OXONIUM ION ELECTROPHILES - SYNTHESIS OF THE HYPOTENSIVE OUDENONE

The hypotensive oudenone (1) has been synthesized through the intermediacy of oxonium ion 4. Acid-catalyzed C-alkylation of 1,3-cyclopentanedione (3) with 5-poropyltetrahydro-2-furanol (6b) afforded dihydrooudenone 2b. In contrast, alkylation of 3 with 2-chloro-5-propyltetrahydrofuran (7b) was unsuccessful. Unsaturation was introduced into 2b by treatment with N-(phenylthio) succinimide to produce 10 followed by oxidation to the corresponding sulfoxide and elimination of phenylsulfenic acid, which produced oudenone (1).