The synthesis of possible intermediates in the biogenesis of tetranortriterpenes by the conversion of the side-chain of turraeanthin into a β-substituted furan

Meliaceous Limonoids: Chemistry and Biological Activities

“…A possible key intermediate in the biosynthesis of the ring D-seco limonoids was synthesized by the conversion of the side-chain of turraeanthin, a protolimonoid in Turraeanthus africanus , into a β-substituted furan in two steps with considerable yield. , The tactics of the synthesis of fraxinellone ( 1142 ) included reaction of 6-formyl-2,6-dimethyl-cyclohex-2-enecarboxylates with furyl-lithium followed by double-bond isomerization with base, , and conversion from fraxinellonone ( 1141 ) in short steps . After formation of the five-membered lactone, an aldol reaction and olefin metathesis established the bicyclic ring system, in which the catalytic diastereoselective Oshima–Utimoto reaction was employed as key step (Scheme ) .…”