25 分解リモノイドの合成的研究

抄録

Studies directed to the total syntheses of several degraded limonoids will be presented in this lecture. Fraxinellone 1 has been synthesized by the condensation of 3-furyl lithium with 1-carbethoy-2-formyl-2,6-dimethyl-5-cyclohexene 11, which is prepared through Diels-Alder reaction between ethyl 3-methyl-2,4-pentadienoate and methacrolein and the following isomerisation of the double bond. In the synthesis of pyroangolensolide 6, the key intermediate 34 was produced from 4,8-dimethylhexahydro-3(9)-inden-2-one 21, which was prepared through Wichterle annelation of 2,6-dimethylcyclohexanone. The reaction of 34 with 3-furyl lithium affords pyroangolensolide 6 together with its diastereomer 36. The synthetic approach to calodendrolide 3 starts from 4,8-dimethylhexa-hydro-3(9)-inden-2-one 21, the same intermediate as in the synthesis of pyroangolensolide 6. The diepoxide intermediate 49, which posses 3,9-epoxide ring with the correct stereochemistry and the appropriate functionalities for further elaboration, has been derived.