Studies toward the total synthesis of altromycin natural products Open Access

Koo, Bon Suk (2007)

Permanent URL: https://etd.library.emory.edu/concern/etds/41687j05t?locale=en
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Abstract

Part 1. Synthesis of the Branched C-Glycoside Substructure of Altromycin B.

Tungsten-catalyzed cycloisomerization of alkynyl alcohol provides only the endocyclic enol ether as a key intermediate for the branched C-glycoside substructure of altromycin B. A sequence of Stille cross-coupling reaction and regio- and stereoselective functional group transformations affords each C13-diastereomer of the branched C-arylglycoside.

Part 2. Fischer Carbene Catalysis of the Alkynol Cycloisomerization: Application to the Synthesis of the Altromycin B Disaccharide.

The tungsten-catalyzed cycloisomerization of alkynols can be conducted without using photochemistry, using a stable tungsten Fischer carbene as the precatalyst for this transformation. A variety of alkynyl alcohols undergo cycloisomerization under these conditions to provide endocyclic enol ethers of 5, 6, and 7-membered ring sizes. The utility of this method is further demonstrated in the stereoselective synthesis of the disaccharide substructure of altromycin B.

Table of Contents

  • Part 1. Synthesis of Branched C-Glycoside Substructure of Altromycin B.
    • 1. 1. Introduction and Background
    • 1. 2. Results and discussion
      • 1. 2. 1. Experiments for the formation of C-glycoside linkage (Hallberg's multiple Heck reaction).
      • 1. 2. 2. Experiments for the formation of C-glycoside linkage (Yoshida's multiple Heck reaction).
      • 1. 2. 3. Experiments for the formation of C-glycoside linkage(Stille cross coupling reaction).
      • 1. 2. 4. Synthesis of branced C-glycoside substructure of altromycin B.
    • 1. 3. Conclusions
    • 1. 4. Experimental Section
    • 1. 5. References
  • Part 2. Fischer Carbene Catalysis of the Alkynol Cycloisomerization: Application to the Synthesis of the Altromycin B Disaccharide.
    • 2. 1. Introduction and Background
    • 2. 2. Results and discussion
      • 2. 2. 1. Design and hypothesis of Fischer carbene catalysis.
      • 2. 2. 2. Optimization of reaction conditions.
      • 2. 2. 3. Comparison of non-photochemical and photochemical procedures.
      • 2. 2. 4. Proposed mechanism for the Fischer carbene catalysis.
      • 2. 2. 5. Synthesis of the east disaccharide substructure of altromycin B.
    • 2. 3. Conclusions
    • 2. 4. Experimental Section
    • 2. 5. References

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