✦ LIBER ✦
Diels-Alder Approach to Highly Functionalized Tertiary α-Hydroxy Ketones: A Novel Route to the Hexahydrobenzofuran Portion of the Avermectins and Milbemycins
✍ Scribed by Robert E. Ireland; Daniel M. Obrecht
- Publisher
- John Wiley and Sons
- Year
- 1986
- Tongue
- German
- Weight
- 939 KB
- Volume
- 69
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
A highly regio-and stereoselective Diels-Alder reaction between dienophiles of type I and dienes of type I1 (Scheme I ) gives rise to Diels-Alder adducts of type 111. Upon treatment with BF,. Et,O, these adducts are smoothly converted into the corresponding enones (Scheme 6). Under mild acidic conditions, enone (+)-33 gave bicyclic diketone (+)-34 via an intramolecular Michrrel-type addition. Diketone (*)-34 has the correct relative configuration and a suitable ketone function at C(6) for further conversion into the hexahydrobenzofuran portion of the avermectins and milbemycins.