Variable Stereocontrol in Cycloadditions of 1,7,9-Decatrien-3-ones by Different Lewis Acidic Promoters – Application to a Short Synthesis of α-Eudesmol
✍ Scribed by Barbara Frey; Jürgen Schnaubelt; Hans-Ulrich Reißig
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 319 KB
- Volume
- 1999
- Category
- Article
- ISSN
- 1434-193X
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✦ Synopsis
3-ones / α-Eudesmol / Lewis acids / Chelates Trienones 1-3 were subjected to Lewis acid-promoted predominantly the exo product trans-b via seven-membered ring chelate intermediates. The chelate-controlled intramolecular Diels-Alder reactions. It was shown that with monocoordinating Lewis acids the endo selectivity of the intramolecular Diels-Alder reaction was then utilised as the key step in a stereocontrolled synthesis of the sesquiterpene cycloaddition was generally high. The preference for either of the two possible endo products cis-a and cis-b, however, α-eudesmol. This reaction mode, performed on a model trienone, also paved the way for the synthesis of the was shown to be highly dependent on the nature of the Lewis acid, and on the substitution pattern of the trienone pharmaceutically important natural product dihydromevinolin. substrates. Lewis acids with two coordination sites furnished ber of earlier examples on intramolecular DielsϪAlder reacids. The monocoordinating Lewis acids, usually with one D-01062 Dresden, Germany coordination site, influence the reaction only by binding to