ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The bicyclic keto lactone 26 was synthesized for the purpose of developing a viable route to marine diterpenes of the crenulatan type. Following the efficient conversion of (S)-citronellol (5) to the allylated alcohol 9a (Scheme 2), the αβ-unsaturated lactone 12 was efficiently accessed in preparation for stereocontrolled conjugate addition. The hydroxymethyl equivalent most suited to this task was (i-PrO)Me2SiCH2MgCl, which gave 13 predominantly in the presence of CuI and Me3SiCl. Once the OH group was deprotected (→ 14), it proved an easy matter to implement acid-catalyzed isomerization to lactone 15, oxidation of which gave the pivotal aldehyde 16. Condensation of 16 with PhSeCH2Li led via 21 to 22 (Scheme 3). Once the OH group was protected (→ 22b), it proved possible to effect aldolization with crotonaldehyde (→ 23). Exposure of 23 to acid gave the sub-target compound 25. Its subsequent oxidation and thermal activation resulted in sequential selenoxide elimination with Claisen rearrangement (→ 26). The structural features of 26 require that a chair-like transition state be adopted during the [3.3]sigmatropic event. With the clarification of these issues, a highly serviceable and more advanced assault on the crenulatans should prove capable of being mounted.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19950780210
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