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  • 1985-1989
  • 1980-1984  (739)
  • 1965-1969  (561)
  • 1890-1899
  • 1981  (739)
  • 1968  (561)
  • Organic Chemistry  (1,261)
  • Insulin
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Years
  • 1985-1989
  • 1980-1984  (739)
  • 1965-1969  (561)
  • 1890-1899
Year
  • 1
    ISSN: 1432-1440
    Keywords: Glucose tolerance ; Insulin ; Diabetogenic hormones ; Caerulein ; Man ; Glukosetoleranz ; Insulin ; Diabetogene Hormone ; Caerulein ; Mensch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Untersucht wurden 11 gesunde Personen, fünf Typ I und ein Typ II Diabetiker. Nach einer 12stündigen Fastendauer wurde Caerulein (20 ng/kg) i.v. injiziert und 60 Minuten später eine orale Glukosebelastung mit 100 g bei den Gesunden und 25 g Glukose bei den Diabetikern durchgeführt. Blutdruck, Puls, Blutglukose, Serum-Insulin, Glucagon, Prolaktin und Wachstumshormon wurden während der gesamten Testdauer von 240 min in regelmäßigen Abständen gemessen und mit den Werten einer Kontrolluntersuchung bei den gleichen Personen ohne Caerulein verglichen. Caerulein führte zu keiner signifikanten Änderung einer der gemessenen Parameter. — Während Caerulein die exokrine Pankreasfunktion stark stimuliert, hat dieses Decapeptid keinen Einfluß auf Glukosetoleranz und Funktionen des endokrinen Pankreas und der Hypophyse.
    Notes: Summary Eleven healthy volunteers, five type I diabetics, and one type II diabetic man were examined. After an overnight fast caerulein (20 ng/kg) was injected intravenously and 60 min later an oral glucose tolerance test was performed with 100 g glucose in the normals and 25 g glucose in the diabetics. Blood pressure, pulse rate, blood glucose, serum insulin, glucagon, prolactin and growth hormone values were measured during the whole period of 240 min and compared with the same parameters in control tests in the same persons without caerulein application. None of the measured parameters were significantly influenced by caerulein. It is therefore concluded that in contrast to the stimulation of the exocrine pancreas functions of the endocrine pancreas, the pituitary gland and glucose tolerance are unchanged after caerulein.
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  • 2
    ISSN: 1432-1440
    Keywords: Alanine ; Postoperative metabolism ; Gluconeogenesis ; Protein-catabolism ; Insulin ; Glucagon ; Alanin ; Postoperativer Metabolismus ; Glukoneogenese ; Eiweißkatabolismus ; Insulin ; Glukagon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei sieben Patienten wurde am 1. postoperativen Tag nach Cholecystektomie eine achtstündige Alanininfusion (90 mg/kg/h) durchgeführt und der Einfluß des erhöhten Plasmaalaninspiegels auf die postoperative Stoffwechselsituation untersucht. Folgende Metaboliten und Hormone wurden im Plasma bestimmt: Glukose, Harnstoff, freie Fettsäuren, Ketonkörper, Aminosäuren, Insulin und Glukagon. Gegenüber den Basalwerten (1. postoperativer Tag, nach einer 14stündigen Fastenperiode in der Nacht), vor Beginn der Alanininfusion, wurden folgende Veränderungen festgestellt: Die Plasmaglukosekonzentrationen stiegen bis zur 4. Infusionsstunde an und erreichten hier ein Maximum (p〈0.05). Von den Plasmaaminosäuren erhöhten sich die Konzentrationen von Alanin (um 300%,p〈0.001), Glutamin (36%,p〈0.05) und von α-Aminobutyrat (um 61%,p〈0.01). Die freien Fettsäuren und die Ketonkörper sanken unmittelbar nach Beginn der Alanininfusion ab (p〈0.05) und stiegen ab der fünften Infusionsstunde wieder an. Sowohl die Sekretion von Insulin, als auch die von Glukagon wurde durch die Alaninzufuhr stimuliert. Die Insulinstimulation erreichte bereits nach 5 min ihren maximalen Wert, während die Plasmaglukagonkonzentrationen bis zum Infusionsende anstiegen. Eine Berechnung der Stickstoffbilanz ergab nach der Korrektur mit den angestiegenen Plasmaharnstoffwerten eine ausgeglichene Proteinhomöostase unter der Alaninzufuhr. Die Stickstoffbilanz war, verglichen mit Kochsalzinfusionsperioden vor und nach der Alanininfusion, signifikant verbessert (p〈0.001). Aus den Ergebnissen wird geschlossen, (1) daß postoperativ erhöhte Plasmaalaninspiegel zu einer Stimulierung der Glukoneogenese und einem Konzentrationsabfall der lipolytischen Metaboliten im Plasma führen. Die dabei beobachtete Insulin- und Glukagonstimulation ist je nach der Dauer der Alanininfusion unterschiedlich, da nach einer längeren Alaninzufuhr die Insulinstimulation abnimmt, während die Glukagonstimulation andauert, und (2) daß Alanin in der unmittelbaren postoperativen Phase eine eiweißanabole Wirkung hat.
    Notes: Summary An alanine infusion (90 mg/kg/h) for eight hours was administered to seven patients after cholecystectomy in order to investigate the influence of elevated plasma alanine levels on the postoperative metabolism. The following metabolits and hormone concentrations were analysed in plasma: glucose, urea, free fatty acids, ketone bodies, amino acids, insulin and glucagon. Compared to the pre-infusion values on the 1. postoperative day after an overnight fasting, the following changes were monitored. The plasma glucose concentrations reached a maximum after four hours of infusion (p〈0.05). Of the amino acids, significant elevated levels were found for alanine (300%,p〈0.001), glutamine (36%,p〈0.05), and α-aminobutyrate (61%,p〈0.01). The free fatty acids and ketone bodies concentrations decreased immediately after the onset of the infusion of alanine (p〈0.05), and increased again during the last four hours of infusion. The secretion of insulin and also the secretion of glucagon were stimulated by the increased alanine levels. The stimulation of insulin reached a maximum after only five minutes, but the glucagon levels increased continously until the end of the infusion. During the administration of alanine a nitrogen homeostase was achieved, which was a significant improvement (p〈0.001) when compared to saline infusions before and after the alanine infusion. Conclusions: (1) Postoperative increased plasma levels of alanine stimulate gluconeognesis and reduce the plasma levels of lipolytic metabolites. The induced stimulation of insulin and glucagon is dependent on the duration of the alanine infusion for during extended infusion of alanine the insulin stimulation diminishes while the glucagon secretion continously increases. (2) Alanine is a potent anabolic substrate in the immediate postoperative situation.
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  • 3
    ISSN: 1432-1440
    Keywords: Uremia ; Oral glucose tolerance test ; α-Keto acids ; Insulin ; C-Peptide ; Urämie ; oraler Glukosetoleranztest ; α-Ketosäuren ; Insulin ; C-Peptid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Der Einfluß eines oralen Glukosetoleranztests (oGTT) auf die Serumkonzentrationen verzweigtkettiger Ketosäuren (BCKA), d.h. α-Ketoisocapronsäure (KICA), α-Keto-isovaleriansäure (KIVA) und α-Keto-β-methyl-n-valeriansäure (KMVA) sowie auf die Konzentrationen von Seruminsulin, C-Peptid und Blutglukose wurde bei Urämikern mit kompensierter chronischer Niereninsuffizienz und bei gesunden Kontrollen untersucht. Bei den Kontrollen fielen nach oraler Gabe von 100 g Glukose die Blutkonzentrationen von KICA, KMVA und KIVA signifikant ab. Bei Urämikern ließ sich kein Abfall von KICA nachweisen, während der Abfall von KMVA deutlich vermindert war. Nur die Blutkonzentrationen von KIVA wurden im Verlaufe des oGTT im gleichen Ausmaß gesenkt wie bei den Kontrollen. Sechs von acht Urämikern zeigten eine gestörte Glukosetoleranz, obwohl sich bei ihnen die Konzentrationen von Seruminsulin und C-Peptid vor und während des oGTT nicht signifikant von denen der Kontrollen unterschieden. Die Untersuchungen zeigen, daß der bei Gesunden zu beobachtende Abfall der BCKA-Blutspiegel nach oraler Glukosebelastung bei Urämikern gestört ist. Diese Störung betrifft vorwiegend KICA und ist wahrscheinlich durch Insulinresistenz und/oder durch ungenügende Insulinsekretion bedingt.
    Notes: Summary The effect of an oral glucose tolerance test (oGTT) on serum levels of branched-chain keto acids (BCKA), i.e. α-keto-isocaproic acid (KICA), α-ketoisovaleric acid (KIVA) and α-keto-β-methyl-n-valeric acid (KMVA) as well as on serum insulin, C-peptide and blood glucose levels was determined in uremic patients and in healthy control subjects. In controls, blood levels of KICA, KMVA and KIVA declined significantly following oral administration of 100 g glucose. In uremic patients no declinc of KICA was observed. The fall of KMVA was diminished, while suppression of KIVA blood levels in response to the oGTT remained unimpaired. Although serum insulin and C-peptide levels in uremic patients were not significantly different from the controls before and throughout the oGTT, six out of eight displayed abnormal glucose tolerance. It is suggested that the response of blood BCKA levels to an oGTT is altered in uremia, an abnormality restricted primarily to KICA and possibly explained by insulin antagonism and/or by insufficient insulin secretion.
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  • 4
    ISSN: 1432-0428
    Keywords: Insulin ; obesity ; blood glucose ; plasma non-esterified fatty acids ; low-dose insulin infusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary After an overnight fast, the effects of a 30-min low-dose intravenous insulin infusion (2.6 units/h) upon plasma glucose and non-esterified fatty acids were compared in 29 very obese patients and 17 nonobese controls. The dose of insulin was chosen so as to have its sole or predominant hypoglycaemic effect upon hepatic glucose release. The proportional fall from basal values at 30 min of both plasma glucose and non-esterified fatty acids was significantly greater in the controls and there was no difference between males and females. In the controls the fall in plasma glucose and non-esterified fatty acids was significantly and inversely correlated with the basal plasma insulin level. Neither index of insulin sensitivity was significantly related with the basal plasma insulin in the obese subjects. Weight loss in the obese subjects led to increased insulin sensitivity; in particular, the degree of change in insulin-induced nonesterified fatty acids was significantly related to the percentage change in weight. Despite their extreme degree of obesity, the distributions of basal plasma insulin levels and the indices of insulin sensitivity in the obese subjects overlapped with those of the nonobese controls.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 20 (1981), S. 625-629 
    ISSN: 1432-0428
    Keywords: Insulin ; diabetes ; lysosomal enzymes ; mononuclear cells ; acid cholesterol ester hydrolase ; N-acetyl-β-glucosaminidase ; low density lipoprotein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Methods for the measurement of the lysosomal enzymes acid cholesterol-ester hydrolase and N-acetyl-β-glucosaminidase were adapted for use with freshly isolated circulating mononuclear cells. Activities of both these enzymes increased (to 259 and 147% of control values respectively) after 7 days of insulin therapy in diabetic subjects. Low density lipoprotein degradation by freshly isolated mononuclear cells increased simultaneously by 67% (p〈 0.05). The findings in this pilot study suggest [1] that circulating mononuclear cells can be used to evaluate the effect of metabolic changes in vivo on lysosomal enzymes and low density lipoprotein metabolism, and [2] that insulin can stimulate cellular lysosomal enzyme activity.
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  • 6
    ISSN: 1432-0428
    Keywords: Insulin ; adipocytes ; prednisolone ; dexamethasone ; insulin binding ; deoxyglucose transport ; glucose oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have studied the effects of dexamethasone and prednisolone in vitro and in vivo on insulin binding, deoxyglucose uptake and glucose oxidation in rat adipocytes. In the studies in vivo, rats were treated for 22 h with dexamethasone (30 μg/kg) or prednisolone (200 μg/kg). Following sacrifice, adipocytes were prepared and the results demonstrated that cells from prednisolone treated rats showed a 17% increase in insulin binding and increased rates of basal and insulin stimulated deoxyglucose uptake and glucose oxidation. Conversely, dexamethasone administration resulted in a 22% decrease in insulin binding, and decreased rates of deoxyglucose uptake and glucose oxidation by the cells. Thus, prednisolone and dexamethasone had opposite effects in vivo. In contrast to the opposite effects of the two glucocorticoids in vivo, dexamethasone and prednisolone (each at a concentration of 1 μmol/l) had similar effects on adipocytes in vitro. Incubation of adipocytes with the steroids did not alter insulin binding, while both agents led to a comparable decrease in the rates of basal and insulin stimulated deoxyglucose uptake and glucose oxidation. Thus, dexamethasone and prednisolone have opposite effects on adipocyte glucose metabolism in vivo but have similar effects in vitro.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 21 (1981), S. 165-171 
    ISSN: 1432-0428
    Keywords: Insulin ; sodium ; kidney ; diabetes ; obesity ; hypertension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Data are discussed which demonstrate that insulin plays an important role in sodium metabolism. The primary action of insulin on sodium balance is exerted on the kidney. Increases in plasma insulin concentration within the physiological range stimulate sodium reabsorption by the distal nephron segments and this effect is independent of changes in circulating metabolites or other hormones. Several clinical situations are reviewed: sodium wasting in poorly controlled diabetics, natriuresis of starvation, anti-natriuresis of refeeding and hypertension of obesity, in which insulin-mediated changes in sodium balance have been shown to play an important pathophysiological role.
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  • 8
    ISSN: 1432-0428
    Keywords: Insulin ; insulin receptors ; insulin degradation ; human adipocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 125I-insulin binding and receptor-mediated insulin degradation were studied in isolated human fat cells from subcutaneous tissue. A high albumin concentration during cell isolation and incubation protected the fragile human adipocyte from lysis. Binding of tracer was pH dependent with an optimum between 7.4 and 7.6. At 37 °C steady state was reached by 45 min and maintained for at least 2 h. The binding of labelled insulin in the presence of 10 μmol/l unlabelled insulin was only 1–4% of the total insulin binding. The half-maximal displacement of tracer iodoinsulin (10 pmol/l) by unlabelled insulin occurred at 0.25 nmol/l. Kinetic studies of the dissociation of labelled iodoinsulin from fat cells showed a slight acceleration in the presence of a high concentration of unlabelled insulin in the washout buffer as compared to a buffer containing no insulin. At steady state binding about 95% of the cell-associated radioactivity was extracted as iodoinsulin as judged by gel filtration. The remaining 5% co-eluted with iodotyrosine. During 60 min about 90% of the cell-associated radioactivity dissociated as iodoinsulin and the rest as iodotyrosine. Conclusions: 1) A high albumin content of buffers prevents traumatization of the human adipocyte; 2) under these conditions steady state binding of insulin is readily measured at 37 °C; 3) the use of a washing procedure makes the non-specific binding negligible; 4) the human adipocyte insulin receptor has a very high affinity; 5) receptor-mediated insulin degradation is minimal.
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  • 9
    ISSN: 1432-0428
    Keywords: Insulin ; glucagon ; secretin ; vaso-active intestinal polypeptide ; glucose ; glycerol and 3-hydroxy-butyrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A comparison of the metabolic and gastroentero-pancreatic hormonal responses of ten obese and eight lean subjects to 12 h and 36 h fasts has been made. Each subject was given a 50 g oral glucose tolerance test at the end of both 12 h and 36 h starvation. After the 12 h fast blood glucose and 3-hydroxybutyrate were similar in each group but blood glycerol was 30% higher in the obese subjects. Plasma insulin and vaso-active intestinal polypeptide were also higher in the obese subjects after 12 h starvation. After 36 h starvation in the lean subjects blood glucose was unchanged but on refeeding with 50 g oral glucose, glucose tolerance was impaired. In the same group blood glycerol and 3-hydroxybutyrate rose after 36 h starvation. Plasma glucagon, secretin and vaso-active intestinal polypeptide rose after 36 h starvation in the lean subjects but plasma insulin was unchanged. Refeeding with oral glucose suppressed the increased plasma glucagon, secretin and vaso-active intestinal polypeptide. After the 36 h fast in the obese subjects, blood glucose was unchanged, blood glycerol fell, but blood 3-hydroxybutyrate rose although to a reduced level in comparison with the lean subjects. In the obese group there was no change in plasma glucagon, secretin or vaso-active intestinal polypeptide after 36 h starvation, although plasma insulin fell. The results show different metabolic and gastro-entero-pancreatic hormonal responses to fasting in lean and obese human subjects and suggest an important metabolic role of glucagon, secretin and vaso-active intestinal polypeptide during starvation.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 20 (1981), S. 51-53 
    ISSN: 1432-0428
    Keywords: Insulin ; crystal ; dissolution ; bicarbonate ; pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Insulin is insoluble in water at physiological pH, but dissolves relatively rapidly in plasma. To quantify the ability of various solutions to dissolve crystalline insulin, a simple assay measuring dissolution time was developed. At pH 7.5 and room temperature, distilled water, 0.154 mol/1 NaCl, Ringer's lactate solution, and 5% albumin in 0.154 mol/1 NaCl did not dissolve insulin crystals within 30 min. Normal postprandial human plasma and a proteinfree cell culture medium dissolved insulin crystals within 3 to 8 min. This ability was inhibited by acid titration of the fluids to a stable pH of 6.30, at which point bicarbonate depletion could be implied. Repletion of bicarbonate did restore the ability of these solutions to dissolve insulin crystals, but back-titration to the initial pH with NaOH did not. The effect of sodium bicarbonate alone was strongly concentration dependent above 23 mmol/1. We suggest that the ability of physiological fluids to dissolve insulin crystals at normal pH depends on their bicarbonate content. The ability to dissolve insulin with a physiological solvent which prevents its reaggregation promises to facilitate its use in portable pumping systems.
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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 20 (1981), S. 255-267 
    ISSN: 1432-0428
    Keywords: Insulin ; insulin receptors ; circumventricular organs ; hormone feedback
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The in vivo radioautographic method has been applied to elucidate the mechanism of direct peptide hormone “feedback” action in the CNS. Using this method we have identified the circumventricular organs of the brain as general endocrine target tissues for a variety of blood-borne polypeptide hormones, including insulin. In the arcuatemedian eminence region of the hypothalamus blood-borne insulin directly interacts with receptive nerve terminals, suggesting that insulin acts to influence the electrical activity of select hypothalamic nerve circuits at the level of synaptic transmission. Recent results obtained from preliminary surgical and chemical lesion studies of brain indicate that insulin-receptive nerve terminals in the arcuate-median eminence region arise from neurons intrinsic to the medial basal hypothalamus. This has lead us to propose the concept of the hypothalamic tuberoinfundibular insulin-receptive neuron and its axon collaterals as a pathway for the centripetal flow of insulin “signals” in the form of electrical impulses. We envisige that the neuroanatomic pathway, provided by the hypothalamic tuberoinfundibular neuron, functions to link changes in body metabolic activity, as reflected in changing levels of circulating insulin, to the neuronal process of elaborating specific central metabolic-regulatory programs. This pathway could be of key importance in understanding and combating metabolic disease.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 20 (1981), S. 274-280 
    ISSN: 1432-0428
    Keywords: Insulin ; food intake ; feeding ; CNS ; body weight ; adiposity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A feedback system for the regulation of food intake and body weight, consisting of two elements is proposed. One is related to the quantitiy and quality of the food ingested. It consists of neural afferents, psychosocial conditioning factors, and peptide signals from the gastrointestinal tract released by specific nutrient intake. The other is also sensitive to nutrient intake, but importantly modulated by relative adiposity. We present evidence to suggest that insulin serves as the key feedback signal to the central nervous system to serve this second function (body adiposity signal). Insulin has been found in cerebrospinal fluid where its concentration is increased by systemic infusions of glucose or insulin and is proportional to its concentration in plasma. When insulin (10 and 100 μU/kg/day) is infused into the lateral cerebral ventricles of free feeding baboons a dose dependent suppression of food intake and body weight is found. Intravenous infusion of 25% and 50% of total calories as glucose elevates endogenous insulin concentrations and suppresses food intake. These findings suggest that the amount of insulin secreted per day and more modulates food intake to maintain a constant body weight.
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 21 (1981), S. 51-53 
    ISSN: 1432-0428
    Keywords: Insulin ; crystal ; dissolution ; bicarbonate ; pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Insulin is insoluble in water at physiological pH, but dissolves relatively rapidly in plasma. To quantify the ability of various solutions to dissolve crystalline insulin, a simple assay measuring dissolution time was developed. At pH 7.5 and room temperature, distilled water, 0.154 mol/l NaCl, Ringer's lactate solution, and 5% albumin in 0.154 mol/l NaCl did not dissolve insulin crystals within 30 min. Normal postprandial human plasma and a protein-free cell culture medium dissolved insulin crystals within 3 to 8 min. This ability was inhibited by acid titration of the fluids to a stable pH of 6.30, at which point bicarbonate depletion could be implied. Repletion of bicarbonate did restore the ability of these solutions to dissolve insulin crystals, but back-titration to the initial pH with NaOH did not. The effect of sodium bicarbonate alone was strongly concentration dependent above 23 mmol/l. We suggest that the ability of physiological fluids to dissolve insulin crystals at normal pH depends on their bicarbonate content. The ability to dissolve insulin with a physiological solvent which prevents its raggregation promises to facilitate its use in portable pumping systems.
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 20 (1981), S. 155-158 
    ISSN: 1432-0428
    Keywords: Insulin ; smooth muscle cells ; atherosclerosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of insulin (10–10000 mU/l) on the proliferation of cultured human arterial smooth muscle cells was studied. Smooth muscle cells were cultivated by explantation. Cells from the third to the fifth subculture were used. Proliferation was studied by growth curve experiments. Insulin stimulated cell proliferation in all concentrations (p 〈0.001). Growth was however stimulated more by a medium containing 10% fetal calf serum. The highest concentration of insulin produced only 35% of the effect of 10% fetal calf serum. Our results support the hypothesis that insulin may play a role in atherosclerosis.
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 425-430 
    ISSN: 1432-0827
    Keywords: Bone induction ; Insulin ; Chondrogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary The influence of somatostatin on discrete stages of collagenous-matrix-induced endochondral bone formation has been investigated. Local injection of somatostatin, i.e., without any measurable systemic effect, resulted in a 75% reduction of cell proliferation as measured by [3H]thymidine incorporation and ornithine decarboxylase activities. The minimum effective inhibitory dose of somatostatin was 0.25 µg/day. Twice daily local injections of the hormone during cartilage formation also resulted in an inhibition, but this was shown to be due to impaired cell proliferation rather than to a direct effect of somatostatin on differentiation. Injection of somatostatin into developing bone tissue after the cartilage stage impaired osteogenesis, assessed by45Ca incorporation and alkaline phosphatase activity. Concurrent injections of insulin and somatostatin obliterated the inhibitory effect of the latter on cell proliferation. Somatostatin can locally regulate the proliferation and differentiation of chondroprogenitor and osteoprogenitor cells in vivo and may directly contribute to the regulation of bone growth by its ability to counteract the stimulatory effect of insulin.
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  • 16
    ISSN: 1432-2013
    Keywords: Cold exposure ; Glucagon ; cycloAMP ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of acute cold exposure on the concentration of glucagon in the blood was investigated in man and in intact and adrenalectomized rats. In man fasted overnight acute cold exposure, which caused a twofold increase in O2-consumption resulted in a rapid rise in plasma glucagon. The levels of insulin and blood glucose remained unaltered, while the concentration of serum free fatty acids and β-hydroxybutyrate increased. In fasted intact rats acute cold exposure lead to similar effects. A close parallelism between the rise in plasma glucagon and the concentration of hepatic cycloAMP was observed. Adrenalectomy did not impair the cold induced rise in plasma glucagon and hepatic cycloAMP. It is concluded that acute cold exposure caused a rapid rise in the concentration of plasma glucagon leading to an increase in the concentration of hepatic cycloAMP, thus enhancing the rate of hepatic gluconeogenesis and ketogenesis. As these alterations were similar in the absence of glucocorticoids and medulla-derived catecholamines, it is suggested that glucagon may play a role in the metabolic adaptation to acute cold exposure.
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  • 17
    ISSN: 1432-5233
    Keywords: Arginine stimulation ; Calcium antagonism ; Glucagon ; Glucose ; Glucose stimulation ; Insulin ; Verapamil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present investigation was designed to evaluate the effect of acute and protracted verapamil administration on insulin and glucagon secretion in man. For this purpose, 14 normal subjects received two consecutive glucose pulses (5 g i.v. in less than 20 sec or 20 g i.v. in less than 1 min, 7 subjects for each group), 70 or 90 min apart, before and during an infusion of verapamil (160 μg/min). Seven additional normal subjects received two consecutive arginine pulses (5 g i.v.), 70 min apart. In 14 inpatients with coronary heart disease, we investigated the effect of protracted verapamil administration. Seven of these subjects underwent two oral glucose tolerance tests (100 g) and the other 7 two arginine tests (30 g) before and after a 10-day treatment with verapamil, 240 mg/die p.o. divided into three doses; the last dose, 80 mg, was given orally 1 h before the performance of the post-treatment test. Verapamil significantly inhibited the acute insulin response (AIR, mean change from 3–10 min) to glucose (5 g), as well as the AIR and AGR (acute glucagon response) to arginine (5 g). By contrast, verapamil failed to alter significantly the AIR to the higher glucose pulse. There was no significant change of oral glucose tolerance after verapamil, nor was there a change in insulin response to oral glucose. By contrast, insulin and glucagon responses to arginine infusion were significantly reduced by the drug.
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Acta diabetologica 18 (1981), S. 123-128 
    ISSN: 1432-5233
    Keywords: C-peptide ; Free fatty acids ; Growth hormone ; Insulin ; Keto-acidosis ; Non-ketotic hyperosmolar diabetic coma ; Tolbutamide test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary For further evaluation of B-cell secretion in diabetic keto-acidosis (KA) and in non-ketotic hyperosmolar coma (NKHC), basal and post-i.v. tolbutamide blood CPR and IRI values were measured in 34 patients (22 KA and 12 NKHC). FFA, cortisol and HGH measurements were also performed. IRI was low in both KA and NKHC (0.07±0.01 and 0.082±0.01 nmol/l) as opposed to CPR which was significantly higher in NKHC (1.14±0.1 nmol/l) than in KA (0.21±0.03 nmol/l). After tolbutamide injection, CPR and IRI levels did not change in any of the KA cases, whereas they significantly increased in half of the NKHC cases. Cortisol and FFA values were similarly increased in both situations, as opposed to HGH which was significantly higher (6.1±1.2 ng/ml) in KA than in NKHC (1.9±0.2 ng/ml). These results suggest that B-cell function is less deficient in NKHC than in KA. Residual insulin amounts reaching the liver via the portal vein could partly account for the absence of ketosis in NKHC.
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  • 19
    ISSN: 1432-5233
    Keywords: Fractional catabolic rate of endogenous triglycerides ; Free fatty acids (FFA) ; Glucose ; Insulin ; Triglycerides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In non-diabetic persons whose serum triglyceride (TG) concentrations ranged from normal to very high levels, endogenous TG turnover was measured using the radioglycerol method of Farquhar and coworkers. Insulin, FFA, and glucose concentrations were estimated during an oral glucose tolerance test. Stimulated insulin levels were correlated positively to TG concentrations and absolute TG turnover rates, and negatively to fractional TG catabolic rates. FFA concentrations had similar relationships, also in non-insulin-dependent diabetics. A more detailed analysis showed that elevated insulin and FFA levels — as an expression of peripheral insulin resistance — are a typical finding in the kind of patients whose fractional TG catabolic rate is low [≤0.210 (h−1)], irrespective of actual serum TG concentration. Our data do not suggest a stimulatory role of insulin for TG production.
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  • 20
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    Springer
    Acta diabetologica 18 (1981), S. 269-272 
    ISSN: 1432-5233
    Keywords: Acid phosphatase ; Cathepsin B ; Insulin ; Isolated islets ; Proinsulin ; Rhamnose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary L-Rhamnose at different concentrations stimulated incorporation of3H-leucine both into islet (pro)insulin and that released into the medium. Maximum isotope incorporation with either glucose or rhamnose was seen at a concentration of 16.7 mM, although the glucose-induced effect was significantly greater. Like glucose, rhamnose also enhanced the activities of acid phosphatase and cathepsin B in isolated rat islets.
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  • 21
    ISSN: 1432-5233
    Keywords: Free fatty acids ; Glucagon ; Indomethacin ; Insulin ; Meal tolerance test ; Normal subjects ; Prostaglandins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have investigated the influence of a single oral administration of indomethacin on blood glucose, plasma free fatty acids (FFA), α-amino-nitrogen, insulin and glucagon concentrations in young healthy subjects. Two groups of 6 subjects were studied, the first received a standardized 500 kcal mixed meal without any previous drug administration (controls) whereas the second group received 50 mg indomethacin 2 h before ingesting an identical meal. Plasma indomethacin concentration reached its maximum (2.36±0.36 Μg/ml) 15 min after administration and declined to 0.45±0.04 ug/ml after 2 h. Indomethacin ingestion was followed by a significant increase in blood glucose and plasma FFA reaching their maximum value at 45 min and returning to basal levels at 120 min. No simultaneous changes in plasma α-amino-nitrogen, insulin or glucagon levels were detected during this period. The meal was followed by a rise in blood glucose and plasma insulin as well as by a decrease in plasma FFA concentration. No significant differences were detected between the controls and the subjects receiving indomethacin. In controls, the meal was followed by a rise in plasma α-amino-nitrogen and a modest although significant increase in glucagon levels. In indomethacin-treated subjects, the increment of α-amino-nitrogen was less marked and the increase in plasma glucagon was not observed. Thus, indomethacin by itself can exert several metabolic effects; however, it does not deteriorate the blood glucose or insulin profile after a regular meal. The present work is the first to demonstrate that an inhibitor of prostaglandin synthesis inhibits the plasma glucagon rise occurring after a physiological stimulus such as a normal meal. On the basis of previousin vitro experiments, we suggest that this effect results from an inhibition of glucagon secretion by the PG synthesis inhibitor.
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  • 22
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    Acta diabetologica 18 (1981), S. 297-310 
    ISSN: 1432-5233
    Keywords: Cyclic AMP ; Cyclic GMP ; Cyclic nucleotides ; Glucose ; Glycogen ; Glycogen synthase ; Insulin ; Rat liver
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To determine if cGMP might function as a second messenger for insulin, anin situ liver perfusion system was established in which hepatic effects of insulin could be correlated with changes in cyclic nucleotides. Several combinations of insulin (10 mU/ml) and glucose (50 mg/ml) were infused (0.1 ml/min) for 30 min into fasted normal and diabetic rats with removal of a similar volume of blood. Samples of livers were removed at the beginning and end and at various times during the perfusion. In normal animals perfused with buffer alone, hepatic glycogen content fell. When glucose (with or without added insulin) was added to the perfusate, glycogen levels rose. With buffer alone, there was no change in the independent (I) form of glycogen synthase at 10 min but a modest increase at 30 min. With insulin and/or glucose, there was a large increase in the I-form of the enzyme at 10 min and a further rise at 30 min. Neither cGMP nor cAMP changed even though tissue samples were obtained at multiple times throughout the perfusion. Cyclic nucleotides were also measured in liver slices exposed to insulin (1 mU/ml) after 30 min of preincubation for stabilization. Although significant increases in cGMP were noted in the tissue exposed to insulin, similar significant rises also occurred in appropriately paired control slices. When glucagon was used in both thein situ perfusion and the paired liver slice systems, the expected rapid and large increases in cAMP levels occurred attesting to the validity of both approaches in evaluating hepatic cyclic nucleotide responses. These results plus the paucity of convincing data in the literature strongly suggest that cGMP can no longer be considered a candidate for the putative second messenger of insulin.
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  • 23
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    European journal of applied physiology 46 (1981), S. 249-259 
    ISSN: 1439-6327
    Keywords: Cold ; Glucose ; Insulin ; Glucagon ; Somatostatin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The role of the endocrine pancreas in glucose production (Ra), utilization (Rd), and metabolic clearance (R'd) was investigated during acute exposure to cold in normal normothermic dogs. Two ambient temperatures (TaN=+25
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  • 24
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    Langenbeck's archives of surgery 355 (1981), S. 648-648 
    ISSN: 1435-2451
    Keywords: Resection ; Insulin ; Glucagon ; Somatostatin ; Magenresektion ; Somatostatin ; Glucagon ; Insulin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung In einer tierexperimentellen Untersuchungsreihe wurde die Freisetzungskinetik der insulären Hormone Insulin und Glucagon und die peripheren Somatostatinspiegel nach Magenresektion mit unterschiedlichen gastroduodenalen und gastrojejunalen Anastomosierungstechniken untersucht. Die Insulinfreisetzung nach distaler Magenresektion mit gastrojejunaler Anastomose unterscheidet sich quantitativ aber nicht qualitativ von den nichtoperierten Kontrolltieren. Glucagon wird nach Ausschluß des Duodenums aus der Nahrungsmittelpassage inadäquat freigesetzt. Periphere Somatostatinwerte waren postprandial nur bei erhaltener Duodenalpassage meßbar.
    Notes: Summary Regulation of the endocrine pancreas receives important impulses from the duodenum and the upper gastrointestinal tract. Insulin release after distal stomach resection with gastrojejunal anastomoses shows quantitative, but no qualitative difference compared to that of the controls. The release pattern of glucagon after elimination of the duodenum from the digestive passage shows a low peripherial increase. After excluding duodenal passage, somatostatin shows a partial lack of peripherially measurable values.
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  • 25
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 26
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The isotope partition coefficient α between cyclohexane, cycloheptane and hydrogen has been determined between 80 and 180° and pressures around 1 atm. The values decrease with increasing deuterium content y of the hydrogen and can be expressed by the simple equation Ina = Δ S/R + (ΔH + δ · y)/RT with an error of ±1%. However it was not possible to achieve good agreement with theoretical calculations using a unique average value for the partition function of the hydrocarbon.
    Additional Material: 1 Ill.
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  • 27
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of reactions of p-chlorobenzenediazonium ions in aqueous buffer solutions (pH 9.0-10.6) under N2 (〈 5 ppb of O2) have been measured between 20 and 50°C. The formation of trans-diazotate is first-order with respect to the concentration of hydroxyl ions and to the equilibrium concentration of diazonium ions, if the diazonium ion⇄cis-diazotate equilibrium is considered as a fast prior equilibrium. This indicates that the p-chlorobenzenediazonium ion, in contrast to all previous investigations with the p-nitrobenzenediazonium ion and benzenediazonium ions carrying similar substituents with a -M effect, rearranges from the cis- to the trans-configuration as diazohydroxide and not as diazotate. The formation of trans-diazotate is catalyzed by carbonate and inhibited by hydrogen carbonate ions; mechanisms of these catalyses are discussed, and the solvent isotope effect KH2O/KD2O measured by an 1H-NMR. technique reported. The kinetics of the dediazoniations can be analyzed as a mixture of two reactions, a relatively fast first reaction, reaction A, which is responsible for about 5% of the total reaction, and a second reaction F. Both are first-order with respect to diazonium ion; reaction A is also first-order in hydroxyl ions. There are some indications that reaction A corresponds to the hydrolysis of the diazonium ion to give eventually amine and nitrite ions. Reaction F shows a complex dependence on hydroxyl ions; it is related to the homolytic dediazoniation.
    Additional Material: 10 Ill.
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  • 28
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 23Na-chemical shifts for the NaClO4 solute depend markedly upon the composition of binary solvent mixtures of THF with amines (pyridine, piperidine, pyrrolidine, aniline, propylamine, and isopropylamine). These changes, analyzed in a novel application of the Hill formalism, show equality of the intrinsic equilibrium constant K for the successive steps, upon displacement of THF from sodium coordination by one of these amines. The results, which are entirely consistent with tetracoordination of the sodium cation by these solvents, also indicate proportionality of the K values to the amine chemical shifts.
    Additional Material: 3 Ill.
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  • 29
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    Helvetica Chimica Acta 64 (1981), S. 568-571 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Phenylglycine esters react with pyruvic acid to give α-methylsuccinic amides 9 instead of the expected Schiff bases 8, analogously to p-anisidine but unlike aniline.
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  • 30
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compounds have been isolated and their structures determined by X-ray crystallography. Their relative stability is discussed in terms of theory and experiment. The endo-adduct is the thermodynamically more stable one.
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  • 31
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    Helvetica Chimica Acta 64 (1981), S. 572-578 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Notes on the Synthesis of Sulfonated Derivatives of 5,6,7,8-Tetrahydro-1-naphthylamine and 5,6,7,8-Tetrahydro-2-naphthylamineSulfonation of 5,6,7,8-tetrahydro-1-naphthylamine (1) with sulfuric acid gave a mixture of 1-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid (2), 4-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid (13) and 4-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid (3). The same reaction with 5,6,7,8-tetrahydro-2-naphthylamine (20) yielded 3-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid (21); formation of 2-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid (16) or of 3-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid (24) was not observed. Treatment of 4-bromo-5,6,7,8-tetrahydro-1-naphthylamine (4) or of its 4-chloro analogue 5 with amidosulfuric acid gave 1-amino-4-bromo-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid (9) and its 4-chloro analogue 10, respectively, which were dehalogenated to 2. Preparations of 13 and 24 were achieved by sulfonation of 5-nitro-1,2,3,4-tetrahydronaphthalene (14) and 6-nitro-1,2,3,4-tetrahydronaphthalene (22) to 4-nitro-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid (15) and 3-nitro-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid (23), respectively, followed by Béchamp reductions. The sulfonic acid 13 was also obtained by hydrogenolysis of 4-amino-1-bromo-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid (11) or of its 1-chloro analogue 12; compounds 11 and 12 were synthesized from N-(4-bromo-5,6,7,8-tetrahydro-1-naphthyl)acetamide (7) and from its 4-chloro analogue 8, respectively, by sulfonation with oleum and subsequent hydrolysis. By ‘baking’ the hydrogensulfate salt of 1 or 20 compounds 3 and 21 were obtained, respectively. Synthesis of 16 was achieved by sulfur dioxide treatment of the diazonium chloride derived from 2-nitro-5,6,7,8-tetrahydro-1-naphthylamine (17) giving 2-nitro-5,6,7,8-tetrahydronaphthalene-1-sulfonyl chloride (18), followed by hydrolysis of 18 to the corresponding sulfonic acid 19 and final reduction.
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  • 32
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    Helvetica Chimica Acta 64 (1981), S. 1023-1025 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Deprotonation of ethyl (E)-2-alkenoates 1, 3 and 4 yields after protonation the double bond migrated (3 Z)-isomers 5, 7 and 9 as major products. In contrast, deprotonation and reprotonation of ethyl (Z)-2-pentenoate (2) gives the (3 E)-isomer 6 exclusively. These findings are explained by reaction paths starting from different ester conformations.
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  • 33
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    Helvetica Chimica Acta 64 (1981), S. 1026-1031 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A New Route to 1, 3-Dicarbonyl Derivatives, Model Investigations on the A/B-Part of-3-Oxo-5α-steroidsStarting from 1 the 1, 3-dicarbonyl compounds 4a-d were synthetized via the enynes 2a-e and the relatively unstable epoxides 3a-d. The latter were reacted with 95% formic acid to gave 4a-d; small amounts of the furane derivatives 5a-c were identified as by-products in this last step. In the presence of catalytic amounts of HgSO4 the epoxides 3a-c yielded with 95% formic acid the furanes 5a-c, but no detectable amounts of 4a-c.
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  • 34
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 1032-1039 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It was found that analysis of the 1H-NMR. signals (at 360 (preferably) and/or 100 MHz) of the protons at C (4) and of the equatorial α-proton at C (6), particularly when these are located in the 2-3 ppm region and therefore convenient for detection and identification, may be of valuable aid in the structural and configurational characterization of 5-hydroxy- and 5-acetoxy-steroids (unsubstituted or containing a hydroxy or acyloxy substituent at C (3)).
    Additional Material: 1 Tab.
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  • 35
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heterodiamantanes and Structurally Related Compounds. Part III. The Pentacyclic C11-Diethers 5, 13-Dioxapentacyclo [6.5.0.02,6.03,12.04,9]tridecane, 4, 13-Dioxapentacyclo [6.4.1.02,7.03,10.05,9]tridecane, and 3, 10-Dioxapentacyclo [7.3.1.02,7.04,12.06,11]tridecaneIn connection with the studies on heterodiamantanes and structurally related compounds the three novel pentacyclic diethers 3-5 were prepared starting from the cyclopentadienone dimer 6. All four compounds have as common features a central carbocyclic 6-membered ring with four axial alkyl substituents and two oxygen functions in 1, 4 position. The required eleventh C-atom was introduced by dichlorocarbene addition either to 6 ( → 7) (Scheme 2) or to 29 ( → 28) (Scheme 4).Diether 3 was obtained by reduction of 26 (Scheme 2), a suitable precursor prepared either by intramolecular addition (24 → 26; Scheme 2) or substitution (30 → 26, 31 → 26; Scheme 4), as well as by direct substitution (44 → 3, 42 → 3; Scheme 5). Diether 4 was the product of a direct substitution (39 → 4, 36 → 4; Scheme 5). The synthesis of diether 5 was achieved from the addition product 51 (resulting from the alcohols 47 and 48; Scheme 6).Diether 4 is the thermodynamically least stable of the three diethers 3-5. It was easily isomerized to 5 on treatment with concentrated sulfuric acid in benzene whereas 3 and 5 remained unchanged under these conditions.
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  • 36
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    Helvetica Chimica Acta 64 (1981), S. 1040-1057 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Spherical Cryptates. Synthesis and Inclusion-Complexes of Spherical Macrotricyclic LigandsA general strategy for the synthesis of spherical macrotricyclic ligands has been developed. Four spherical cryptands, SC-24, SC-25, SC-26 and SC-27 have been obtained by this route. The synthesis and cation-complexing properties of these compounds are described in detail. Stability constants and cation exchange rates of the spherical cryptates obtained with alkali and alkaline-earth cations have been determined. Highly stable complexes are formed by SC-24; the Rb+ and Cs+ cryptates of SC-24 are the most stable complexes of these cations known to date. The size of the intramolecular cavity affects the complexation selectivity. The cation exchange rates are very slow, and the corresponding free energies of activation are even larger than, for macrobicyclic cryptates of similar stability. Both the high complex stabilities and the high activation energies required for cation exchange indicate a marked ‘spherical cryptate effect’ resulting from the highly connected nature of the molecular architecture of spherical macrotricyclic ligands.
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  • 37
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    Helvetica Chimica Acta 64 (1981), S. 1058-1062 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rates of proton transfer from 2, 4-hexadiene, 1, 3-cycloheptadiene, cyclopentadiene and acetone to t-butoxide have been measured in the gas phase using pulsed-ion-cyclotron-resonance spectroscopy. The rate constants are (units of 10-10 cm3 molecule-1 s-1): 2.7 ± 0.4, 3.8 ± 0.4, 6.1 ± 0.7 and 10.8 ± 1.5, respectively. These results are analyzed in terms of the properties of the encounter complex and reaction transition states. The reaction profile for t-butoxide + cyclopentadiene is modeled using RRKM theory and an estimate for the central barrier height is obtained.
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  • 38
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of 2- and 3-Phenyl Substituted Alkylalkylidene Iminium Ions in the Gas PhaseThe collision-induced fragmentations of 2- and 3-phenyl substituted alkylalkylidene iminium ions are reported. Besides the homolytic cleavage of the azaallyl bond a nucleophilic attack of the unsubstituted phenyl group at the iminium function is observed in the gas phase, yielding carbonium ions such as cyclopropanspirobenzenium (3), indanylium (10) and indenylium ions (11).
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  • 39
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A modification of a previously reported synthesis of zeaxanthin (1), and routes to both zeaxanthin and rhodoxanthin (2) from α-ionone, are described.
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  • 40
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transition metal complexes often have low-lying excited electronic states and, as a consequence, tend to be electronically labile, i.e., their electronic properties exhibit pronounced sensitivity to external perturbations. Often drastic changes in various spectroscopic properties indicating substantial electronic rearrangements can be induced be relatively weak intermolecular forces as provided by nonpolar solvents or solid molecular host lattices. This behaviour can be explained by crossing of potential surfaces in the vicinity of the absolute minimum. Many physical properties of a given orbitally (near-) degenerate system depend strongly on the relative magnitude of some characteristic parameters determining the shape of the ground Born-Oppenheimer potential surface(s), e.g. barrier height versus zero-point energy, distance between minima versus zero-point amplitude, energy difference between minima, etc. Typical examples are systems exhibiting Jahn-Teller activity, spin-crossover, mixed valence, exchange coupling and other types of electronic near-degeneracies. In paramagnetic systems changes in the electronic wavefunction can be most conveniently detected and analyzed by using EPR. spectroscopy.In paramagnetic sandwich complexes we studied two types of orbital degeneracies: Jahn-Teller degeneracies (d7-systems such as Co (cp)2, Ni(cp)2+ and Fe (cp) (bz), low-spin d5-systems such as Mn (cp)2) and low-spin/high-spin equilibria (d5-systems such as Mn (cp)2). By diluting these complexes and ring-substituted derivatives in a large variety of diamagnetic host systems we have been able to control the 6A/2E equilibrium of Mn (cp)2 by influencing the metal-to-ring distance and by changing the degree of ring alkylation; similarly we have been able to vary the relative weights of the two electronic states contributing to the two-fold degenerate electronic ground state of d5- and d7-systems to a large degree by variation of the local asymmetric fields offered by the lattice sites of the host systems.For comparison the electronic ground state properties of octahedral Cu(II) complexes with CuN6 CuO6 chromophores, of V (CO)6 and tetrahedral VCl4 were also studied by EPR. between 4K and room temperature in several host systems. Characteristic differences in the details of the temperature and host dependence of the EPR. spectra in all these electronically labile systems can be explained in terms of differences in the vibronic coupling type (E ⊗ e vs. T ⊗ e, t), the strength of linear and/or quadratic JT-coupling and the effects produced by spin-orbit coupling.
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  • 41
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Structure of Porphine-type Nickel Complexes Containing Axially Oriented SidechainsThe structure of (±)-[1, 11-dimethoxy-10 H-HDP (2-)]nickel (3), the product of the thermodynamically controlled addition of methanol to [6 H-HDP]nickel-bis-(tetrafluoroborate) (1), was determined by X-ray analysis. The two methoxy groups in 3 are cis-oriented. The syntheses and spectroscopic properties of [1, 11-diethoxy-10 H-HDP (2-)]nickel (5), [1, 11-dineopentyloxy-10 H-HDP (2-)]nickel (6) as well as the bridged complexes [1, 11-pentamethylenedioxy-10 H-HDP (2-)]nickel (4) and [1, 11-(E)-2,3-(dimethyl-2-butenylenedioxy)-10 H-HDP (2-)]nickel (7) are described. Reaction of 1 with bromide ions or 4-methylpyridine leads to the formation of the corresponding hexacoordinated, paramagnetic complexes dibromo [6 H-HDP]-nickel (II) (8) and bis (4-methylpyridine)[6 H-HDP]nickel-bis (tetrafluoroborate) (9).
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  • 42
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We describe a flexible, stereocontrolled synthesis of enantiomerically pure substituted cyclopentenes and cyclopentanes - including 11α-hydroxy-13-oxaprostanoic acid 20 - (-)-quinic acid via an acyclic precursor 6 by an intramolecular aldolisation-dehydration reaction.
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  • 43
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Absolute conformation of 7-chloro-5-phenyl-1-[(S)-α-phenylethyl]-1, 3-dihydro-2H-1, 4-benzodiazepin-2-one (1c) in crystal, and its inversion rate in solution were determined, enabling prognosis of direction of asymmetric induction during C(3)-alkylation.
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  • 44
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Application of the α-Alkynone Cyclization: Synthesis of rac-Modhephenerac-Modhephene 1, the first sesquiterpene with a propellane C-skeleton and its epimer rac-epi-modhephene 27, were synthesized starting from bicyclo[3.3.0]oct-1(5)-en-2-one (2). The key step in the construction of the [3.3.3]-propellane system is an application of the α-alkynone cyclization, namely 3 → 4 and 11 → 14. The preferred formation of the propellanes 4 and 14 in this step shows that the insertion of the postulated alkylidene carbene intermediate into tertiary C,H-bonds outweighs the one into the secondary ring-C,H-bonds leading to 12/13 and 15/16, respectively. The two starting materials for the α-alkynone cyclization, 3 and 11, were prepared from 2 by the reactions shown in Scheme 3. The further elaboration and separation of the cyclization products 4 and 14 to rac-modhephene 1 and its epimer 27 are outlined in Scheme 5.
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  • 45
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    Helvetica Chimica Acta 64 (1981), S. 389-398 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transformations of 13 alcohols and 13 diols in the presence of a small amount dimethylsulfoxide (1/16 mol) were studied. Relationships were found between the type of the hydroxy compound and the selectivity of the transformation, and conclusions were drawn regarding the transformation mechanism. The ether formation observed with certain alcohols proceeds via a carbenium cation. The reaction conditions applied were found suitable for inducing water elimination from the ditertiary 1,2- and 1,3-diols (pinacol rearrangement, 1,2-elimination). From the 1,4- and 1,5-diols the corresponding oxacycloalkanes can be obtained in good yield. Cyclodehydration occurs by intramolecular nucleophilic substitution, via a concerted mechanism. The effect of DMSO is exerted directly, and protoncatalysis occurs simultaneously.
    Additional Material: 2 Ill.
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  • 46
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    Helvetica Chimica Acta 64 (1981), S. 425-429 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Novel Example of Unsaturated Branched-chain Sugar Nucleoside: 3′-Deoxy-3′-methylidene-adenosineStarting from 5-O-benzoyl-3-C-methylidene-3-deoxy-1,2-O-isopropylidene-α-D-erythro-pentofuranose (11) the title compound 8 has been prepared. Its α-anomer (9) and the acyclic sugar nucleoside 10 have been obtained as by-products. Adenosine deaminase slowly deaminated 8, 9 being not affected. Compound 8 exhibited no antiviral activity, whereas one of its saturated analogues (13) inhibited the multiplication of the herpes-1 (HF) virus.
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  • 47
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 449-457 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The configurational isomers of astaxanthin (3,3′-dihydroxy-β,β-carotene-4,4′-dione) from the flesh of salmon (Salmo salar and Oncorhynchus) caught at different places in Europe and Canada were isolated and analyzed as (-)-camphanic acid diesters by means of HPLC. The biological variation in the composition of the configurational isomers in seven fish was surprisingly similar: 78 to 85% of (3S, 3′S)-astaxanthin, 12 to 17% (3R, 3′R)-astaxanthin and 2 to 6% meso-astaxanthin.
    Additional Material: 5 Ill.
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  • 48
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An interactive system of programs has been developed to assist in structure elucidation based on mass spectral data. The program relies on algorithms for generating all the structural isomers that constitute alternative explanations of the observed data and it associates relative plausibility values with the different isomers. The structure assembly part of the program allows for the use of overlapping substructural components, such as substructures inferred from the appearance of particular ion patterns in the spectrum of an unknown compound. Mass spectrum interpretation procedures used with this structure assembly process could exploit any form of spectrum-substructure correlation scheme. In this work, the emphasis has been on the use of detailed and class specific spectrum-substructure correlations. Applications of the program are illustrated by means of an example analysis of the mass spectra of a variety of marine sterols.
    Additional Material: 4 Tab.
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  • 49
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selective Modification of the Terminal Amide Group of Linear Polyamides via 2-Oxazolin-5-ones as IntermediatesTreatment of aqueous or alcoholic solutions of diamides of type 2 with HCl leads to the formation of amide-acids and amide-esters of type 3 (Scheme 1 and Table). It has been shown, that 2-oxazolin-5-ones of type 4 are intermediates of this selective transformation of the disubstituted terminal amide group. The selectivity of the transformation is demonstrated by the reaction sequence shown in Scheme 3. No selectivity has been observed in the acid-catalyzed hydrolysis of triamide 9 with a monosubstituted terminal amide group (Scheme 4). Hydrolysis of the optically active dipeptide derivatives (+)-(L)-13 and (+)-(L)-15 with HBr in nitromethane at 60-80° yields the pure enantiomer (+)-(L)-14 and (+)-(L)-16, respectively (Scheme 5), i.e., no racemization takes place under the reaction conditions.These results show the usefulness of the dimethylamide group as a protecting group for carboxylic acids for example in the peptide synthesis.
    Additional Material: 2 Tab.
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  • 50
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 15N-CIDNP. spectra recorded during the reaction of diazonium cations with OH- in weakly alkaline aqueous solutions show that the dediazoniation is at least partially homolytic. The polarizations observed for the diazonium and trans-diazotate ions can be explained by reaction proceeding via a cage involving diazenyl and diazotate radicals using Kaptein's rules and simple intensity considerations.
    Additional Material: 2 Ill.
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  • 51
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of dediazoniation of p-chlorobenzenediazonium tetrafluoroborate have been studied in buffer solutions in the pH-range 9.0-10.0, ionic strength I = 0.10, at 20.0° in glass and polytetrafluoroethylene vessels. The presence of oxygen (〈5 ppb of O2, 60 to 100 ppb of O2, air, 〉 99% of O2) has a decisive influence on the rate and kinetic order of the dediazoniation. Iodoacetic acid inhibits the reaction, whereas p-chlorophenol has a catalytic effect, and in air and 〉99% of O2 it acts as an autocatalyst. The reaction is subject to general-base catalysis by water, hydroxyl ions, hydrogen carbonate and carbonate ions. The kinetic results are interpreted in conjunction with data concerning the reaction products [2] and a 15N-CIDNP. investigation of a related system [3]. Specific radical chain mechanisms are consistent with the results.
    Additional Material: 10 Ill.
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  • 52
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The product distribution of compounds 2, 3 and 4 formed in the electrohydrodimerization (EHD) of 1 was determined as function of the water content of the solvent (CH3CN). The presence of water favours the formation of the glycols 4 and reduces the relative amounts of 1,6-diketones 2 and hydroxyketones 3, as determined by GC./MS.-analysis.
    Additional Material: 1 Ill.
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  • 53
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    Helvetica Chimica Acta 64 (1981), S. 1575-1578 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The unusual propellane skeleton of the sesquiterpene modhephene (1) has been synthesized starting from cyclopentenone (2). The key step 6 → 7 is an efficient and highly stereoselective intramolecular thermal ene-reaction. Further elaboration of the propellane 7 gave the enone 10 which had been previously converted to (±)-modhephene (1) in three steps.
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  • 54
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the present work a mixing-reaction model is developed to describe the influence of the space- and time-dependent concentration of the leaving group on the pre-equilibria of the reactants and thus on the product distribution of mixing-disguised reactions. The modelling is carried out using a typical example of such reactions, namely azo coupling, where the leaving group is a proton. For this reaction, the existence of characteristic sets of parameters is established, for which the product distribution does not depend on the initial pH-value. These sets of parameters define the isoselectivity points.
    Additional Material: 6 Ill.
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  • 55
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: rac.-Ajmalicine (31) and 19-epi-ajmalicine (30) have been synthesized by a convergent route from the preformed D, E-ring moieties 25 and 27 and tryptophyl bromide. Two syntheses of the trans-1-benzoyl-3-vinyl-4-piperidineacetic acid (13), used in the preparation of 25 and 27, are also described.
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  • 56
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    Helvetica Chimica Acta 64 (1981), S. 1653-1662 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: X-ray Structure Analyses of Chiral Ionophores: The NH4NCS Complex of 9,9′-Spirobifluorene-22-crown-5In the crystalline NH4NCS complex of 9,9′-spirobifluorene-22-crown-5 (1) the NH4+ ion sits in the centre of the polyether ring, with distances of 2.92-3.15 Å to the five O-atoms and shows at least twofold orientational disorder. In one orientation, three H-atoms point toward O-atoms and the fourth to the N-atom of the anion situated 2.78 Å above the polyether ring. In another, only two H-bonds are formed. The mean planes of the two fluorene parts of the molecule are perpendicular to each other.Crystals of 2,2′-bis (hydroxymethyl)-9,9′-spirobifluorene (2), an intermediate for the synthesis of 1, contain occluded benzene, which cannot be removed under vacuum. X-ray analysis shows that the benzene molecule does not interact with the spirobifluorene in a specific way but merely occupies cages in the crystal packing.
    Additional Material: 5 Ill.
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  • 57
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    Helvetica Chimica Acta 64 (1981), S. 1717-1717 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 58
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    Helvetica Chimica Acta 64 (1981) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 59
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    Helvetica Chimica Acta 64 (1981), S. 1717-1727 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The N-diazo coupling of p-chloroaniline with p-chlorobenzenediazonium tetrafluoroborate in acetonitrile at 30° shows non-linear base catalysis by water. The results are interpreted in terms of the SE2 mechanism with rate-limiting proton loss at low base concentration; it is postulated, moreover that the reaction proceeds via transition states in which varying degrees of H-bonding from the amine and the intermediate ω-complex to different water species influence the initial step and the base catalysis.
    Additional Material: 2 Ill.
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  • 60
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nucleotides. XV. Synthesis and Properties of 2′O-t-Butyldimethylsilyl-5′-O-monomethoxytritylribonucleoside-3′-phosphotriesters, Starting Materials for Oligonucleotide SynthesesThe syntheses of two types of fully blocked ribonucleoside 3′-phosphotriesters 6-14 have been achieved in excellent yields from 2′-O-t-butyldimethylsilyl-5′-O-monomethoxytrityl-ribonucleosides 1-5 by phosphorylation with 2-chloro- and 2,5-dichlorophenylphosphorodichloridate respectively and subsequent treatment by cyanoethanol to 6, 8, 10, 12 and 14 and by p-nitrophenylethanol to 7, 9, 11 and 13. These phosphotriesters are valuable starting materials for oligonucleotide syntheses due to the fact that the corresponding phosphotriesters 15-23 with free HO—C(5′) could be obtained by detritylation and the 3′-phosphodiester triethylammonium salts 24-32 by deblocking of the cyanoethyl and the 2,5-dichlorophenyl group respectively. All newly synthesized compounds have been characterized by UV.-and NMR.-spectra as well as C, H, N elementary analyses.
    Additional Material: 4 Tab.
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  • 61
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: XIV. Substituted β-Phenyl-ethyl Groups. New Blocking Groups for Oligonucleotide Syntheses by the Phosphotriester ApproachVarious o- and p-substituted β-phenylethanols (2-10) have been synthesized and investigated as blocking groups in the phosphotriester approach. A large number of 5′-O-tritylated thymidine-3′-phosphotriesters (13-36) with two different phosphate protecting groups have been prepared, characterized, and studied according to their chemical stability and usefullness for oligonucleotide syntheses. The combination of a 5′-O-monomethoxytrityl- and a 3′-(2,5-dichlorophenyl, p-nitrophenylethyl)-phosphate function as in 18 turned out to possess optimal properties as a monomeric nucleotide building block due to the fact that these blocking groups can be quantitatively and selectively be removed without harming each other by trifluoroacetic acid in chloroform to 41, by oximate to 42, and by DBU to 43. The base-catalyzed removal of the monosubstituted phenylethyl groups by DBU or DBN respectively as well as the disubstituted phenylethyl groups by triethylamine in aprotic solvents is a β-elimination process leading to phosphodiesters without attack on the P-center.
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  • 62
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Various free radicals formed during UV.-irradiation of aliphatic dicarboxylic acids in aqueous and methanolic solution are identified by ESR.-spectroscopy. Their structures point to α-cleavage and photoreduction as the dominant primary photochemical decay processes. The relative contributions of these reactions to the overall photodecomposition depend on solvent and degree of α-alkylation of the acid. Emission ESR.-spectra are found for radicals formed by C, CO-bond cleavage of α-dimethyl substituted acids. The polarization is referred to the triplet mechanism of CIDEP. and indicates this cleavage reaction occurs from a triplet molecular state.
    Additional Material: 6 Ill.
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  • 63
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    Helvetica Chimica Acta 64 (1981), S. 1910-1929 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The temperature and solvent dependence of the ESR. spectra of a number of semiquinone- and semidione-type radicals have been investigated with the aim of obtaining structural and kinetic information about intramolecular hydrogen bonding. Systematic variation of the chemical structure of the radicals indicates that in many cases formation and/or exchange of intramolecular H-bonds is disturbed or even precluded by steric hindrance or concomitant dynamic processes, such as internal rotation and/or intermolecular proton exchange.
    Additional Material: 8 Ill.
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  • 64
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    Helvetica Chimica Acta 64 (1981), S. 1943-1948 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, surface activity and micelle formation of three novel cyanine dyes with amphiphilic character is described. It is illustrated by combined surface tension and absorption measurements that in one case self-assembly is highly cooperative leading to aggregates with unique absorption properties.
    Additional Material: 5 Ill.
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  • 65
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    Helvetica Chimica Acta 64 (1981), S. 1964-1967 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Naturally occurring kaempferol 3-O-β-D-(6″-O-coumaroyl)glucopyranoside (tiliroside) has been synthesized thereby confirming its structure. This is the first acylated flavonoid glycoside to be synthesized.
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  • 66
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    Helvetica Chimica Acta 64 (1981), S. 1968-1968 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 67
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Juliprosine, a Further Alkaloid Isolated from Prosopis juliflora A.DC.By catalytic hydrogenation of the second base juliprosine (2) isolated from Prosopis juliflora (Leguminosae) the hexahydroderivative 5 was formed. The same product was obtained also by catalytic hydrogenation of juliprosopine (1) of known structure. The absolute configuration of 2 was deduced by comparison of [M]D values of Prosopis alkaloids of known absolute configuration.
    Additional Material: 1 Tab.
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  • 68
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    Helvetica Chimica Acta 64 (1981), S. 1985-1990 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3,5-Octadiyne cation in its lowest excited state has been studied in the gas phase by laser-induced fluorescence and photoelectron-photon coincidence techniques. The excitation spectrum of the Ã2″←2A″ transition has been obtained and yields vibrational frequencies of some of the fundamentals for the excited cationic state. The fluorescence quantum yields and lifetimes at selected energies within the Ã2A″ state have been determined from the coincidence measurements. This provides quantitative data for the discussion of the relaxation behaviour of such an excited open-shell cation.
    Additional Material: 2 Ill.
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  • 69
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    Helvetica Chimica Acta 64 (1981), S. 2002-2021 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Deprotonation of the 3-trialkylsilyloxy-1,4-diene 3a and subsequent electrophilic substitution of the non-isolated 3-trialkylsilyoxypentadienyllithium 4 gives the α- and γ-products 8 and/or 6 in good yields. Whereas alkylation of 4 proceeds with variable regioselectivity (Table 1) aldehydes and ketones attack preferentially the γ-position of 4 (Table 2). The desired γ-products 6 may be directly subjected to inter- and intramolecular [4 + 2]-additions as demonstrated by the reactions 5a (≡ 6d) → 7 and 6h → 19 (Schemes 4 and 12). Alternatively, smooth fluoride-promoted silylether-cleavage 6 → 11 (Scheme 8) provides a convenient approach to substituted vinyl ketones such as to the natural products 11f (Table 3). The stereoselective conversion 6k → 23 (Scheme 13) implies an endo-selective intramolecular Diels-Alder addition (26 → 23) and exemplifies the use of 4 as an equivalent of the hypothetical anion IV. Furthermore, some electrophilic substitutions of the hexadienyllithium 15 have been studied (Scheme 10).
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  • 70
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    Helvetica Chimica Acta 64 (1981), S. 1937-1942 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Zinctetramethylpyridylporphyrin (ZnTMPyP4+) in acidic aqueous solution sensitizes efficiently oxygen generation by visible light in the presence of acceptors such as Fe3+ - and Ag+-ions and colloidal RuO2/TiO2 redox catalyst. Hydrogen and oxygen are cogenerated under visible light illumination of ZnTMPyP4+ solutions when a bifunctional catalyst (Pt and RuO2 codeposited onto TiO2) is employed.
    Additional Material: 3 Ill.
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  • 71
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Effects of the Nature of the C(1) Substituent on the Conformational Equilibrium of (E)-derivatives of 3-Methoxypropene: Determination of the origin of the phenomenon using energy partitioning techniquesIntermolecular interactions taking place in the compounds of the general formula (E)-CH3OCH2CH=CHX were analyzed in terms of one- and two-center interaction energies within the framework of SCF ab initio (STO-3G), Extended Hückel and CNDO methods. The results confirmed the important role of unoccupied orbitals in the stabilization of the different conformers.
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  • 72
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    Helvetica Chimica Acta 64 (1981), S. 1969-1970 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 73
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    Helvetica Chimica Acta 64 (1981) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 74
    ISSN: 0018-019X
    Keywords: All-trans-retina ; N-butyl-(all-trans-retinylidene)amine ; 1H-NMR. ; l, 13C-NMR. ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Schiff base of all-trans-retinal was investigated in organic solution by 1H- and 13C-NMR. at high field. Complete assignment of the 1H-NMR. peaks of N-butyl-(all-trans-retinylidene)amine (2) and the N-butyl-(all-trans-retinylidene)-ammonium ion (3) was achieved by INDOR (internuclear double resonance). The vicinal proton coupling constants of the polyene chain show that the π-bond orders remain unchanged in N-butyl-(all-trans-retinylidene)amine relative to all-trans-retinal (1), but change towards larger π-delocalization in the N-butyl-(all-trans-retinylidene)ammonium ion. At --61° only one isomer of N-butyl-(all-trans-retinylidene)ammonium was observed. This was shown to be trans at the imine linkage and independent of the solvent. The trifluoroacetic acid counter-ion can approach the positive charge of the N-atom in the weakly polar solvent dichloromethane but not in the leveling solvent methanol. In dichloromethane the nature of the 1:1 complex is a H-bonded (O-…H-N+) ion-pair whose rate of breaking and forming is rapid at RT. Strong stabilization of the ion-pair resulted from homo-conjugation with a second molecule of trifluoroacetic acid. Excess of acid efficiently diminished the isomerization rate at the C,N-bond.
    Additional Material: 6 Ill.
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  • 75
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    Helvetica Chimica Acta 64 (1981), S. 2022-2028 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: γ-Selective sulfenylation of the triethysilyloxypentadienyllithium 1 gave the versatile alkylthiodene 4 which on successive deprotonation and alkylation furnished with high regioselectivity the γ-products 6. Fluoride-promoted silylether cleavage 6 → 7 may be followed by intramolecular [4 + 2]-addition 7c → 8 and sulfoxide elimination 8 → 9. The conversions 7b → 12 and 7a → 17 demonstrate the feasibility of 5 to serve as an equivalent of the hypothetical β-deprotonated divinylketone 13 whose two enone units may be unmasked separately.
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  • 76
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    Helvetica Chimica Acta 64 (1981), S. 2056-2064 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new metabolites have been isolated from cultures of Chaetomium globosum. The structures of 19-O-acetylchaetoglobosin B (4) and 19-O-acetylchaetoglobosin D (5) are assigned. The 13C-NMR. spectra of chaetoglobosin A (1), 19-O-acetylchaetoglobosin A (2), chaetoglobosin C (3), 19-O-acetylchaetoglobosin B (4), 19-O-acetylchaetoglobosin D (5) and of cytochalasin G (6), a (3-indolyl)-[11]cytochalasan isolated from Pseudeurotium zonatum, have been interpreted.
    Additional Material: 2 Ill.
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  • 77
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The products of the thermolysis of N-(1-pyridinio)-2-nitroanilides (1) had previously been interpreted as tris (2-nitrophenyl)-triaziridines (3). The present work shows them to be actually 1, 2-bis[(Z)-(2′-nitrophenyl)-ONN-azoxy]benzenes (5). The revised structural assignment is based on the chemical and the spectroscopic (especially 1H-NMR.) properties of 5 and on the results of a X-ray structural analysis.
    Additional Material: 1 Tab.
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  • 78
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    Helvetica Chimica Acta 64 (1981), S. 2148-2153 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The appearent first-order rate constants for the oxidation of water by iron tris (bipyridyl) (Fe (bpy)3+3), and reduction of water by methylviologen (MV+) catalyzed by a stabilized RuO2 or Pt-sol, respectively, were measured. Rate constants for water oxidation at pH 7 of 0.4 s-1 and water reduction at pH 4.7 and pH 1 of up to 460 s-1 for different sols were found.
    Additional Material: 3 Ill.
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  • 79
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photophysical and electron transfer properties of the lowest excited state of nine ruthenium (polypyridine) complexes have been characterized. The complexes studied are Ru (bpy)3-n (LL)2+n, where n varies from 0 to 3, and LL is 4, 4′-di-t-butyl-2,2′-bipyridine (DTB-bpy), 3, 3′-dimethyl-2, 2′-bipyridine (DM-bpy), or a 2, 2′-diquinolyl derivative (DMCH). The results obtained show that the Ru (bpy)2(DMCH)2+ complex is expected to be a more efficient mediator than Ru (bpy)2+3 in the water-splitting reaction by solar energy.
    Additional Material: 2 Ill.
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  • 80
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 2183-2188 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational behaviour of sulpiride has been investigated by the quantum mechanical PCILO method and by CD. measurements. The results indicate the predominance of a folded, intramolecularly H-bonded conformer, with extended conformers being only slightly less stable. The pharmacological relevance of these results is briefly discussed.
    Additional Material: 3 Ill.
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  • 81
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    Helvetica Chimica Acta 64 (1981), S. 2193-2202 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermolysis of the potassium 2-substituted bicyclo [2.2.2]oct-5-en-2-alkoxides derived from alcohols 2-17 at 90-120° in hexamethylphosphoric triamide affords unsaturated ketones resulting from allylic bond cleavage. The mechanistic and synthetic aspects of this anionic fragmentation are discussed with reference to the formation of 1-(3′-cyclohexenyl)-2-alkanones 18-28 via initial heterolytic C(1), C(2)-bond cleavage in the substrate alkoxide and regioselective, intramolecular protonation of the resultant transient allylic anion.
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  • 82
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 2219-2226 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hitherto unknown diterpenoid 14-hydroxytaxodione (10a) has been prepared by oxidation of 6β-hydroxyroyleanone. Its solutions exhibit a dynamic structural behaviour (UV./VIS/. and NMR.) and lead to an equilibrium mixture of the 11, 14- and the 6, 12-dioxo forms. By methylation and acetylation the 6, 12-dioxo form can be isolated. Chloroform solutions of 14-hydroxytaxodione slowly set up a mixture of coleon V (2a), coleon U (3) and dimeric products (later established as grandidone C, grandidone D and 7-epigrandidone D). Therefore, coleon V (2a) owing to its strong intramolecular H-bond is more stable than 7, 14-dihydroxy-taxodione (2b).
    Additional Material: 1 Ill.
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  • 83
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isolation of 14-Hydroxytaxodione from Plectranthus grandidentatus GÜRKE and of Seven New Dimeric Diterpenoids from P. grandidentatus, P. myrianthus and Coleus carnosus Structures of Grandidone A, 7-Epi-A, B, C, D and 7-Epi-DFrom the leaf-glands of the title plant the following abietane diterpenes have been isolated and their structures established by chemical, spectroscopical and X-ray methods: 14-hydroxytaxodione (5, 0,57%), new as a natural product, the already known coleons U (6, 0,17%) and V (7, 0,024%), and furthermore 7 novel dimeric compounds named grandidones (ca. 0,09%), Both grandidone A (1a) and 7-epigrandidone A (1b) as well as grandidone B (2a) and 7-epigrandidone B (2b) are C(7) acetals of 6, 7-Dioxoroyleanone with catecholes such as coleon U (→ 1a, 1b) or coleon V (→ 2a, 2b). Based on the relative configuration at C(7) of 1a which was established by X-ray analysis, the constitutions of 1b, 2a and 2b were assigned by HPLC. - controlled interconversions. The unstable grandidone C (3) is a C(7)-C(7′) linked bis-6-oxoroyleanone with C2-symmetry. Grandidone D (4a) and 7-epigrandidone D (4b) are spiro-dihydrofurans formed from 3 via a hypothetical bis (14-hydroxytaxodione) by intramolecular addition of HO-C(14) or HO-C(14′) to C(7′) to C(7′) or C(7). The relative configuration of 4a was established by X-ray analysis of its diacetate 4c. The absolute configuration of all dimers was established by the partial syntheses from 14-hydroxytaxodion (5) (entirely described in the following communication).
    Additional Material: 10 Ill.
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  • 84
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Contributions to the Knowledge of the Corrin Chromophore: XII [1]. Chemical Behaviour of the Reaction Product of Heptamethyl Dicyano-cobyrinate with Hypochlorous AcidHeptamethyl chloro-cyano-5α, 10, 15-trichloro-6α, 14-dihydroxy-5,6,14,15-tetrahydrocobyrinate (2) in CH3OH/H2SO4 yields with RuO2 under 50 bar hydrogen and at 100° during 2 h a mixture of heptamethyl dicyanocobyrinate (1) with an epimeric ester. Using deuterium instead of hydrogen in this reaction, C(13) comes out as the probable epimerization center.
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  • 85
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 2251-2256 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Partial Synthesis of Grandidones A, 7-Epi-A, B, 7-Epi-B, C, D and 7-Epi-D, from 14-HydroxytaxodioneOxydative addition of coleon U (6) to 14-hydroxytaxodione (5) in the presence of Fétizon's reagent mainly leads to grandidone A (1a) and 7-epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7-epigrandidone B (2b) (ca. 3:1). Dimerization of 14-hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7-epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7-epigrandidone D (4b) and interconversions of 4a and 4b were achieved.Oxydative addition of coleon U (6) to 14-hydroxytaxodione (5) in the presence of Fétizon's reagent mainly leads to grandidone A (1a) and 7-epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7-epigrandidone B (2b) (ca. 3:1). Dimerization of 14-hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7-epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7-epigrandidone D (4b) and interconversions of 4a and 4b were achieved.Oxydative addition of coleon U (6) to 14-hydroxytaxodione (5) in the presence of Fétizon's reagent mainly leads to grandidone A (1a) and 7-epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7-epigrandidone B (2b) (ca. 3:1). Dimerization of 14-hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7-epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7-epigrandidone D (4b) and interconversions of 4a and 4b were achieved.Oxydative addition of coleon U (6) to 14-hydroxytaxodione (5) in the presence of Fétizon's reagent mainly leads to grandidone A (1a) and 7-epigrandidone A (1b) (ca. 15:1), whereas coleon V (7) and 5 under the same conditions yield grandidone B (2a) and 7-epigrandidone B (2b) (ca. 3:1). Dimerization of 14-hydroxytaxodione (5) gives grandidone C (3; ca. 40%), grandidone D (4a; ca. 50%) and 7-epigrandidone D (4b; ca. 10%). All these compounds obtained by partial synthesis are in every respect identical with the natural products, thus establishing their absolute configurations. The thermal transformation of grandidone C (3) to grandidone D (4a)/7-epigrandidone D (4b) and interconversions of 4a and 4b were achieved.
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  • 86
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Novel Types of C-Glycosyl-derivatives from Acetylenic Sugars or Partial Synthetic Equivalents thereofThe concept of synthetic equivalent is not unequivocal and, for example, α-fluoroenamines may behave in some cases as synthetic equivalents of ynamines and, in other situations, quite differently. Some uses of these α-fluoroenamines, ‘partial synthetic equivalents’ of ynamines, for the synthesis of C-glycosyl derivatives of coumarins, chromones, quinolines, quinolones, thietenes and isoxazoles are described.We also report the preparation of a series of mono- and diglycosylthiophenes by reacting HS- with mono- and diglycosylbutadiynes. Acetylenic sugar derivatives have also been used for the synthesis of a diglycosylazaphosphorine and a spirooxolenone.
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  • 87
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Occurrence of New Bifunctional Esters In Roman Camomile Oil (Anthemis nobilis L.)Some novel aliphatic esters of the unusual 3-hydroxy-2-methylidenebutyric acid have been found in the commercially available essential oil. Additionally, esters of (Z)-2-methyl-2-butenoic acid of structurally similar diols or other bifunctional alcohols have also been identified. Spectral data as well as a synthetic approach to the new esters of 3-hydroxy-2-methylidenebutyric acid are given.
    Additional Material: 4 Ill.
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  • 88
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: CD.-Based Configurational Assignments of GlycosylaziridinesThe relationship between CD.-curves and the configuration of the trans-2-benzoyl-3-phenylaziridines was known. By studying a series of cis- and trans-2-glycosyl-3-benzoylaziridines we have shown that CD. allows the assignment of the configuration at both asymetric C-atoms. As benzoylaziridines can easily be obtained from cyano- or alkoxycarbonylaziridines without configurational change, the absolute configuration of these last two classes of compounds can also be assessed by this method.
    Additional Material: 1 Tab.
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  • 89
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactivity and Electronic Structure of Porphine-type Nickel ComplexesThe electronic structure of the porphine-type hexaaza[16]annulene-nickel dikation 1′ as well as its mono- and diaddition products 2′ and 3′ (Scheme 2) has been considered by an extended Hückel treatment (SCCC-MO including charge iteration on the central metal atom). Correlations between calculated data and reactivity of the porphinoid compounds 1, 2 and 3 (Scheme 1) are discussed.
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  • 90
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    Helvetica Chimica Acta 64 (1981), S. 2378-2382 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: One-bond 13C, 13C-spin-coupling constants have been measured, with natural isotope abundance, in η4-diene, η3-allyl and η2-ene transition-metal carbonyl complexes. Typical values of 1J(C,C) are given for Fe-, Ru- and Os-complexes with the three types of olefinic ligands. The effects of substituents and the structural significance of the C,C-coupling constants are discussed.
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  • 91
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    Helvetica Chimica Acta 64 (1981), S. 2383-2392 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The circular dichroism (CD.) spectra of all-trans-(3S, 3′S) astaxanthin diacetate and its 9-cis, 13-cis, 9,9′-di-cis, 9,13′-di-cis, and 9,13-di-cis isomers conform to the rules previously formulated for optically active carotenoids with a 4-oxo-β-end ring containing an asymmetric C-atom [1]. Thus the CD. bands of the all-trans and the di-cis isomers show the same signs whereas those of the mono-cis isomers have opposite signs. The CD. spectra of all the astaxanthin diacetate isomers invert sign upon cooling to -180°. The CD. spectra of the 9-mono-cis and 9,9′-di-cis isomers and to a lesser extent also those of the 9, 13′-di-cis and 9, 13-di-cis isomers are concentration dependent at -180°, with the longest wavelength band giving at the higher concentration a bisignate CD. curve under the main absorption characteristic of aggregation. This phenomenon has been observed only in isomers with a 9-cis linkage. It is suggested that steric hindrance prevents such aggregation taking place in the other isomers.
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  • 92
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The iridoid and aryl glycosidic constituents of Globularia nudicaulis L. and G. nana LAM. are reported. The structure determination of lytanthosalin (10-O-(E)-cinnamoylaucubin), a new acylated iridoid glucoside, isolated from the latter species, is described.
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  • 93
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Astaxanthin from β-Ionone. I. A Route to the Enantiomeric C15-Wittig Salts by Chemical and Microbial Resolution of (±)-3-Acetoxy-4-oxo-β-iononeRacemic 3-acetoxy-4-oxo-β-ionone (10) was synthesized from the industrially accessible intermediate β-ionone (5). Resolution of 10 into its enantiomers was achieved via the corresponding diastereomeric camphanates and by microbial resolution. Site-selective alkylation of racemic and of optically pure 3-acyloxy-4-oxo-β-ionones with vinyl magnesium chloride at -70° furnished the corresponding 3-acyloxy-4-oxo-9-vinyl-β-ionols which could be transformed to the Wittig salts 1, 3 and 4, respectively, following known procedures [1].
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  • 94
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Technical Procedures for the Synthesis of Carotenoids and Related Compounds from 6-Oxo-isophorone. III. A New Concept for the Synthesis of the Enantiomeric AstaxanthinsA new and efficient concept for the total synthesis of (3S, 3'S)- and (3R, 3'R)-astaxanthin (1a and 1c, resp.) in high overall yield and up to 99,2% enantiomeric purity is described. Key intermediates are the (S)- and (R)-acetals 10 and 17, respectively (Scheme 2). These chiral building blocks were synthesized via three different routes: a) functionalization of the enantiomeric 3-hydroxy-6-oxo-isophorons4) 2 and 11, respectively (Scheme 2); b) optical resolution of 3,4-dihydroxy-compound4) 19 (Scheme 3), and c) fermentative reductions of 6-oxo-isophorone derivatives (Schemes 4 and 5). - The absolute configurations of the two intermediates 12 and 13 (Scheme 2) have been confirmed by X-ray analysis. - The final steps leading to the enantiomeric astaxanthins are identical with those described for optically inactive astaxanthin [1].
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  • 95
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Optically Active Natural Carotenoids and Structurally Related Compounds. IX. Synthesis of (3R)-Hydroxyechinenone, (3R, 3′R)- and (3R, 3′S)-Adonixanthin, (3R)-Adonirubin, Their Optical Antipodes and Related CompoundsThe synthesis of racemic and optically active hydroxyechinenone (12-14), adonixanthin (16-19), adonirubin (22-24), meso-astaxanthin (26) and their corresponding diosphenols 15, 20, 21, 25, 27, 28, and 29) by Wittig reaction is reported, starting from suitable C15-phosphonium salts and C10-aldehydes.
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  • 96
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    Helvetica Chimica Acta 64 (1981), S. 2495-2496 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 97
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981) 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 98
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    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 64 (1981), S. 2497-2507 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Comparison of PE. spectroscopic data for four series of enamines (including azetidine and some aziridine derivatives) for studying the influence of amine-ring size on electronic structure show the pyrrolidino group to exhibit the strongest amine/double bond coupling in sterically unconstrained enamines. However, the azetidino group accommodates best steric congestion due to dialkyl substitution at the β-position of the enamine unit. Quantum-chemical calculations of equilibrium structures and energy profiles for amine rotations in model enamines by the PRDDO SCF method agree satisfactorily with experimental results. Notable exceptions are pyrrolidine derivatives for which PRDDO overestimates the amount of N-pyramidality.
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  • 99
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    Helvetica Chimica Acta 64 (1981), S. 2524-2527 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-Substituted 9-fluorenimines 1 are easily prepared from primary amines or aminoesters and 9-fluorenimine: their conjugate carbanions 2 are formed by the action of alkoxides and are reprotonated to 1 or to the tautomeric 9-alkylidenamino-fluorenes 3 depending upon substituents.
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  • 100
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Anchimerically assisted rearrangement, observed in the fluorination of some α-amino acids with 70 : 30 (w/w) hydrogen fluoride/pyridine (by weight) in the presence of NaNO2, is substantially or fully suppressed by using the less acidic reagent 48 : 52 (w/w) hydrogen fluoride/pyridine.
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