Enantioselective synthesis of R-(−)-ligularenolide starting from S-(+)-carvone

Total Synthesis of the Sesquiterpenoid Periconianone A Based on a Postulated Biogenesis

“…No conversion of the starting material was observed at lower reaction temperatures, whereas higher temperatures led to increased formation of the undesired diastereoisomer. Lewis acid-catalyzed Michael addition of TMS enol ether 4 to methyl vinyl ketone in the presence of BF 3 ·OEt 2 gave the desired diketone 5 in 66% yield, together with desilylated starting material, which was recycled. The isopropenyl group at C2 had by now served its role to establish the stereogenic centers at C4 and C5 and was therefore cleaved by Criegee fragmentation: ozonolysis of the terminal double bond in 5 and subsequent treatment of the formed peroxy acetal intermediate with Cu­(OAc) 2 and FeSO 4 triggered the fragmentation to yield enone 6 .…”

Natural cyclic α, β-enone monoterpenoids in nucleophilic addition reactions

“…However, the formation of a mixture (1:10) of diastereomeric diketones prepared by Wacker oxidation of the double bond in oxodiene 131 was observed [55,56]. Ketone 145 was used as a substrate in the synthesis of optically pure natural compounds [58][59][60][61][62][63], for example, to prepare clerodanes, namely dihydroclerodane (147) and lupulin C (148), diterpenoids with broad spectra of biological activity (antiviral, antiseptic, antitumor, antiulcer, etc.) The second ring was constructed by intramolecular Robinson annelation.…”

Natural sesquiterpenoids

“…273 (+)-(S)-Carvone has been used as starting material in an enantioselective synthesis of ( 2)-(R)-ligularenolide. 274 Five novel bioactive sesquiterpenes 12-hydroxychiloscyphone 277, chiloscypha-2,7-dione 278, 12-hydroxychiloscypha-2,7-dione 279, chiloscypha-2,7,9-trione 280 and rivulalactone 281 have been obtained from Chiloscyphus rivularis. 275…”