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  • 1
    ISSN: 0947-3440
    Keywords: cis-[1.1.1]-Tris-σ-homobenzenes ; [σ2s+σ2s+σ2s] Cycloreversions ; Substituent effects ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By triple epoxide → cyclopropane transformation starting from cis-benzene trioxide the 3α,6α,9α-tris(TIPS-ethynyl) (1b), -tris(alkoxycarbonyl) (1d, e), -tricyano (1f), and -tris(ammoniomethyl) (1j) derivatives of the still elusive parent cis-[1.1.1]-tris-σ-homobenzene (1a) have been synthesized. Out of a number of carbon nucleophiles tested, a weakly basic mixed cyanocuprate of Li-TIPS-propyne proved the reagent of choice: Eliminations were largely avoided, the scylloDescriptors scyllo, chiro, allo, cis are used as in inositol nomenclature; TIPS- = iPr3Si-.-2,4,6-tris(TIPS-propargyl)cyclohexane-1,3,5-triol (13a), obtained in a stereoselective one-pot threefold epoxide opening (up to 69%), allowed the pertinent functional group manipulations. The selectivity of the base-induced triple cyclopropane ring closure in the flexible cyclohexane precursors strongly depends on the activating groups and is promoted by fixation of the “all-axial” conformation as an adamantoid orthophosphate. The ΔG≠ values determined for the generally neat 3σ → 3π isomerizations [28.5 (1e), 29.0 (1f), 22.6 (1j) kcal mol-1] are in line with concerted reaction courses ([σ2s+σ2s+σ2s]). For the trinitrile 1f an X-ray structure analysis confirmed a nearly planar cyclohexane ring and a relatively large cyclohexane/cyclopropane interplanary angle (113°).
    Additional Material: 6 Ill.
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  • 2
    ISSN: 0947-3440
    Keywords: Antibiotics ; Sannamycin-type ; Mirror-images ; Syntheses ; Activity, biological ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sets of variously protected purpurosamine/2-epi-purpurosamine-type glycosyl donors (O-acetates) and sannamine-type glycosyl acceptors were coupled as racemates and pure enantiomers, according to a modified Koenigs-Knorr procedure with TMSOTf as promotor. The α anomers isolated from the respective mixtures of glycosides (yields varying between 51% and 91%, α:β anomeric ratios between 1.5:1 and 13:1, α:α′ diastereomeric ratios between 1:1 and 1:1.5) were transformed through standard protection/deprotection and glycidation measures into 6′-des(N-methyl)sannamycins A (1, 1′, 2, 2′) and B (37, 37′), 2′-epi-6′-des(N-methyl)sannamycins (3, 3′), the enantiomeric sannamycins A and B (ent-4)/ (ent-40), the diastereomers (ent-4′)/(ent-40′), and the enantiomeric 2′-epi-sannamycin A (ent-5)/(ent-β-5). For one of the fluorinated glycosides (α-26′), featuring a somewhat unusual aglycon conformation, an X-ray structural analysis was performed. In explorative biological tests, the naturally configurated glycosides 1 and 3 showed limited, 2 a rather broad activity against a number of pathogenic microorganisms. Yet, none of the glycosides with non-natural configuration was found to be active.
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  • 3
    ISSN: 0947-3440
    Keywords: (Seco)dodecahedradienes ; PE spectroscopy ; π,π Interaction, nonconjugated, through-space, through-bond ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nature and extent of nonconjugated π,π interactions in (bis)-secododecahedradienes and (pentagonal, non-pentagonal) dodecahedradienes with transannular π,π distances ranging from ca. 2.8 to ca. 3.5 Å - representing well defined points on the D2h [π2 + π2] reaction coordinate - were studied by PE spectroscopy. The π,π splitting of 0.68 eV measured at the largest π,π distance of ca. 3.5 Å (1,16-dodecahedradiene 3a) was attributed to ca. 50% each of through-space and through-bond conjugation (analysis of precanonical MOs).
    Additional Material: 5 Ill.
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  • 4
    ISSN: 0947-3440
    Keywords: 1,4-cis-Diaminotetra(di)deoxyheptitols ; Tropa-type heterocycles ; Total syntheses ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthetic potential of the dianhydrocycloheptenepentols 3 and dianhydrocycloheptaneheptols 4 - ultimately available from tropilidene - as intermediates en route to 1,4-cis-diaminotetra(di)deoxyheptitols is studied. With standard bivalent N nucleophiles (methyl-, benzylamine, hydrazines) the regioselective installation of two (e.g. 9, 34) amino functions has to compete with the generation of variously functionalized tropa-type 8-azabicyclo[3.2.1]octanes (e.g. 29, 30, 35, 45, 47). With azide (N3-) as monovalent nucleophile in unsaturated diepoxides 3 twofold, nearly regiospecific substitution (7) - in competition with [3,3]-sigmatropic migration (SN2′ substitution) -, in saturated diepoxides 4 regioselective monosubstitution (39) can be achieved.
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  • 5
    ISSN: 0947-6539
    Keywords: cage effects ; dodecahedranes ; organic synthesis ; pagodanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two variants of the “SN2 route” from pagodanes (A, B) to functionalized dodecahedranes (D, F) and particularly dodecahedradienes (E) offer considerable improvements in the number of operations (from nine to five to three) and yields (e.g., for diester F from 55-65 to 70-75 to 85-91%). Key steps are the regio- and stereospecific introduction of four to six bromine substituents into dimethyl pagodane-4-syn,9-syn-dicarboxylate (1 b) and a highly complex (thirteen bond-breaking/bond-forming events in four participating structures). yet very convenient (one-pot operation) and extremely efficient (nearly quantitative) transformation of secopagodane to bissecododecahedradiene with complete stereocontrol in transannular CH2 functionalizations. The prohibitively low kinetic acidity of “caged” hydrogens has so far only been overcome with the recently reported P2F reagent (Schwesinger). Further improvement of the overall economy of the pagodane → dodecahedrane scheme has been achieved by efficiently channeling a byproduct of the pagodane synthesis (ca. 10%) back into the SN2 track.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 101 (1968), S. 4066-4082 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Darstellung der Tricyclo[3.2.1.02.4]octen-Derivate 20a, 21a, 22a und 23a, wird beschrieben. Während 21a und 23a thermisch bis mindestens 270° stabil sind, erfahren 20a und 22a schon knapp oberhalb 200° eine tiefgreifende Skelettumwandlung: als Pyrolyseprodukte werden 25a, 26a und 27a bzw. 30a und 31a identifiziert. Ein über das 6-Vinyl-bicyclo[3.1.0]-hexen-Derivat 40a führender Mechanismus wird diskutiert.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 101 (1968), S. 4083-4098 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Durch direkte Lichtanregung gelingt die Valenzisomerisierung der Homovinyl-cyclopropan-systeme 7, 15 und 16 zu den Bis-homo-cyclopentadien-Derivaten 9, 17 und 20. Der Anteil dieser [2°+2σ]-Cycloadditionen am photochemischen Geschehen wird wesentlich durch stereoelektronische Faktoren und durch Milieueinflüsse bestimmt.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 103 (1970), S. 2288-2301 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Photochemical Transformations, 33Upon direct photoexcitation the three 7-azabenzonorbornadienes 12a, b, c are isomerized to the 3-benzazepines 22a, b, c. At temperatures above -40° the azaquadricyclanes 19a, b, c, postulated as intermediates, cannot be found. The sensitized reaction of 12a yields the 6-aminobenzofulvenes 23a and 24a preferentially.
    Notes: Durch direkte Lichtanregung werden die drei 7-Aza-benzonorbornadiene 12a, b, c in die 3-Benzazepine 22a, b, c isomerisiert. Oberhalb -40° lassen sich die als Zwischenprodukte postulierten Azaquadricyclane 19a, b, c nicht nachweisen. Bei der sensibilisierten Anregung von 12a werden die 6-Amino-2.3-benzo-fulvene 23a, 24a bevorzugt gebildet.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 104 (1971), S. 2489-2516 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Phenyl Substituted Quadricyclane Esters - Synthesis, Thermolysis, CycloadditionsThe 1.4- and 1.5-diphenyl substituted norbornadiene esters 6a, b, 9a, b and some dihydro derivatives (18, 19) are synthesized. The corresponding quadricyclanes 7a, b, 10a, b are obtained upon direct irradiation. Depending on the position of the phenyl substituents the thermal stability of the quadricyclanes varies considerably; the course of their pyrolysis reaction and approximate half-lives are determined. The sensitized (acetone) photolysis of 6a, b leads to the tricyclo[3.2.0.02.7]heptene derivatives 31, and 25, 27, resp. Judged by preliminary results the di-π-methane transformation is also the favorite pathway in the case of 9a, b. Cycloaddition reactions between 7a, 10b, and dimethyl acetylenedicarboxylate or methyl propiolate yield the 1:1 adducts 33a, b and 38.
    Notes: Die 1.4- und 1.5-Diphenyl-norbornadienester 6a, b und 9a, b sowie einige Dihydroderivate (18, 19) werden synthetisiert. Durch direkte Lichtanregung erhält man die entsprechenden Quadricyclane 7a, b und 10a, b, deren thermische Beständigkeit je nach der Stellung der Phenylreste beträchtlich variiert (Pyrolyserverlauf und angenäherte Halbwertszeiten werden bestimmt). Die durch Aceton sensibilisierte Photolyse von 6a, b liefert die Tricyclo[3.2.0.02.7]-hepten-Derivate 31, bzw. 25, 27. Nach vorläufigen Befunden ist die Di-π-Methan-Umlagerung auch im Falle von 9a, b bevorzugt. Bei der Umsetzung von 7a, 10b mit Acetylendicarbonsäure-dimethylester oder Propiolsäure-methylester werden die 1:1-Addukte 33a, b bzw. 38 erhalten.
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  • 10
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Proton Resonance Spectroscopy of Unsaturated Ringsystems, XVIII.XVII. Mitteil.: D. Cremer und H. Günther, Liebigs Ann. Chem. 763, 87 (1972) A Benzeneimine-1 H-Azepine EquilibriumThe temperature dependence of the 1H n.m.r. spectrum of 4,5-bis(methoxycarbonyl)-3,6-diphenyl-1-p-tosyl-1H-azepine (11) is described. The results are interpreted on the basis of a benzeneimine-1H-azepine valence tautomerism (equilibrium distribution at room temperature ca. 3 : 97).
    Notes: Es wird über die Temperaturabhängigkeit des 1H-NMR-Spektrums von 4,5-Bis(methoxycarbonyl)-3,6-diphenyl-1 -p-tosyl-1H-azepin (11) berichtet. Die Befunde werden im Sinne einer Benzolimin-1H-Azepin-Valenztautomerie (Gleichgewichts-Verteilung bei Raumtemperatur ca. 3 : 97) interpretiert.
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