Syntheses of new humulene derivatives; (2E,6E,9E)- and (2Z,6E,9E)-cycloundecatrienones, by intramolecular alkylation of protected cyanohydrin. A route to humulene

✍ Scribed by Takashi Takahashi; Kyoko Kitamura; Jiro Tsuji

• Publisher: Elsevier Science
• Year: 1983
• Tongue: French
• Weight: 261 KB
• Volume: 24
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)86230-9

✦ Synopsis

Hendrickson') reported a biogenetic hypothesis for bi-and tricyclic sesquiterpenes and suggested that cation _l and cation ,2, derived from trans-and cis-farnesyl pyrophosphate respectively, were the most important key intermediates in the biosynthesis of sesquiterpenes. On the other hand, Parker 2) suggested that one could obtain the C(7)-cation from humulene by the selective protonation of E-6A-olefin. So far many chemists have studied conversions of humulene and its derivatives, promoted by various acids, into bi-and tricyclic sesquiterpenes. However, most of these conversions were non-selective and gave many products. Recently Matsumoto') succeeded in the chemical conversions of humulene into naturally occurring tricyclic terpenes such as sterpurene, hirstene, and capnellene. These results suggest that the use of transannular cyclization of medium-ring compounds would be an interesting synthetic method for syntheses of the above mentioned tricyclic terpenes, if one could prepare the humulene derivatives, in which the selective activation of functional groups is possible, starting from easily available compounds. In this paper we wish to report syntheses of new humulene derivatives, (2E,6E,9E)-2,5,5,9-tetramethyl-2,6,9-cycloundecatrienone (4) and (22,6E,9E)-2,5,5,9-tetramethyl-2,6,9-cycloundecatrienone (16) based on the intramolecular alkylation4) of the protected cyanohydrin and the conversion of 4 to humulene (_3).

In our synthetic plan (Scheme 1) for the preparation of (2B,6E,9E)-trienone 4, the