Helvetica Chimica Acta

doi: 10.1002/hlca.19740570501pmid: N/A

Keller, Oskar; Rudinger, Josef

doi: 10.1002/hlca.19740570502pmid: 4854571

Starting from a selectively protected derivative of α,α′‐diaminosuberic acid (3) the linear protected peptide 11 has been obtained. Cyclisation to 12 followed by removal of the protecting groups by hydrogenolysis afforded the ‘dicarba’ analogue of oxytocin, 1 c, which showed about 5 IU/μmol of uterotonic activity in vitro.

Chapleo, Christopher B.; Dreiding, André S.

doi: 10.1002/hlca.19740570503pmid: N/A

Homo‐p‐chinon (4 = Bicyclo[4.1.0]hept‐3‐en‐2,5‐dion) wurde hergestellt und auf seine Spektraleigenschaften untersucht. Die UV.‐, IR.‐ und NMR.‐Spektren sind charakteristisch für die darin enthaltene Endion‐und cis‐disubstituierte Cyclopropan‐Substruktur, ohne eine starke Wechselwirkung zwischen den beiden zum Ausdruck zu bringen.

Bieri, Gerhard; Heilbronner, Edgar; Kloster‐Jensen, Else; Schmelzer, Andreas; Wirz, Jakob

doi: 10.1002/hlca.19740570504pmid: N/A

The photoelectron spectra of 1,5‐cyclooctadiyne (2) and of 1,6‐dithiacyclodeca‐3,8‐diyne (3) have been recorded. The first four (2) or six (3) PE. bands have been assigned as follows; in increasing order of ionization potentials: \documentclass{article}\pagestyle{empty}\begin{document}$$ 2:\,2{\rm b}_{{\rm 2g}} (\pi),\,6{\rm b}_{{\rm 1u}} (\pi),\,7{\rm a}_{\rm g} (\pi),\,2{\rm b}_{{\rm 3u}} (\pi) $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ 3:\,14{\rm a}_{\rm g} ({\rm n}),\,9{\rm a}_{\rm u} (\pi),\,13{\rm b}_{\rm u} ({\rm n}),\,12{\rm b}_{\rm u} (\pi),\,8{\rm b}_{\rm g} (\pi),\,13{\rm a}_{\rm g} (\pi) $$\end{document}

Wirz, Jakob

doi: 10.1002/hlca.19740570505pmid: N/A

The photochemical reactivity of the title compound 3 was studied in the context of a novel acid catalysed photocyclisation reaction recently discovered by Barton et al. [1b]. The following results were obtained by flash photolysis methods and steady state irradiations in the presence and absence of quenchers and sensitisers combined with luminescence measurements: The fluorescence of 3 in benzene is very weak and short‐lived (ϕF1 ≤ 10−4, τF1 ≤ 10−9 s) due to efficient intersystem crossing (ϕT = 0.8 ± 0.15). On the other hand, the conjugate acid 4 exhibits an intense green fluorescence (ϕF1 = 0.97 ± 0.1) with a lifetime of (4. ± 1.) · 10−9 s. Acidity constants of 4 in the ground and first excited triplet state were estimated in acetic/trifluoroacetic acid mixtures by comparison with Hammett indicators: pK(S0) = −0.3, pK(T1) = +1.

Renold, Walter; Näf‐Müller, Regula; Keller, Urs; Willhalm, Bruno; Ohloff, Günther

doi: 10.1002/hlca.19740570506pmid: N/A

A total of 68 constitutents, mainly aldehydes, ketones and esters, have been identified for the first time in a black tea aroma concentrate using coupled gas‐chromatography/mass spectrometry.

Näf, Ferdinand; Decorzant, René

doi: 10.1002/hlca.19740570507pmid: N/A

The reaction between (Z)‐1‐alkenyllithium and (E)‐β‐(N, N‐dialkylamino)‐α, β‐alkenals, (E)‐β‐(N, N‐dialkylamino)‐α, β‐alkenones or (E)‐β‐(N, N‐dialkylamino)‐α, β‐alkenoic esters yields mainly (E, Z)‐α, β‐γ, δ‐diunsaturated aldehydes, ketones, or esters and is therefore highly stereospecific.

Näf, Ferdinand; Decorzant, René

doi: 10.1002/hlca.19740570508pmid: N/A

The magnesium 3,3‐dimethylcyclohex‐1‐enolate 1i, formed in the copper catalyzed addition of methylmagnesium iodide to 3‐methylcyclohex‐2‐enone, has been subjected to regiospecific electrophilic reactions such as acylation, alkylation, and aldol condensation in order to find a new access to the damascones, ionones and carotenoids. By way of illustration a new synthesis of γ‐damascone is described.

Hertli, Liselotte; Kaden, Thomas A.

doi: 10.1002/hlca.19740570509pmid: N/A

The formation and dissociation kinetics of the pentaco‐ordinated Cu2+, Ni2+, Co2+ and Zn2+ complexes with 1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane (4‐MeCyclam‐14) was studied by pH‐stat techniques and spectrophotometrically. The rates of the reactions between 4‐MeCyclam‐14 and each of the four metal ions, although slower than normal complexations by a factor of 103−104, closely follow the order Cu2+ > Zn2+ > Co2+ > Ni2+, found for the rate of water exchange. This implies that beside water exchange an other constant factor plays an important role in the rate determing step. The dissociation of the pentaco‐ordinated 4‐MeCyclam‐14 complexes is acid catalyzed. The limiting rate for acid dissociation is not reached even in 2.5M HNO3 in the case of Ni(4‐MeCyclam‐14)2+. From the formation and dissociation rates stability constants have been calculated, which do not show any macrocyclic effect.

Buchs, Armand; Glangetas, Alain; Tronchet, Jean M. J.

doi: 10.1002/hlca.19740570510pmid: N/A

The mass spectra of the O‐isopropylidene derivatives of threo‐ and erythro‐furanose and those of the four C(4) methylated stereoisomers have been studied. Fragmentation modes based upon deuterium labelling, metastable peaks and high‐resolution measurements are proposed. Each stereoisomer can be characterized by its low‐resolution mass spectrum.