A highly efficient and general approach to fused ether ring systems has been presented. The approach couples stereoselective C-glycoside forming reactions with subsequent annulations. C-glycosides were formed from glycals through an oxidation and carbon-carbon bond forming sequence. Annulations involving a two step methylenation/enol ether-olefin ring closing metathesis or a single flask, acid mediated cyclization/elimination proved to be efficient tribenzyl- D-glucal (95), [4.4.0] and [4.5.0] bicyclic enol ethers (194, 200, 204) were stereoselectively generated in 2-4 steps in good overall yields (53%, 57%, and 39% respectively). Iteration resulted in the stereoselective formation of tricylic enol ethers (240, 241). In addition, our C-glycoside approach was applied to the synthesis of fused ether containing natural products. A formal synthesis of (±)-hemibrevetoxin B (2) was achieved by intercepting Mori's intermediate ( 278) in 21 steps and 3.8% overall yield. The C-glycoside approach to fused ethers was also demonstrated in the synthesis of halichondrin B's model compounds, bicycle 374 and tricycle 383. Subsequent fragmentation of 383 resulted in bicyclic alcohol 384 which correlates to the C,23-C,38 subunit of halichondrin B (8).
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/280230 |
| Date | January 2001 |
| Creators | Allwein, Shawn Paul |
| Contributors | Rainier, Jon D. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Dissertation-Reproduction (electronic) |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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