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Showing papers in "Helvetica Chimica Acta in 1958"


Journal ArticleDOI
TL;DR: In this article, a simple relation exists between the retention index of a compound on a non-polar stationary phase and its boiling point, which is defined as the ratio of the boiling point of the compound to its retention index.
Abstract: For the characterization of organic substances in gas chromatography a number termed «retention index» is proposed. A simple relation exists between the retention index of a compound on a non-polar stationary phase and its boiling point.

1,916 citations


Journal ArticleDOI
TL;DR: The effects produced in the course of fissure of CBO- and benzyl-groups from peptides containing serine and methionine residues, using HBr and acetic acid, are studied.
Abstract: N-CBO-L-Seryl-L-tyrosyl-L-serine methyl ester and L-methionyl-γ-benzyl-L-glutamate are prepared by different methods. Condensation by the hydrazideazide procedure affords N-CBO-L-seryl-L-tyrosyl-L-seryl-L-methionyl-γ-benzyl-L-glutamate, which is shown to be optically pure by leucine-aminopeptidase digestion. Transformation of the above N-CBO-tripeptide ester to the N-acetyltripeptide ester and condensation by the hydrazide-azide procedure with the above dipeptide gives N-acetyl-L-seryl-L-tyrosyl-L-seryl-L-methionyl-γ-benzyl-L-glutamate. The effects produced in the course of fissure of CBO- and benzyl-groups from peptides containing serine and methionine residues, using HBr and acetic acid, are studied.

181 citations


Journal ArticleDOI
TL;DR: The final octapeptide, L-histidyl- L-phenylalanyl-L-arginyl- l-tryptophanyl-glycyl-ϵ-CBO-L/L-lysyl-l-prolyl-V-valylamide is shown to be optically pure by leucine-aminopeptidase digestion.
Abstract: Trityl-glycyl-ϵ-CBO-L-lysine is condensed with L-prolyl-L-valine methyl ester and, after amidification and splitting of the trityl group, glycyl-ϵ-CBO-L-lysyl-L-prolyl-L-valylamide is obtained This is condensed with ditrityl-L-histidyl-L-phenylalanyl-L-arginyl-L-tryptophane prepared by condensation of ditrityl-L-histidyl-L-phenylalanine with L-arginyl-L-tryptophane methyl ester and saponification Dicyclohexyl-carbodiimide is used as a condensing agent After splitting off the trityl groups, the final octapeptide, L-histidyl-L-phenylalanyl-L-arginyl-L-tryptophanyl-glycyl-ϵ-CBO-L-lysyl-L-prolyl-L-valylamide is shown to be optically pure by leucine-aminopeptidase digestion

114 citations


Journal ArticleDOI
TL;DR: In this paper, the isolation in pure form of the ubiquinone from pig heart is described, and its structure has been established as that of a 2,3-dimethoxy-5-methyl-benzoquinone derivative with a vitamin-K2-like isoprenoid side chain of 50 carbon atoms.
Abstract: The isolation in pure form of the ubiquinone from pig heart is described. From 750 kg raw material 37 g of pure crystalline material could be obtained. Its structure has been established as that of a 2,3-dimethoxy-5-methyl-benzoquinone derivative with a vitamin-K2-like isoprenoid side chain of 50 carbon atoms (I). It is proposed to name this compound ubiquinone(50).

89 citations


Journal ArticleDOI
TL;DR: The structure of vitamin K2, m. p. 54°, was established as 2-methyl-3-all-trans-farnesylgeranylgeranyl-1,4-naphtoquinone by total synthesis and comparison of the synthetic compound with vitamin k2 from putrefied fish meal.
Abstract: The structure of vitamin K2, m. p. 54°, is established as 2-methyl-3-all-trans-farnesylgeranylgeranyl-1,4-naphtoquinone by total synthesis and comparison of the synthetic compound with vitamin K2 from putrefied fish meal. It contains a terpenoid side chain of an odd number of seven isoprene units with 7×5 = 35 C-atoms. In addition, a second vitamin K factor isolated from putrefied fish meal, m. p. 50°, is identified as 2-methyl-3-all-trans farnesylfarnesyl-1,4-naphtoquinone by comparison with a synthetic sample. Moreover eight other compounds of the vitamin K2 series have been synthesized.

83 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that the enrichment in the crystalline phase was detected by a separation parameter which could be calculated from the melting point dlfference of HDO and H/sub 2/O/sup 16/ as well as from the heat of fusion and the absolute fusion temperature.
Abstract: In the stepwise crystallization of water an enrichment of both HDO contained in water and of H/sub 2/O/sup 18/ in the crystalline phase occurs. It was shown that the enrichment in the crystalline phase was detected by a separation parameter which could be calculated from the melting point dlfference of HDO and H/sub 2/O or H/sub 2/O/sup 16/ and H/sub 2/O/sup 18/ as well as from the heat of fusion and the absolute fusion temperature. For the case of deuterium or O/sup 18/ enrichment the separation parameter was experimentally determined. An HDO enrichment of sigma /sub E,W/ w= 1.71 x 10/sup -2/ was obtained in good agreement wtth theoretical values. For the enriehment of H/sub 2/O/sup 18/ a value of sigma /sub E,W/x 10/sup -4/ was obtained. The calculated fusion temperature of H/sub 2/O/sup 18/ was + 0.05 deg . It is possible to multiply the small separation effect observed in the stepwise crystallization of water in a hairpin counter curreat system. For the conditions under which a practical multiplication could be obtained, the magnitude of the diffusion coefficient for D or O/sup 18/ in ice more » is essential. These diffusion coefficients were experimentally determined from -1.5 to -2 deg . They are, within the error limits, identical for D and O/sup 18/ and have the value D =1.0 x 10/sup -10/ cm/ sec. Onthe basis of the measured separation parameter and the diffusion coefficients, the possibility for a multiplication of the isotope separation by a hairpin counter current method was discusssd. (tr-anth) « less

77 citations


Journal ArticleDOI
TL;DR: Farnesiferol A (I) is a mixed ether of umbelliferone with a sesquiterpene moiety of the bicyclofarnesylic type as mentioned in this paper.
Abstract: From the non-volatile, neutral fraction of Asa foedita (Umbelliferae) 3 isomeric compounds C24H30O4, designated farnesiferol A, B, and C, have been isolated. Farnesiferol A (I) is a mixed ether of umbelliferone with a sesquiterpene moiety of the bicyclofarnesylic type. It might arise biogenetically by oxidative cyclisation of the known umbelliprenine (XXXII).

70 citations


Journal ArticleDOI
TL;DR: In this article, a standard method for the determination of apparent dissociation constants of organic acids and bases in the solvent system 80 wt.-% methylcellosolve/20 wt.% water, using samples of 0,1 mg and more, is proposed.
Abstract: A standard method for the determination of apparent dissociation constants of organic acids and bases in the solvent system 80 wt.-% methylcellosolve/20 wt.-% water, using samples of 0,1 mg and more, is proposed.

62 citations


Journal ArticleDOI
TL;DR: In this article, a cyclic process for the fractionation of yttrium earths is described and the existence of a miscibility gap between the salts NH4[R'-EDTA], 8 H2O and NH4 [R″-EDTA]−, 6 H 2O (R′ = elements of the cerium group plus Gd and Tb; R″ = elements Dy to Lu, including Y; EDT.4 = ethylendiamine-tetraacetate) provides an excellent separation.
Abstract: A cyclic process for the fractionation of the yttrium earths is described. The existence of a miscibility gap between the salts NH4[R'-EDTA], 8 H2O and NH4 [R″-EDTA]−, 6 H2O (R′ = elements of the cerium group plus Gd and Tb; R″ = elements Dy to Lu, including Y; EDT.4 = ethylendiamine-tetraacetate) provides an excellent separation. The method is suitable for collecting in a small fraction and with a high yield the traces of the heavy lanthanides present in a mixture containing about 80% (Sin + Gd).

59 citations


Journal ArticleDOI
TL;DR: The reduction of 2-oxo-1,2,3,4,6,7-hexahydro-11bH-benzo[a]quinolizines substituted in 3-position is described in this paper.
Abstract: The reduction of various 2-oxo-1,2,3,4,6,7-hexahydro-11bH-benzo[a]quinolizines substituted in 3-position is described. Depending upon the method of reduction and the experimental conditions applied, either a sterically homogeneous carbinol or a mixture of two epimeric carbinols is obtained. Their stereochemistry is discussed. Various derivatives of these alcohols are described.

58 citations


Journal ArticleDOI
TL;DR: The rotationsdispersionskurve von 1-Keto-steroiden zeigt einen aussergewohnlichen Verlauf.
Abstract: 1 Mit Hilfe von optischen Rotationsdispersionskurven lassen sich bei Cardenolid-Derivaten wie in andern Steroid-Klassen zusatzliche Carbonylfunktionen ohne Schwierigkeiten erfassen. Bei den Bufadienolid-Derivaten ist dies erst moglich, wenn der α-Pyronring in hydrierter Form vorliegt. 2 Die Rotationsdispersionskurve von 1-Keto-steroiden zeigt einen aussergewohnlichen Verlauf. Dies wird durch weitere entsprechende Cardenolid-Derivate sowie durch Modellverbindungen illustriert. 3 Die Abhangigkeit der Rotationsdispersion von Cardenoliden mit einer α-Ketol-Gruppierung in 11,12-Stellung sowohl von der Stereochemie dieser Gruppe selbst als auch von der des Ringgerustes wird unter Heranziehung geeigneter Modelle (Atiansauren, Gallensauren, Sapogenine) untersucht und diskutiert. Zum Vergleich wird die Rotationsdispersion einiger D-Homo-steroide mit einer α-Ketol-Gruppierung in 17α, 17a-Stellung sowie weitere Steroid-Derivate mit einer solchen in 4,5-, 5,6-, 16,17- und 17,20-Stellung bestimmt und diskutiert.

Journal ArticleDOI
TL;DR: Les composes d'addition de l'acetophenone and de la benzophenone avec divers accepteurs electroniques, tels que ZnCl2, FeCl3, BF3 et AlCl3 as mentioned in this paper, ont ete prepares, et leurs spectres infrarouges, etudies a l'etat solide and, pour certains, en solution dans C6H6.
Abstract: Les composes d'addition de l'acetophenone et de la benzophenone avec divers accepteurs electroniques, tels que ZnCl2, FeCl3, BF3 et AlCl3, ont ete prepares, et leurs spectres infrarouges, etudies a l'etat solide et, pour certains, en solution dans C6H6.

Journal ArticleDOI
TL;DR: This paper showed that doubling reaction during cyclization seems to play a greater role in the synthesis of homodetic cyclo-polypeptides than anticipated, especially for peptides containing an odd number of amino acid residues.
Abstract: Attempts to cyclize the p-nitrophenyl esters of the pentapeptides L-valyl-L-(Nδ-tosyl)-ornithyl-L-leucyl-D-phenylalanyl-L-proline and L-valyl-L-(Ne-tosyl)-lysyl-L-leucyl-D-phenylalanyl-L-proline lead to a condensation and cyclization reaction of 2 molecules each of activated esters The cyclic products are identical with those obtained from the corresponding derivatives of the linear decapeptides This kind of doubling reaction during cyclization seems to play a greater role in the synthesis of homodetic cyclo-polypeptides than anticipated The phenomenon might be expected to occur especially well with peptides containing an odd number of amino acid residues

Journal ArticleDOI
TL;DR: In this paper, die gegenseitige Umwandlung von C-Dihydro-toxiferin und Hemi-dihydrin and verwandten Verbindungen dar is discussed.
Abstract: Die vorliegende Arbeit stellt eine Prazisierung und Erweiterung unserer kurzlich veroffentlichten vorlaufigen Mitteilung16) uber die gegenseitige Umwandlung von C-Dihydro-toxiferin und Hemi-dihydro-toxiferin und verwandten Verbindungen dar.

Journal ArticleDOI
TL;DR: In this article, the Konstitution des erstmals im Jahre 1870 isolierten, neuartig gebauten Glucosides Plumierid wurde bestimmt.
Abstract: Die Konstitution des erstmals im Jahre 1870 isolierten, neuartig gebauten Glucosides Plumierid wurde bestimmt. Fur den Naturstoff und seine Abkommlinge wurden wahrscheinliche, absolute Stereoformeln abgeleitet.

Journal ArticleDOI
TL;DR: In this article, the bridgehead-substituted bicyclo-[2, 2,2,2]-octanes Ia, b, c, d and f have been modified and improved.
Abstract: Known procedures for the synthesis of the bridgehead-substituted bicyclo-[2,2,2]-octanes Ia, b, c, d and f have been modified and improved.

Journal ArticleDOI
TL;DR: A new crystalline substance has been isolated from hog adrenals in a yield of about 30 mg per 1000 kg glands and appears to act under certain biological conditions as a sodium excreting factor.
Abstract: A new crystalline substance has been isolated from hog adrenals in a yield of about 30 mg per 1000 kg glands. It appears to act under certain biological conditions as a sodium excreting factor. This compound is shown to be 3β,16α-dihydroxy-allopregnan-20-one; several syntheses of it as well as a number of derivatives are described.

Journal ArticleDOI
TL;DR: In this paper, a new N-Methyl-dihydro-nicotinsaureamid beschrieben, in welchem sehr wahrscheinlich das 1,6-Dietterivat vorliegt; fur das seit langem bekannte N-methyldihd-drug-nikotin-nicaureamids wird daher in ubereinstimmung mit anderen Autoren die 1,4-Dye-struktur fur wah
Abstract: 2,6-Dimethyl-4-phenyl-3,5-dicarbathoxy-dihydro-pyridin (I), die isomeren 1,2,6-Trimethyl-4-phenyl-3,5-dicarbathoxy-dihydro-pyridine (II und X), 2,4,6-Trimethyl-3,5-dicarbathoxy-dihydro-pyridin (V), die isomeren 1,2,4,6-Tetramethyl-3,5-dicarbathoxy-dihydro-pyridine (III und XI), 2,6-Dimethyl-3,5-dicarbathoxy-dihydro-pyridin (VI) sowie die isomeren 1,2,6-Trimethyl-3,5-dicarbathoxy-dihydro-pyridine (IV und XII) wurden hergestellt, genau untersucht und ihre Konstitutionsformeln ermittelt. UV.- und IR.-Spektren dieser Verbindungen werden mitgeteilt. Ausserdem wird ein neues N-Methyl-dihydro-nicotinsaureamid beschrieben, in welchem sehr wahrscheinlich das 1,6-Dihydroderivat vorliegt; fur das seit langem bekannte N-Methyl-dihydro-nicotinsaureamid wird daher in ubereinstimmung mit anderen Autoren die 1,4-Dihydrostruktur fur wahrscheinlich gehalten.

Journal ArticleDOI
TL;DR: In this paper, the treatment of 7-bromo-cholesteryl esters by trialkyl phosphites in boiling xylene gives the corresponding esters of 7dehydro-cholesterol with excellent yield.
Abstract: Treatment of 7-bromo-cholesteryl esters by trialkyl phosphites in boiling xylene gives the corresponding esters of 7-dehydro-cholesterol with excellent yield. Isolation of the latter is most convenient when the benzoate and trimethyl phosphite are used.

Journal ArticleDOI
TL;DR: In this paper, the synthesis of hexabenz-1,12;2,3;4,5;6,7;8,9;10,11-coronene, using two different reaction schemes is described.
Abstract: The synthesis of hexabenz-1,12;2,3;4,5;6,7;8,9;10,11-coronene, using two different reaction schemes is described. The cyclodehydrogenation of hexaphenylbenzene, and the reaction of dibenz-1,9;2,3-anthrone with Zn/ZnCl2 lead to identical products, the chemical and crystallographic properties of which demonstrate the structure of hexabenzcoronene. Furthermore, two other hydrocarbons have been isolated from the reaction of dibenzanthrone with Zn/ZnCl2. The UV. spectrum of the first, and its cyclization to hexabenzcoronene show that it is tetrabenz-4,5;6,7;11,12;13,14-peropyrene. The properties of the second indicate that it is tetrabenz-1,2;3,4,8;9; 10,11-bisanthene.

Journal ArticleDOI
TL;DR: In this paper, the synthesis of octapeptides with the amino acid sequence of Val5-hypertensin I has been repeated several times, yielding the purest intermediates and products.
Abstract: The preliminarily published synthesis(4) of decapeptides with the amino acid sequence of Val5-hypertensin I has been repeated several times. The products showed a high hypertensive activity, comparable with that of the corresponding octapeptides [Val5-hypertensin II and Val5-hypertensin II-Asp-β-amide(12)]. The synthesis yielding the purest intermediates and products is described in this paper. The high chemical purity of the synthetic Val5-hypertensin I and Val5-hypertensin I-Asp-β-amide was ascertained by countercurrent distribution, paper chromatography, elemental analysis, and determination of amino acids after hydrolysis. The free, crystalline peptides H · Val-Tyr · OH (L–L), H · Val-His · OH (L–L), H · Val-Tyr-Val · OH (L3), H · Val-Tyr-Val-His · OH (L4) and H · Pro-Phe · OH (L–L) were prepared from intermediates of the synthesis.

Journal ArticleDOI
U. O. Gloor1, O. Isler1, R. A. Morton1, R. Rüegg1, O. Wiss1 
TL;DR: In this paper, the ubiquinone compound isolated from baker's yeast has been identified as 2,3-dimethoxy-5-methyl-6-all-trans-farnesylfarnesyl-1,4-benzoquinone.
Abstract: An ubiquinone compound isolated from baker's yeast has been identified as 2,3-dimethoxy-5-methyl-6-all-trans-farnesylfarnesyl-1,4-benzoquinone by its total synthesis starting from 2,3-dimethoxy-5-methyl-hydroquinone and all-trans-farnesylnerolidol. The name ubiquinone(30) is proposed for this compound.

Journal ArticleDOI
TL;DR: In this paper, the synthesis of two octapeptides, H · Asp(β-NH2)-Arg-Val-Tyr -Val-His-Pro-Phe · OH and H ·Asp( β-OH)-Arg -Val −Tyr −Val −Pro-ProPhe· OH, is described in detail.
Abstract: The synthesis of two octapeptides, H · Asp(β-NH2)-Arg-Val-Tyr-Val-His-Pro-Phe · OH and H · Asp(β-OH)-Arg-Val-Tyr-Val-His-Pro-Phe · OH, is described in detail (preliminary communications see footnote 3). The products show a very strong hypertensive activity, and may be identical with the hitherto unknown Val5-hypertensin II of ox blood.

Journal ArticleDOI
TL;DR: In this paper, convenient methods to obtain 2-phenyl-3-amino-pyrazole, a compound not reported in the literature, are described, which is the aminocomponent of a sulfonamide with an outstanding chemotherapeutic effect.
Abstract: Convenient methods to obtain 2-phenyl-3-amino-pyrazole, a compound not reported in the literature, are described. The substance is the aminocomponent of a sulfonamide with an outstanding chemotherapeutic effect.

Journal ArticleDOI
TL;DR: In this article, the authors discuss the kurzer Einwirkung von Bromsuccinimid auf β-Carotin in Gegenwart von Alkohol (C2H5OH, CH3OH) and nachfolgender Behandlung des Reaktions-produktes with starken Bason (N-Athylmorpholin, N-ATHylpiperidin usw.) bilden sich 4,Athoxy- und 4,4′-Diathoxy-β
Abstract: Bei kurzer Einwirkung von Bromsuccinimid auf β-Carotin in Gegenwart von Alkohol (C2H5OH, CH3OH) und nachfolgender Behandlung des Reaktions-produktes mit starken Bason (N-Athylmorpholin, N-Athylpiperidin usw.) bilden sich 4-Athoxy- und 4,4′-Diathoxy-β-carotin bzw. 4-Methoxy- und 4,4′-Dimethoxy-β-carotin; ferner 4-Keto-4′-methoxy-β-carotin bzw. 4-Keto-4′-athoxy-β-carotin, sowie 4,4′-Diketo-β-carotin und Retro-dehydro-carotin.

Journal ArticleDOI
TL;DR: In this article, eine ergiebige Uberfuhrung des (−)-Sclareols in (+)-Manool beschrieben, die auf der selektiven Esterpyrolyse des Di-O-acetyl-(−)-sclareols beruht.
Abstract: Es wird eine ergiebige Uberfuhrung des (−)-Sclareols in (+)-Manool beschrieben, die auf der selektiven Esterpyrolyse des Di-O-acetyl-(−)-sclareols beruht.

Journal ArticleDOI
TL;DR: Phenylazo-benzyloxy-carbonylchlorid (PZ-Chlorid) and p-(p′-Methoxyphenylazoenylazo)-benzinoxy-carbonyl chlorid (MZ-CCLid) sind ausgezeichnet kristallisierte, stabile Verbindungen, welche sich mit Aminogruppen von Aminosauren and Peptiden zu organgelben Derivaten umsetzen lassen.
Abstract: p-Phenylazo-benzyloxy-carbonylchlorid (PZ-Chlorid) und p-(p′-Methoxyphenylazo)-benzyloxy-carbonylchlorid (MZ-Chlorid) sind ausgezeichnet kristallisierte, stabile Verbindungen, welche sich mit Aminogruppen von Aminosauren und Peptiden zu organgelben Derivaten umsetzen lassen. Wie die klassische Carbobenzoxygruppe (Z-) lassen sich die PZ- und MZ-Gruppen durch Hydrierung oder mit HBr in Eisessig leicht wieder spalten. Deshalb und weil Chromatogramme und multiplikative Verteilungen leicht kolorimetrisch ausgewertet werden konnen, durften diese neuen Schutzgruppen fur die Synthese und Isolierung von Polypeptiden grosse Vorteile bieten.

Journal ArticleDOI
TL;DR: An oxidation-reduction function during the early phases of growth is suggested for the system: γ -glutamyl-S-methylcysteine/ γ-glut amyl- S-methyl Cysteine sulfoxide.
Abstract: γ -Glutamyl-S-methylcysteine has been isolated from extracts of lima beans (Phaseolus lunatus L.). Two further peptides, γ -glutamyl-S-methylcysteine sulfoxide and γ -glutamyl-leucine have been tentatively identified. In addition, free S-methylcysteine was found in such extracts. The presence of these constituents in varying amounts was observed in all of 6 other varieties of beans that were investigated. During germination S-methylcysteine and all peptides occurring in lima beans are metabolized to unknown products. An oxidation-reduction function during the early phases of growth is suggested for the system: γ -glutamyl-S-methylcysteine/ γ -glutamyl-S-methylcysteine sulfoxide.

Journal ArticleDOI
TL;DR: Jamaicin aus Piscidia erythrina L. wird als Isoflavon erkannt und in seiner Struktur aufgeklart as mentioned in this paper.
Abstract: Jamaicin aus Piscidia erythrina L. wird als Isoflavon erkannt und in seiner Struktur aufgeklart. Fur den oxydativen Abbau der Isoflavone wird eine modifizierte Ausfuhrung der alkalischen Wasserstoffperoxyd-Oxydation angegeben.

Journal ArticleDOI
TL;DR: In this paper, the spectre d'absorption infrarouge des composes d'addition acetone-BF3 and di-npropyl-cetone -BF3 en dispersion dans le nujol et en solution benzenique.
Abstract: Les auteurs ont etudie le spectre d'absorption infrarouge des composes d'addition acetone-BF3 et di-n-propyl-cetone-BF3 (compose nouveau) en dispersion dans le nujol et en solution benzenique. La bande d'absorption caracteristique des cetones vers 1710 cm−1 est remplacee par une nouvelle frequence d'absorption, d'intensite comparable, situee environ 70 cm−1 plus bas. L'interpretation donnee est la formation d'une liaison de coordination entre les atomes de bore et d'oxygene, modifiant la repartition electronique au voisinage de ce dernier atome.