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  • Aromaticity  (1)
  • Associated systemic disease  (1)
  • 1995-1999  (2)
  • 1980-1984
  • 1955-1959
  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 1434-1948
    Keywords: Phosphorus heterocycles ; Aromaticity ; Phosphenium cations ; Ab initio calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aromatic stabilization of cyclic phosphenium cations (general type C2N2P+) was studied by experimental methods (synthesis, multinuclear NMR, single crystal X-ray crystallography) and quantum chemical calculations (ab initio methods). The structures of the 1,3,2-diazaphosphole derivatives [(tBuN-CH=CH-NtBu)P+]Cl- (1), (tBuN-CH2-CH2-NtBu)P-Cl (2), [(tBuN-CH=CH-NtBu)P]+PF6- (3) and [(tBuN-CH2-CH2-NtBu)]P+PF6- (4) were examined by single crystal X-ray diffraction. The chloro phosphane [(tBuN-CH=CH-NtBu)P]+Cl- (1) has an ionic P-Cl bond and contains an aromatically stabilized phosphenium cation [shortest distance P···Cl = 275.9(2) pm], while the CC-saturated compound (tBuN-CH2-CH2-NtBu)P-Cl (2) is covalent. The two chloro-phosphanes 1 and 2 differ sharply in their volatility and solubility in organic solvents. Compound 2 is soluble in hydrocarbons and sublimes readily at 90 °C/0.1 Torr but 1 is insoluble in hexanes and not volatile below 180 °C/0.1 Torr. The degree of aromatic stabilization in the phosphenium cation 1 was investigated by ab initio methods. For the model cations [RN-CH2-CH2-NR]P+ and [(RN-CH=CH-NR)P]+, thermochemical stabilization energies of 25.8 kcal · mol-1 (R = H) and 28.1 kcal · mol-1 (R = Me) were obtained from isodesmic hydrogenation reactions at the RHF/MP2/6-31G*//RHF/6-31G* level.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1433-0423
    Keywords: Schlüsselwörter Skleritis ; Episkleritis ; Immunsuppression ; Systemerkrankung ; Key words Scleritis ; Episcleritis ; Immunosuppressant ; Associated systemic disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Numerous systemic diseases can cause scleritis or episcleritis. Frequently, symptoms and complications compromising vision can only be managed with systemic immunosuppressants. There are no clear guidelines on the indications for systemic immunosuppressants in patients with episcleritis and scleritis. Patients and methods. The aim of the present retrospective study was to investigate how many patients with episcleritis or scleritis have an associated systemic disease and at what stage it is diagnosed. Secondly, the proportion of patients who present with episcleritis or scleritis in the first instance and then change into the other category during the course of the disease was analyzed. Finally, we checked whether the presence of an associated systemic disease indicates the necessity to treat the patient with nonsteroidal systemic immunosuppressive drugs. Results. Sixty-eight patients with inflammatory scleral diseases were treated at the University Eye Clinic between 1991 and 1995. In 13 patients an associated systemic disease was diagnosed before the appearance of ocular symptoms, and in 8 patients such an illness was diagnosed at a later stage. In 2 cases (3%) the ocular disease category changed during the course of the disease. Neither in the episcleritis nor in the scleritis population was a statistically significant correlation established between the diagnosis of an associated systemic disease and the necessity to treat the patient with nonsteroidal systemic immunosuppressive drugs. Conclusion. The small number of patients who changed the ocular disease category may indicate that episcleritis and scleritis are two independent entities, which might even be caused by different mechanisms. The indications for the management of episcleritis and scleritis with immunosuppressive drugs should not only depend on the diagnosis of an associated systemic disease, but also and mainly on the severity of the ocular manifestation.
    Notes: Skleritis und Episkleritis können im Rahmen zahlreicher Systemerkrankungen auftreten. In bestimmten Fällen können subjektive Symptome und visusbedrohende Komplikationen langfristig nur durch eine systemische Immunsuppression angegangen werden. Therapeutische Leitlinien zur Immunsuppression bei Episkleritis- und Skleritispatienten fehlen bis heute. Patienten und Methode: In einer retrospektiven Studie wird analysiert, welche systemischen Erkrankungen unserer Patientenpopulation zugrundeliegen und zu welchem Zeitpunkt sie manifest wurden. Es soll überprüft werden, ob eine Skleritis und eine Episkleritis nacheinander am gleichen Auge aufgetreten sind. Weiterhin wird untersucht, ob die Diagnose einer systemischen Erkrankung einen Hinweis auf die Notwendigkeit einer längerfristigen systemischen nichtsteroidalen Immunsuppression gibt. Ergebnisse: Zwischen 1991 und 1995 wurden in der Universitäts-Augenklinik Tübingen 68 Patienten mit entzündlichen Skleraerkrankungen behandelt. Bei 13 Patienten war eine systemische Grunderkrankung vor Beginn der Augenbeschwerden bekannt, bei 8 Patienten wurde sie im weiteren Verlauf diagnostiziert. Weder bei den Episkleritis- noch bei den Skleritispatienten bestand ein statistisch signifikanter Zusammenhang zwischen der Diagnose einer assoziierten Systemerkrankung und der Notwendigkeit einer Therapie mit nichtsteroidalen Immunsuppressiva. Bei nur 2 Patienten (3%) wechselte ein Krankheitsbild in das andere über. Schlußfolgerung: Die geringe Zahl der Übergänge zwischen Episkleritis und Skleritis spricht dafür, daß es sich bei den beiden Krankheitsbildern um 2 eigenständige Entitäten handelt, die möglicherweise durch verschiedene Mechanismen hervorgerufen werden. Die Therapie mit Immunsuppressiva sollte nach unseren Ergebnissen nicht allein von einer Systemerkrankung, sondern vom okularen Befund abhängig gemacht werden.
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