A facile and efficient diastereoselective synthesis of methyl 3β-hydroxyeudesmane-4,11(13)-dien-12-oicate starting from (+)-dihydrocarvone has been carried out in 9 steps at the first time.
The first total synthesis of （+）-5α-hydroxy-isopterocarpolone （1）, an oxygenated eudesmane isolated from Chinese folk medicine Artemisia eriopoda, starting from （+）-dihydrocarvone（2） was described. Compound 4 was stereoselectively prepared from compound 2 in three steps according to reference-. The treatment of tosylhydrazone 5, which was formed via the reaction of compound 4 and TsNHNH2 catalyzed by BF3-5Et2O, with an excess of n-butyllithium gave triene 6. Oxidation of triene 6 with singlet oxygen afforded the desired endo-peroxide 7 as a single product. Reductive cleavage of peroxide 7 with K2CO3 gave α-rotunol 3, a natural eudesmane firstly isolated in 1969. Hydrolysis of α-rotunol 3 with 10% sulfuric acid afforded （+）-5α-hydroxy-isopterocarpolone （1）. The structures of all the compounds were confirmed by IR, MS and NMR spectra.
The enantioselective total synthesis of 12 carboxyeudesma 3,11(13) diene(1) was achieved starting from(-) dihydrocarvone in ten steps for the first time. The key steps mainly include the introduction of hydroxyl group into C 12 position of eudesmane by Vilsmeier chlorination and the generation of C3-C4 double bond into the eudesmane skeleton by elimination of halide.
