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Paper | Regular issue | Vol 36, No. 2, 1993, pp.345-358
Published online, 1st January, 1970
DOI: 10.3987/COM-92-6231
Furanoterpene Synthesis via Intramolecular Nitrile Oxide Cycloaddition Reaction: A Total Synthesis of (+)-Menthofuran

Kozo Shishido,* Koji Umimoto, Takeshi Takata, Osamu Irie, and Masayuki Shibuya

*Institute for Medicinal Resources, University of Tokushima, Sho-machi, Tokushima 770-8505, Japan


A fused furan assembling strategy based on an intramolecular [3+2] dipolar cycloaddition reaction of nitrile oxide has been applied to a total synthesis of perfumy furanomonoterpene (+)-menthofuran (1). The key cycloaddition substrates (9) and (12) are easily prepared via straightforward routes starting from (+)-citronellal and these are treated with sodium hypochlorite and p-chlorophenyl isocyanate, respectively. The cycloaddition reactions generate 10 : 1 mixture of diastereoisomeric isoxazolines (2a) and (2b) in good to excellent yields. The isoxazolines (2a,b) thus obtained are converted to (+)-menthofuran (1) by sequential reductive hydrolysis and alkaline hydrolysis (or vice versa) followed by acid treatment of the resulting β,γ-dihydroxy ketone (14).