The Evidence of Radiationless Deactivating Excimers by Resonance-Energy TransferInvestigations of resonance-energy transfer in the systems of anthracene-/ and akridizinium ion/rhodamine B (BF4) show, that in the case of high concentrations of energy donors the amount of the relative fluorescence quantum yield is greater than one. This result demonstrates the existence of a further energy donor, the excimer. In the case of the N-methyl-acridinium ion/ rhodamine B (BF4)-system this fact cannot be observed, therefore a formation of excimers at high concentrations should be excluded. The existence (anthracene, akridizinium ion) and non-existence (N-methylacridinium ion) of excimers is in agreement with the ability of forming photodimers.

Notizen: Thiophosphorylierung von Alkoholen im Vier-Komponenten-System: Ph3P/CCl4/(C2H5O)2P(S)OH bzw. (C2H5O)2P(S)SH/(C2H5)3NBei der Reaktion in dem Vier-Komponentensystem (Thio- und Dithiophosphorsäure-O, O-diethylester 2 bzw. 6 -Triphenylphosphin-Tetrachlorkohlenstoff-Triethylamin) und Alkoholen entstehen die Thiolester 3/4 bzw. 7/4 als Hauptprodukte. Ein möglicher Mechanismus der nicht eindeutig verlaufenden Thiophosphorylierungsreaktion wird formuliert. Es werden Thiophosphoryloxyphosphonium-Komplexe als Zwischenprodukte, ihr dynamisches Gleichgewicht und der Zerfall postuliert. Analoge Komplexe, die sich in verwandten Reaktionen als Zwischenprodukte bilden, wurden ebenfalls untersucht.

Notizen: Insertion of CS into AminosilanesDithiocarbamats 2, 3 and 4 with Si—S bondings can be prepared by the insertion of CS2 into aminosilanes 1. It is shown that more than one Si—N bond in a molecule are able to react with CS2. The reactivities of the aminosilanes depend on the basicity of nitrogen. The insertion reaction can be observed by 1H n. m. r. spectroscopy.

Notizen: A Comparison between Different Coupling Methods in the Synthesis of the N-terminal Nonapeptide of the Sheep Insulin-A-Chain by Fragment Condensation on a Solid SupportThe N-terminal protected nonapeptide of the sheep insulin-A-chain, benzyloxycarbonyl-glycyl-isoleucyl-valyl-γ-tert.-butyl -glutamyl-glutaminyl-S-benzylcysteinyl-S-benzylcysteinyl- alanyl-glycine-methylester, was prepared by 4 + 2 + 2 + 1 - P fragment condensations on a solid support by means of various coupling methods, and detached from the matrix by transesterification with methanol. The best results of the fragment couplings have been obtained by means of the dicyclohexylcarbodiimide/pentafluorphenol-complexNomenklatur und Abkürzungen nach den Regeln der IUPAC-IUB-Commission on Biochemical Nomenclature, J. Biol. Chem. 241, 2491 (1966) u. 247, 977 (1972); weitere Abkürzungen: HOSu = N-Hydroxysuccinimid, HOBt = N-Hydroxybenzotriazol, HOOBt = 3-Hydroxy-4-oxo-3,4-dihydro-1,2,3-benzotriazin, EEDQ = 1-Ethoxycarbonyl-2-ethoxy-1,2-dihydrochinolin, Woodwards Reagens = 2-Ethyl-7-hydroxy-1,2-benzisoxazolium-tetrafluoroborat, NEPIS = 2-Ethyl-5-phenyl-1,2-oxazolium-3′-sulfonat, DCCI = Dicyclohexylcarbodiimid, PfpOH = Pentafluorphenol, Ph3P = Triphenylphosphin, (PyS)2 = 2,2′-Dipyridyldisulfid, Z = Benzyloxycarbonyl-, Nps = o-Nitrophenylsulfenyl-, Boc = tert.-Butyloxycarbonyl-, Bzl = Benzyl-, -OMe = Methylester, -OBut = tert.-Butylester, THF = Tetrahydrofuran, DMF = Dimethylformamid, Et3N = Triethylamin, NMM = N-Methylmorpholin, TFA = Trifluoressigsäure. and by the oxidation-reduction condensation method wich 2,2′-dipyridyldisulfide and triphenylphosphine. Using dicyclohexylcarbodiimide/hydroxybenzotriazole or EEDQ the optical purity results were insufficient and the yields of the fragment condensations much smaller in comparison with the other mentioned methods.

Notizen: A Method for the Quantitative Control of Solid Phase Reactions in the Peptide SynthesisA quantitative control-method of partial steps of a solid phase peptide synthesis is described, based on a hydrazinolytic cleavage of protected peptides from the solid support. A separation of the peptide hydrazides by gelchromatography on sephadex G 15 in dimethylformamide and a quantitative evaluation of the hydrazide-content in the elution fractions is reported, which permits the control of the Nα-deprotection step in the same way as the evaluation of the coupling yields of the desired sequence. The new method is discussed for the example of two solid phase syntheses of the pentapeptide N-tert.-butyl-oxycarbonyl-L-valyl-S-benzyl-L-cysteinyl-L-alanyl-L- leucyl-O-benzyl-L-tyrosine hydrazide.