15N-NMR spectroscopy. III. Neighboring residue effects in sequence polymers containing glycylglycine units

The tripeptides Phe-Gly-Gly, β-Ala-Gly-Gly, and ?-Aca-Gly-Gly as well as the peptide derivatives δ-isothiocyanatovaleroyl-Gly-Gly and ?-isothiocyanatocaproyl-Gly-Gly were synthesized by using known methods so that the peptide nitrogen between the two glycyl residues was isotopically enriched in ¹⁵N to a level of 0.8–0.9%. These monomer units were then used to produce the sequence polymers (Phe-Gly-Gly)_n, (β-Ala-Gly-Gly)_n, (δ-Ava-Gly-Gly)_n, and (?-Aca-Gly-Gly)_n. The 18.24 MHz ¹⁵N-NMR spectra of the oligo- and polypeptides were obtained by using trifluoroacetic acid as solvent, since the solutions have relatively low viscosity and exhibit a strong negative nuclear Overhauser enhancement of the ¹⁵N signals. For comparison, ¹⁵N-NMR spectra of the homopolymers (Gly)_n, (β-Ala)_n, (γ-Abu)_n, (δ-Ava)_n, and (?-Aca)_n were also recorded. The ¹⁵N signals from the ω-aminoacyl residues in the sequence polymers appear up to 11 ppm upfield of the signals observed for the homopolyamides. The ¹⁵N signals from the two glycyl residues are separated by 3–7 ppm. Comparison with the ¹³C-NMR spectra of the same polymers indicates that ¹⁵N-NMR is better suited for the characterization and sequence analysis of these types of polymers.     

L'acide hydroxylamine-O-sulfonique,réactif de choix pour la conversion d'aldéhydes en nitriles

Hydroxylamine-O-sulfonic acid: a convenient reagent for the conversion of aldehydes into nitriles . Hydroxylamine-O-sulfonic acid (HAS) proved to be an excellent reagent for the conversion of aliphatic, aromatic and heteroatomic aldehydes into nitriles. There, aldehydes in the form of suspension in HAS water solution, react rapidely to give the corresponding nitriles in high yield. Only with formylpyridines could the intermediate oxime-O-sulfonic acids be isolated.     

Fluorescence from the second excited singlet state of [18] annulenes

The emission spectra of the second excited singlet state of [18] annulene and of monofluoro [18] annulene (in a 3-methylpentane glass at 4 K) are reported. The large energy gap between the first and second excited singlet states inhibits fast internal conversion and favours the appearance of S₂ → S₀ emission. In addition, fluorescence from the S₁ state can be observed in monofluoro [13] annulene by exciting into the S₂ or directly into the S₁ absorption.     

Substituted γ-lactones: On the structural elucidation of the reaction products from 4-aroyl-3-hydroxy-2(5H)-furanones and 1,2-diamines

The reaction pathway of 4-aroyl-3-hydroxy-2(5H)-furanones 1 with diamines depends on the nature of the amine as well as on the applied reaction conditions. Thus, the reaction of 1a-d with 5,6-diamino-1,3-dimethyluracil 5 led to the formation of two isomeric Schiff bases 7a-d and 8a-d . Conversely type 1 compounds reacted with 4,5-diaminopyrimidine 9 or 2,3-diaminopyridine 10 to form the mono acid-base adducts 11a and 11b respectively. When type 1 compounds were reacted with aliphatic diamines 13a-d or p-phenylenediamine and p-xylenediamine, respectively also an immediate formation of acid-base adducts 15a-f was observed. The reaction of a number of O-methylated type 1 compounds with 1,2-ethylenediamine afforded the novel seven-membered ring compounds 18a-d in good yields. The analogous reaction of O-alkylated 1a with o-phenylenediamine 2 or 2,3-diaminonaphthalene gave the expected tricyclic ring systems 19 or 20 .     

Chemische Konstitution und Zellstreckungswirkung verschiedener Stoffe

Zusammenfassung Die Pastenmethode gestattet als einziger Zellstreckungstest fördernde und hemmende Wirkungen von außen zugeführter Stoffe am normal gesteuerten pflanzlichen Streckungswachstum gleichzeitig und gleichwertig festzustellen und zu messen. Ihre Beziehung zu anderen Testmethoden wird diskutiert.Auf Grund einer einfachen Überlegung über die allgemeinen Wirkungsmöglichkeiten von Wirkstoffen innerhalb der von ihnen beeinflußten Systeme wird eine allemeine Wirkstoffhypothese entwickelt, welche annimmt, daß ein Wirkstoff entweder eine Wirkgruppe und eine Affinität zu einer Wirklücke oder eine Hemmgruppe und eine Affinität zu einer Hemmlücke oder aber beides haben muß, wenn er Wirkstoffeigenschaften besitzen soll. Die im speziellen Fall als Gruppen oder Affinitäten bezeichneten Strukturbereiche können sich auch überschneiden oder untereinander identisch sein, doch ist ihre anfänglich getrennte Betrachtung aus heuristischen Grüden in jedem Falle zweckmäßig. Beliebige Stoffe können jeweils eine oder mehrere der genannten Gruppen oder Affinitäten in verschiedenen Stärken aufweisen und sich im Wirkstoffsystem dementsprechend verhalten. Es wird eine Deutung verschiedener Konzentrations-Wirkungskurven auf Grund dieser Hypothese gegeben.Die Kennzahlen der Konzentrations-Wirkungskurven von über 50 verschiedenen Stoffen im Pastentest werden mitgeteilt und vergleichend diskutiert.Mit 5 Abbildungen.Die hier veröffentlichte Wirkstoffhypothese wurde zusammen mit einem Teil des Materials dieser Mitteilung am 13. 8. 1953 beim Wuchsstoff-symposium der Universität Lund/Schweden erstmals vorgetragen.     

Biradicals/zwitterions from thermolysis of enyne-isocyanates. Application to the synthesis of 2(1H)-pyridones, benzofuro[3,2-c]pyridin-1(2H)-ones, 2,5-dihydro-1H-pyrido[4,3-b]indol-1-ones, and related compounds

Thermolysis of benzannulated enyne-isocyanates 13 and enyne-isocyanates 36 and 37 promoted the cycloaromatization reactions to generate in situ O,4-didehydro-2-hydroxyquinolines and O,4-didehydro-2-hydroxypyridines, respectively, as reactive intermediates. These cycloaromatized intermediates could be captured either as biradicals and/or as zwitterions depending on the nature of the substituent at the alkynyl terminus. The intermediate derived from cycloaromatization of 13a bearing a phenyl substituent could be regarded as biradical 14, which then abstracts hydrogen atoms from gamma-terpinene leading to 2(1H)-quinolinone 15. Alternatively, the same intermediate could also be regarded as zwitterion 14', which then undergoes an initial hydride abstraction from gamma-terpinene followed by protonation to produce 15. The presence of a 2-phenylethyl substituent in 13b and 37a or a 2-methylphenyl substituent in 37b also allowed the resulting intermediates to be captured intramolecularly either as biradicals or as zwitterions, producing 2(1H)-quinolinone 19, 2(1H)-pyridone 39, and benzopyranopyridine 43, respectively. On the other hand, with a 2-methoxyphenyl, a 2-(dimethylamino)phenyl, or a 3-methoxypropyl substituent, the chemical behavior of the cycloaromatized adduct could be best accounted for in terms of a zwitterionic intermediate leading to benzofuro[3,2-c]quinolin-6(5H)-one (20), 5,11-dihydro-11-methyl-6H-indolo[3,2-c]quinolin-6-one (25), benzofuro[3,2-c]pyridin-1(2H)-one 44, 2,5-dihydro-2,5-dimethyl-1H-pyrido[4,3-b]indol-1-one 46, and related compounds. Interestingly, thermolysis of 37f bearing a 2-(methoxymethyl)phenyl substituent at the alkynyl terminus produced the unexpected benzopyranopyridine 56 as the major product in a process involving the cleavage of the bond between the methoxyl oxygen and the adjacent methylene carbon. The efficiency and selectivity of the cycloaromatization reaction could also be enhanced by the introduction of 1.1 to 10 equiv of dimethylphenylsilyl chloride to the reaction mixture to capture the resulting zwitterion.     

Relaxation processes in room temperature ionic liquids: the case of 1-butyl-3-methyl imidazolium hexafluorophosphate

A detailed investigation on the nature of the relaxation processes occurring in a typical room temperature ionic liquid (RTIL), namely, 1-butyl-3-methyl imidazolium hexafluorophosphate ([bmim][PF(6)]), is reported. The study was conducted using both elastic and inelastic neutron scattering over a wide temperature range from 10 to 400 K, accessing the dynamic features of both the liquid and glassy amorphous states. In this study, the inelastic fixed energy scan technique has been applied for the first time to this class of materials. Using this technique, the existence of two relaxation processes below the glass transition and a further diffusive process occurring above the glass-liquid transition are observed. The low temperature processes are associated with methyl group rotation and butyl chain relaxation in the glassy state and have been modeled in terms of two Debye-like, Arrhenius activated processes. The high temperature process has been modeled in terms of a Kohlraush-Williams-Watts relaxation, with a distinct Vogel-Fulcher-Tamman temperature dependence. These results provide novel information that will be useful in rationalizing the observed structural and dynamical behavior of RTILs in the amorphous state.     

Investigation on anodized aluminium

Results of examinations with TEM, SEM, EDX, ISS, SIMS and AES on sulphuric acid anodized films on aluminium are reported. Important technical information about the 20-μm thick coatings were obtained by monolayer and depth analysis. The fine structure of the oxide film and its modifications during a sealing process are discussed. Possibilities to prevent sealing smut on the surface are shown. The metal distribution inside the films which are coloured electrolytically with metal salts, is investigated.