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  • Cis-2,5-diaminobicyclo[2.2.2]octane : a novel C₂-symmetric scaffold for asymmetric catalysis

    Creator:
    Shaw, Subrata
    Abstract:
    This thesis describes the development of a new enantioselective synthetic method employing chiral cis-2,5-diaminobicyclo[2.2.2]octane-based organometallic catalysts. The significance of this new method to organic synthesis is illustrated with preparation of enantioenriched products that are transformed to important pharmaceutical agents. Chapter 1 provides a brief historical overview of asymmetric catalysis, especially...
    Resource Type:
    Dissertation
    Full Text:
    , No. 2. 4. Chen, C. S.; Shieh, W. R.; Lu, P. H.; Harriman, S.; Che, C. Y. Biochimica et Biophysica

  • Tandem intramolecular photocycloaddition-retro-Mannich fragmentation as a route to indole and oxindole

    Creator:
    Li, Yang
    Abstract:
    Irradiation of a tryptamine linked through its side-chain nitrogen to an alkylidene malonate residue results in an intramolecular [2 + 2] cycloaddition to the indole 2,3-double bond. The resultant cyclobutane undergoes spontaneous retro-Mannich fission to produce a spiro[indoline-3,3-pyrrolenine] with relative configuration defined by the orientation of substituents in the transient...
    Resource Type:
    Dissertation
    Full Text:
    ) Oppolzer, W.; Godel, Y. J. Am Chem. Soc. 1978, 100, 2583; (d) Baker, R.; Sims, R. J. Chem. Soc., Perkin

  • Studies toward the total synthesis of (+)-providencin

    Creator:
    Jana, Somnath
    Abstract:
    Studies toward the total synthesis of (+)-providencin (1), a highly oxygenated cembranoid dipterpene with a unique bicyclo[12.2.0]hexadecane skeleton and pronounced biological activity, are described. These studies resulted in the synthesis of advanced intermediates 320 and 332 which contain all of the carbon atoms of 1. In a first generation approach...
    Resource Type:
    Dissertation
    Full Text:
    , Professor Rich G. Carter, Professor Paul R. Blakemore, Professor Kevin P. Gable, Professor Janet Tate and

  • Total synthesis of phorboxazole A

    Creator:
    Lee, Tae Hee
    Abstract:
    The total synthesis of a highly potent cytotoxic marine natural product, phorboxazole A, is described. Both a palladium(II)-mediated and a palladium(II)-catalyzed intramolecular alkoxycarbonylation were used as key steps for the preparation of the two cis-2,6-disubstituted tetrahydropyran rings (C22-C26 and C11-C15) of phorboxazole A. The synthesis used a convergent approach involving...
    Resource Type:
    Dissertation
    Full Text:
    . 2000, 122, 10033. (b) Li, D.-R.; Zhang, D. -H.; Sun, C. -Y.; Zhang, J. -W.; Yang, L.; Chen, J.; Liu

  • Studies towards the total synthesis of (-)-kendomycin

    Creator:
    Smits, Helmars
    Abstract:
    Studies towards the total synthesis of (−)-kendomycin (1), a bacterial metabolite with a unique molecular architecture and pronounced biological activity, are described. These studies resulted in the synthesis of advanced intermediate 208, containing all of the carbon atoms of 1. A Dötz annulation between alkyne 122 and novel chromium carbenoid...
    Resource Type:
    Dissertation
    Full Text:
    OMe O O RO 69 R = H 70 R = MOM 71 R = Ac O O OAc O O O O O OTES TESO OTES O 72 73

  • Total synthesis of (-)-7-epicylindrospermopsin

    Creator:
    Hansen, Joshua D.
    Abstract:
    The first asymmetric synthesis of (-)-7-epicylindrospermopsin via intramolecular nitrone cycloaddition is described. The synthesis utilized a convergent approach to prepare the cycloaddition precursor 176, which was assembled by condensation of hydroxylamine 175 with aldehyde 145. Hydroxylamine 175 was synthesized from ethylene glycol (166) in seven steps. Aldehyde 145 was completed...
    Resource Type:
    Dissertation
    Full Text:
    steps from (R)-methionine. Intramolecular nitrone cycloaddition of 176 afforded the unstable

  • Synthesis of metabolites from the ascomycetes : I. The synthesis and absolute configuration of leptosphaerin : II. Approaches to the synthesis of byssochlamic acid

    Creator:
    Pallenberg, Alexander J.
    Abstract:
    Part I. The total synthesis of (+)-leptosphaerin (2), a metabolite of the marine Ascomycete Leptosphaeria Oraemaris (Linder) was achieved, unambiguously establishing both the relative and absolute stereochemistry of this natural product. This synthesis also resolved the long-standing question of which of the isomeric structures 1 or 2 correctly represents the...
    Resource Type:
    Dissertation
    Full Text:
    mannitol and ethyl pyruvate. In the key step a protected form of R-(+)-glyceraldehyde (3) underwent a

  • Synthesis of a model of the spiroketal portion of avermectin B

    Creator:
    Warrier, Ulhas S.
    Abstract:
    Avermectin Bia is a member of a class of medicinally important natural products known for its potent antiparasitic activity and interesting structural features. In this thesis, synthesis of a model for the spiroketal portion of the avermectins is presented. Oxidation of (S)-2-methylbutanol, followed by a stereoselective chromium mediated reaction with...
    Resource Type:
    Masters Thesis
    Full Text:
    Bla Abstract approved: Redacted for privacy r Dr. James D. White Avermectin Bia is a member of a

  • Studies on the synthesis of the "northern" and "southern" segments of boromycin and aplasmomycin

    Creator:
    Kang, Myung Chol
    Abstract:
    The stereocontrolled synthesis of the southern lactone 17 of boromycin and of the northern segments of both boromycin and aplasmomycin are described. The syntheses begin with enantioselective epoxidation of 3-buten-2-ol (42) to provide the optically active 2(S),3(R) epoxy alcohol 43. The absolute configuration was confirmed by preparing 43 from (-)-2,3-dihydroxybutyric...
    Resource Type:
    Dissertation
    Full Text:
    begin with enantioselective epoxidation of 3-buten-2-ol (42) to provide the optically active 2(S),3(R

  • Approaches to the synthesis of methymycin

    Creator:
    Raghavan, Palaykotai Rajagopalan
    Abstract:
    Several approaches to the synthesis of methymycin were investigated. Segment A (39), containing functionality corresponding to C-9, 10, and 11 of methynolide was made in six steps from propionaldehyde in an overall yield of 37%. Oxidation of 34 with silver nitrate gave 35 which, upon hydroxylation with hydrogen peroxide, gave...
    Resource Type:
    Dissertation
    Full Text:
    . The (+) acid was found to have R,R configuration. This substance was converted to its acetonide