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  • 1
    Electronic Resource
    Electronic Resource
    A new synthesis of (±)-phoracantholide, (±)-dihydrorecifeiolide, and (±)-muscone via α-nitro ketones (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 1381-1383 
    Details
    ISSN: 0947-3440
    Keywords: (±)-Phoracantholide ; (±)-Recifeiolide, Dihydro ; (±)-Muscone ; α-Nitro ketones ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cα′ alkylation of α-nitro cycloalkanones 1a-c with methyl iodide at -35 to -70°C in THF/heptane/DMPU/TMDA in the presence of LDA as a base furnished the methylated α-nitro ketones 2a-c. Denitration of 2a, b with Bu3SnH/AIBN in dry benzene afforded the α′-methylated ketones 3a, b, which were converted to (±)-phoracantholide (4a) and (±)-dihydrorecifeiolide (4b), respectively, by the Baeyer-Villiger oxidation. Reduction of 2c with NaBH4 and dehydration of the obtained nitro alkanol 5 with Al2O3/DMAP furnished the corresponding nitro alkene 6. Nef conversion of 6 with sodium hypophosphite and Raney nickel afforded (±)-muscone (7) in good yields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1995199507185
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  • 2
    Electronic Resource
    Electronic Resource
    Evaluation of chiroptical properties of molecules by asymmetric photochemistry (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 257-262 
    Details
    ISSN: 0899-0042
    Keywords: chiral photochemistry ; excitation transfer ; optical activation ; circular dichroism ; dissymmetry factor ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The physics involved in photochemistry with circularly polarized light, the warnings on its inherent limitations, as well as some examples of application on organic molecules are briefly reviewed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030408
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  • 3
    Electronic Resource
    Electronic Resource
    Photoinduced Double Addition of Acetylene to 3-Oxocyclopent-1-ene-1-carbonitrile or 3-oxocyclopent-1-enyl acetate leading to 2,3-dihydro-1H-inden-1-one and other rearranged products (1988)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 71 (1988), S. 1608-1615 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: UV Irradiation of 3-oxocyclopent-1-enyl acetate (17) and acetylene in MeCN at 0° gives, besides the product of normal enone-alkyne [2 + 2] cycloaddition (cis-4-oxobicyclo[3.2.0] hept-6-en-1-yl acetate, 18) and its product of oxa-di-π-methane rearrangement (5-oxotricyclo[4.1.0.02,7]hept-2-yl acetate, 19), unexpected products of further addition of a molar equivalent of acetylene. These are indanone ( = 2,3-dihydro-1H-inden-1-one, 16), in 21% yield, cis-1-cisoid-1,2-cis-2- (20) and cis-1-transoid-1,2-cis-2-7-oxotricyclo[4.3.0.02,5]non-3-en-1-yl acetate (21), 4-oxo-7-‘exo’-vinyltricyclo[3.2.0.02,6]hept-2-yl acetate (22), cis-4-oxo-6-‘endo’- (23) and cis-4-oxo-6-‘exo’-vinylbicyclo[3.2.0]hept-1-yl acetate (24), and cis-4-oxo-7-‘exo’-vinylbicyclo[3.2.0]hept-1-yl acetate (25). At least in part, indanone must be formed via intermediates 20 and 21. In fact, on heating a 9:1 mixture 20/21, indanone is obtained quantitatively. With 3-oxocyclopent-1-ene-1-carbonitrile (15) in place of 17, indanone is formed in lower (8%) yield besides much tars.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19880710704
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  • 4
    Electronic Resource
    Electronic Resource
    The Molecular and Crystal Structure of the Glycopeptide A-40926 Aglycone (1996)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 79 (1996), S. 1916-1924 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of a glycopeptide antibiotic A-40926 aglycone was investigated by X-ray analysis at -120°. A-40926 crystallises in the orthorhombic space group P212121 with two monomers in the asymmetric unit, a = 21.774(4), b = 28.603(7), c = 29.757(4) Å. ‘Conventional’ direct methods approach failed to solve the structure, but a novel iterative real/reciprocal space procedure was successful. Refinement against 11248 F2 data led to R1 = 13.3% for 6770 F 〉 4σ (F). The two monomers of A-40926 have similar conformations and are bound by antiparallel H-bonds to form a ‘chain’ structure of connecting dimers. The antibiotic molecule possesses a ‘binding pocket’ for the C-terminal carboxy group of the cell-wall protein, which is consisten with suggestions based on NMR data and the recently reported crystal structure of ureido-balhimycin. In A-40926 the monomers are polymerically linked by H-bonds, quite unlike the tight dimer formation observed in ureido-balhimycin.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19960790714
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis of the Alleged Natural Monoterpenoid α-SantolinenonePresented by F.P. as part of a lecture at the University of Innsbruck on March 15th, 1984. (1984)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 67 (1984), S. 1248-1253 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Authentic α-santolinenone ( = (+)-(4R)-1(7)-p-menthen-2-one; (+)-1) is made available for the the first time in 30% overall yield from (+)-(4R)-p-menthene ((+)-2) via the diastereoisomeric allylic alcohols (+)-4a/(+)-4b, which are oxidized to (+)-1 with Ag2CO3/Celite. Yields are good, except for the last stage; indeed, only alcohol (+)-4a, with equatorial OH-group, undergoes oxidation, and (+)-1 is partly substracted via a hetero Diels-Alder dimerization giving a mixture of the diastereoisomeric dihydropyrans (+)-5a/(+)-5b. When Cr(VI) reagents ae used, (+)-4a/(+)-4b mainly give phellandral (6) and carvotanacetone (7), NnO2 reacts too sluggishly with (+)-4a/(+)-4b. A camphor pyrolyzate, previously thought to be 1 must be a different compound, probably 7.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19840670511
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  • 6
    Electronic Resource
    Electronic Resource
    On the Absolute Configuration of Penlanfuran and Related Sesquiterpenoids of the Sponge Dysidea fragilis from the North-Brittany Sea (1990)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 73 (1990), S. 652-658 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1,4-addition of vinylmagnesium bromide/CuBr-SMe2 to (+)-(4s)-cryptone ((+)-6) in THF in the presence of Me3SiCI gives the silylenol ether 7 which partly undergoes hydrolysis to ketone 8 on aqueous workup; residual 7 is hydrolyzed with pyridinium p-toluenesulfonate (PyTsOH) to give 8 which is protected in situ with ethylene glycol and then ozonolized to give aldehyde (—)-10. The latter, on addition of 3-lithiofuran followed by dehydration and deprotection with Py TsOH, gives the unnatural (4S)-enantiomer (+)-2 of noroxopenlanfuran. All processes, except 11 → (+)-2, are of good yield. On the basis of previous chemical transformations, this also establishes the (4R)-configuration for penlanfuran ((-)-1) and other sesquiterpenoids of the sponge Dysidea fragilis from the North-Brittany sea. Non viable routes to (±)-noroxoperlanfuran ((±)-2) are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19900730314
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