An intramolecular diels-alder approach to quassinoids—a stereoselective construction of a-aromatic klaineanone

✍ Scribed by Keiichiro Fukumoto; Masatoshi Chihiro; Yuichi Shiratori; Masataka Ihara; Tetsuji Kametani; Toshio Honda

• Book ID: 104220980
• Publisher: Elsevier Science
• Year: 1982
• Tongue: French
• Weight: 264 KB
• Volume: 23
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)87509-7

✦ Synopsis

Thermolysis of a benzocyclobutene derivative (20) prepared from norcamphor produced stereoselectively a tetracyclic compound (z), which was converted to a lactone (21) having correct stereochemistry at C7, C8, Cg, Cll, Cl3, and Cl4 positions of (f)-klaineanone. Quassinoids are highly oxygenated degraded triterpenes found in plants of Simaroubaceae. Recent extensive work on this group is mainly attributed to the potent antileukemic activity of the C15-acyloxylated derivatives such as bruceantin, reported by Kupchan et al. 2 Furthermore the oxygen functionality present in quassinoids coupled with its complicated stereostructure has stimulated a great deal of synthetic activity. Recently Grieco and coworkers elegantly synthesized (?)-quassin by employing intermolecular Diels-Alder strategy. 3 We had investigated synthesis of this type of terpene by thermolysis of benzocyclobutene derivatives. 495 In further con-