Simple Synthesis of Sakuranetin and Selinone via a Common Intermediate, Utilizing Complementary Regioselectivity in the Deacetylation of Naringenin Triacetate.

Sakuranetin and selinone were successfully synthesized utilizing the regioselective deacetylation of naringenin triacetate. Deacetylation of the latter at C-7 with imidazole in 1,4-dioxane at 40°C furnished the corresponding diacetate in 80% yield. Methylation of the obtained free hydroxy group and subsequent removal of the remaining two acetyl groups gave sakuranetin, which was previously isolated as a phytoalexin against rice blast disease fungus, Pyricularia oryzae, in 71% overall yield. The same intermediate, naringenin triacetate, was subjected to transesterification with 2-propanol in tetrahydrofuran, catalyzed by Candida antarctica lipase B. A contrasting regioselective preference for C-4' deacetylation was observed, giving an isomeric diacetate in 82% yield. Prenylation of the free hydroxy group under Mitsunobu conditions and subsequent deprotection furnished selinone, which was previously isolated from Monotes engleri and exhibits antifungal activity against Candida albicans, in 55% overall yield.