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  • 1
    Electronic Resource
    Electronic Resource
    Triaziridines. Part VPart IV, see [1].. A semiempirical MNDO study of nitrogen inversion and amide rotation in Formyltriaziridines (1986)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 1461-1468 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Since we found certain structural features of triaziridine (1) obtained by MNDO calculations to be in qualitative agreement with those derived earlier from ab initio calculations, we used the MNDO method to derive properties of formyltriaziridine (2) and 1-formyl-2,3-diisopropyltriaziridine (3) as models for the preparatively known 2,3-dialkyl-triaziridine-1-carboxylates 4 and 5. The main results are: (a) The triaziridine N-atoms with H, alkyl, or formyl as substituents (see 2 and 3) are pyramidal. N(1) carrying the formyl group is flatter than N(2) and N(3) with H or alkyl substitent. Bond lengths and angles at N(2) and N(3) are almost identical with those calculated for the N-atoms of 1. (b) The MNDO inversion barriers at the H-substituted N(2) and N(3) of 2 are higher than those at the formyl-substituted N(1), but similar to the ab initio barriers at the N-atoms of 1. (c) The MNDO inversion barriers at N(1) of 2 and 3 are 53 to 92 kJ/mol, whereas the rotation barriers around the N(1)-C(4) bond are 7 to 23 kJ/mol; thus, the previously observed dynamic NMR phenomena in trans-2,3-diisopropyltriaziridine-carboxylates (5) can now be assigned to the slowing down of N(1) inversion rather than N(1)-C(4) rotation.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19860690618
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  • 2
    Electronic Resource
    Electronic Resource
    Short Syntheses of (±)-Grandisol and (±) Lineatin via, a common Intermediate (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 1302-1306 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A 6-step synthesis of (±)-grandisol (1) is presented, which involves dichloroketene addition to 3-methyl-3-butenyl acetate (4), reductive dechlorination of the adduct 6 to the ketone 7 and saponification to 8, aldolization of 7 or 8 with acetone and cyclization to the bicyclic ketone 9, Wolff-kishner, reduction to 14, and finally ring opening to 1. Since 9 is a known intermediate of the synthesis of (±)-lineatin (2), the latter can now be obtained in 6 steps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19870700510
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  • 3
    Electronic Resource
    Electronic Resource
    Ringerweiterung bei der Reaktion eines 1,3-Cyclohexandions mit Diphenylcyclopropenon (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 2140-2147 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ring Expansion during the Reaction of a 1,3-Cyclohexanedione with DiphenylcyclopropenoneThe reaction of 5,5-dimethyl-1,3-cyclohexanedione (1) in form of its Na-salt with diphenylcyclopropenone (2) in DMF yielded the bicyclic triketone 3 (58 %), the structure of which was deduced as an enolizeable bicyclo[5.2.0]nonane-β-diketone from spectral data and from the following reactions: hydrolysis or methanolysis of 3 cleaved the β-dicarbonyl moiety, thereby opening the 4-membered ring to yield the keto acid 9 or its methyl ester 10. Methylation of 3 afforded the two enol ethers 4 and 5. The ether 5 readily underwent a thermal electrocyclic ring opening to the monocyclic enol ether 8, whereas the ether 4 was thermally stable. The same electrocylic ring opening (in boiling benzene) converted 3 (probably via 3b) to the monocyclic triketone 7, which was also the hydrolysis product of the ring-opened enol ether 8. By heating 3 in DMF/H2O, a partial (56 %) conversion to the lactone 6 took place. The tricyclic intermediate 11 was found useful to rationalize the ring expansion during the formation of 3 from 1 and 2 as well as the corresponding ring contraction during the conversion of 3 into 6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680808
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  • 4
    Electronic Resource
    Electronic Resource
    Cyclobut-2-enones from Alkynes via Dichlorocyclobut-2-enonesIn part taken from the Ph.D. thesis of A.A.A., University of Zürich, 1986. (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 321-328 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The [2 + 2]-cycloaddition of dichloroketene (prepared in situ from CCl3COCl and Zn(Cu)) with three alkynes 1a-c to form 2,3-dimethyl-(2a), 2,3-diethyl-(2b) and 3-butyl-4,4-dichlorocyclobut-2-enone (2c) proceeds rapidly in the absence of POCl3. The primary products 2a-c rearrange in situ to the 2,4-dichlorocyclobut-2-enones 3a-c under the influence of ZnCL2 produced during the reaction. ZnCl2 converts both 2a and 3a into a 4:6 equilibrium mixture of the two; this isomerization does not occur with LiCl. The Cl-atoms of both 2a, b and 3a, band of 2c may reductively be removed with Zn(Cu) in AcOH/pyridine to afford the alkylcyclobutenones 4a-c. Without pyridine, this reduction gives ca. 1:1 mixtures of the double-bond isomers 4 and 5 in low yields. The cyclobutenones 2c and 4c may be deuterated by CD3COOD in the presence of pyridine. D-Atom is introduced into 2c at C(4) and at C(γ), and into 4c at C(2) and C(4). A mechanism for this deuteration is considered, which does not involve a cyclobutadienolate 7, but rather a cyclobutenolate of type 8. The reductions of 2 and 3 to 4 might also pass through the same type of intermediate 8.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19870700208
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  • 5
    Electronic Resource
    Electronic Resource
    Umwandlung eines Betacyans in ein Betaxanthin Synthese von Indicaxanthin aus BetaninVon A.S.D. im Rahmen von 2 Vorträgen an der Universität Göttingen und am «Symposium on Recent Advances of Plant Phenolics» in New Delhi am 24. 9. und 5. 10. 64 bekannt gegeben. (1965)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 48 (1965), S. 361-366 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When betanin (III) was treated with S-proline (IV), a base exchange took place which produced indicaxanthin (I). In this way this yellow pigment of the cactus fruit was partially synthesized by a method which should be generally applicable for the mutual interconversion of betacyanins and betaxanthins. For it was also possible to transform indicaxanthin into betanidin (II) by a base exchange with 5,6-dihydroxy-2,3-dihydroindole-2S-carboxylic acid (V).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19650480214
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  • 6
    Electronic Resource
    Electronic Resource
    Derivate der Betalaminsäure (1965)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 48 (1965), S. 1922-1927 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Betalamic acid, the structural unit which is characteristic for the watersoluble centrospermae pigments, the betacyanins and the betaxanthins, has been prepared as the semicarbazone of the dimethyl ester by a “base exchange reaction” from betanidin trimethyl ester and semicarbazide. The UV.- and NMR.-spectra support the proposed structure. The semicarbazone has been reconverted to betanidin trimethyl ester by means of cyclodopa methyl ester.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19650480810
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  • 7
    Electronic Resource
    Electronic Resource
    Präbetanin, ein Schwefelsäure-halbester des Betanins. Ein Beitrag zur Kenntnis der Betacyane (1967)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 50 (1967), S. 545-561 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Prebetanin, a minor companion of betanin in the red beet, was isolated and found to be the 6′-sulfuric acid half-ester of betanin. The arguments are based on elemental analyses, partial hydrolysis and methanolysis, and on comparison of the NMR-spectra of prebetanin and betanin, and of their derivatives.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19670500220
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  • 8
    Electronic Resource
    Electronic Resource
    Umsetzungen des Cyclohex-3-en-carbaldehyd-p-toluolsulfonylhydrazonsEin Teil dieser Resultate wurde am 1964-Symposium «Modern Aspects of Stereochemistry» in Sheffield, England, vorgetragen [1]. (1968)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 51 (1968), S. 1001-1010 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The vacuum thermolysis (80-90°) of the sodium salt of cyclohex-3-ene-carbaldehyde p-toluenesulfonylhydrazone (1) in silicone oil gave diazomethyl-cyclohex-3-ene (2). Pyrolytic and photolytic decomposition of this diazo compound 2 lead to methylenecyclohex-3-ene (5) and bicyclo [4.1.0]hept-2-ene (6) (about 3:1), while the CuCl catalyzed cleavage yielded only 5. The postulated carbene mechanism should also apply under the direct aprotic decomposition conditions of the sodium salt of 1 in diglyme, where methylenecyclohex-3-ene and bicyclo[4.1.0]hept-2-ene (about 3:1) were formed besides small amounts of 1-methylcyclohexa-1, 3-diene (9) and bicyclo [4.1.0]hept-3-ene (8). Under protic conditions (in ethylene-glycol) methylenecyclohex-3-ene, 1-methylcyclohexa-1, 3-diene and 1-methylcyclohexa-1, 4-diene (14) were produced in a ratio of 1:1:1.The direct mild thermolysis of cyclohex-3-ene-carbaldehyde p-toluenesulfonylhydrazone (1) in benzene solution afforded N-(p-toluenesulfinyl)-O-(p-toluenesulfinyl)-cyclohex-3-en-yl-α-methanolamine (15) and di-(cyclohex-3-en-yl-methyl)-ammonium p-toluenesulfonate (16), the structures of which were supported by their nmr. spectra and by alkaline cleavage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19680510502
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  • 9
    Electronic Resource
    Electronic Resource
    Biogenese der Betalaine Biotransformation von Dopa und Tyrosin in den Betalaminsäureteil des Betanins. Vorläufige MitteilungEine ausführliche Mitteilung ist in Vorbereitung. (1968)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 51 (1968), S. 1470-1474 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: During studies on the biogenesis of betalains (I) in cactus fruits (Opuntia sp.). DL-dopa-1-[14C] and -2-[14C] were incorporated into betanin (III) which was obtained radiopure after crystallization. The specific activity remained constant after conversion to betanidin (IV) and to a neobetanidin derivative (IX). Reaction of radiobetanin with proline afforded indicaxanthin (V) carrying more than 90% of the radioactivity. Dopa (VI) is thus an efficient precursor for betalamic acid (VIII) but not for cyclodopa (VII). Decarboxylation of radiobetanidin and radioindicaxanthin showed that the carboxyl group of dopa remained a carboxyl group in the biotransformation to betalamic acid. It is concluded that the aromatic ring of dopa is cleaved and that re-cyclization involving the nitrogen generates the dihydropyridine moiety. Under the same conditions mevalonic acid, aspartic acid and phenylalanine showed low incorporations. Studies with beet seedlings and DL-dopa-1-[14C], -2-[14C] and DL-tyrosine-1-[14C] afforded similar results but with low incorporations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19680510634
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  • 10
    Electronic Resource
    Electronic Resource
    Preparation of a 2-Methylcyclodopa Derivative (1970)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 53 (1970), S. 1937-1939 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Herstellung von O,O-Diacetyl-S-2-methylcyclodopa-methylester (7) durch Oxydation von S-2-Methyldopa-methylester (4) und anschliessende Reduktion und Acetylierung ist beschrieben. Im Gegensatz zu Cyclodopa (2) wird 2-Methylcyclodopa-methylester (6) am Stickstoff durch Acetanhydrid und Pyridin nicht acetyliert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19700530745
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