Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Hybridnaturstoffe: Synthese cyclischer Hydroxamsäuren der Estra-1,3,5(10)-trien-Reihe (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 2345-2351 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An approach to a new class of cyclic hydroxamic acids is described leading to a formal combination of a benzoxazine subunit related to some natural aglucones occurring in plants with the steroidal skeleton from two members of the estra-1,3,5(10)-triene series. The annelation procedure for a 4-hydroxy-1,4-oxazine moiety to the aromatic A-ring in estrone (1) and 1-hydroxy-4-methylestra-1,3,5(10)-trien-17-one (7), used as steroidal precursors, proceeds in four or three steps, respectively (Schemes 1 and 2, resp.). First, a 2-nitro group is introduced regioselectively by a novel nitrosation-oxidation procedure or by conventional nitration (→ nitrophenols 2 and 8). Reaction of the phenolic unit of 2 and 8 with methyl bromoacetate or ethyl chlorooxoacetate gives rise to the nitro esters 3, 4, 9, and 10, which are subjected to reductive cyclization either by means of Zn dust in ammonium chloride solution (for the acetates) or of H2/Pt(S)/C (for the sensitive oxalates). Hence, the novel cyclic hydroxamic acids 5, 6, 11, and 12 of the estra-1,3,5(10)-triene series are obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800807
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    A group 4 metallocene template synthesis of β,γ-unsaturated ε-hydroxy carboxylic acids (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2119-2126 
    Details
    ISSN: 0009-2940
    Keywords: Zirconocene complexes ; (Metaloxy)carbene complexes ; Template reaction, organometallic ; Steroid side-chain attachment ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of (butadiene)zirconocene with hexacarbonyltungsten gives the metallacyclic [(π-allyl)zirconoxy]carbene complex 7. This reagent adds to a variety of ketones to yield chiral nine-membered metallacyclic ring systems (8). These systems are thus formed by means of 1,4-selective coupling reactions of 1,3-butadiene with W(CO)6 and an organic carbonyl compound at the zirconocene template. The ketones subjected to react with 7 include benzophenone, methyl vinyl ketone, cyclopentanone, and 3-methoxyestra-1,3,5(10)-trien-17-one (12). The coupling products of 7 with cyclopentanone (8c) and 12 (8d-A) were characterized by X-ray crystal structure analyses. Of the four possible diastereomeric nine-membered metallacyclic coupling products of 7 with 12 a single isomer [8d-A with (13'S,17'R,2,3,4-pS) configuration] was formed with ≥98% selectivity and isolated in 95% yield. Treatment of the complexes 8 in tetrahydrofuran with water and pyridine N-oxide very effectively removed both transition metals with the formation of the corresponding β,γ-unsaturated ε-hydroxy carboxylic acids. The overall reaction sequence has thus converted the steroid ketone 12 very selectively to 5-[3-methoxy-17β-hydroxyestra-1,3,5(10)-trien-17α-yl]-(E)-pent-3-enoic acid (10d)
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260923
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Steroids as Chiral Ligands: Different Molecular and Crystal Structures of Copper(II) Complexes of Mono- and Dideprotonated 16β-Salicylideneimino-17β-hydroxy-3-methoxyestra-1,3,5(10)-triene (1996)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 129 (1996), S. 1497-1501 
    Details
    ISSN: 0009-2940
    Keywords: Steroids ; Chiral amino alcohols ; Copper(II) salicylideneimine complexes ; X-ray analysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The steroidal 16β-salicylideneimino-17β-hydroxy compound 1, synthesized from the corresponding 16β, 17β-amino alcohol, served as a new tridentate chiral ligand for Cu2+-complexation. The X-ray data for 1 and for two dimeric copper complexes 2 and 3 are presented and discussed. Using copper(II) acetate for complexation, dideprotonation of 1 is observed. The neutral complex 2 obtained is characterized by a central planar four-membered copper - oxygen ring. The cycloaliphatic 17β-oxygen anions are bridging atoms; the copper ions are tetracoordinated. Reaction of 1 with copper(II) perchlorate gave only monodeprotonation of the phenolic groups. These oxygen anions are now the bridging atoms; furthermore the two copper ions are bridged by a perchlorate anion. Thus the central four-membered ring is folded (22°), and the copper ions are hexacoordinated (binding of a molecule of water). The crystal lattices of 2 and 3 are also quite different.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19961291216
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Synthesen von 20-Carbaldehyden und 20-Carbonitrilen der Pregnanreihe aus (20S)-20-Hydroxymethylpregna-1,4-dien-3-on (1994)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1994 (1994), S. 1025-1032 
    Details
    ISSN: 0170-2041
    Keywords: Pregnanes ; Steroids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of 20-Carbaldehydes and 20-Carbonitriles of the Pregnane Series Starting with (20S)-20-Hydroxymethylpregna-1,4-dien-3-oneAn efficient six-step approach to 3-protected (20S)-3β-hydroxypregna-1,5-diene-20-carbaldehydes 8 with potential importance in the synthesis of vitamin D analogues was developed starting with (20S)-20-hydroxymethylpregna-1,4-dien-3-one (1). Oxidation of the 22-hydroxy group of 1 by means of periodinane 2 (Dess-Martin reagent) furnished the aldehyde 3 without epimerization. 3 was protected selectively at C-22 as dimethyl acetal 5. Isomerization to 6 and subsequent reduction of the 3-carbonyl group with calcium borohydride furnished the 3β-alcohol 7a with high stereoselectivity. Cleavage of the acetal to 8a occurred in a homogeneous solution of acetic acid in the presence of small amounts of water and trifluoroacetic acid. After protection of the 3-OH group 8b-d were obtained in 54% overall yield. The in situ generated aldehyde N,N-dimethylhydrazones of 3, 8a, and 8b were converted in high yields with excellent chemoselectivity into the nitriles 12, 15a, and 15b with magnesium monoperoxyphthalate hexahydrate. The uniform (20S) stereochemistry of 3 and 8a-d was elucidated by 1H-NMR investigations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199419941012
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...