20 Δ^<9(12)>-カプネレン-8β,10α-ジオール及び、Δ^<9(12)>-カプネレン-3β,8β,10α-トリオールの全合成
詳細
The first achievement of total syntheses of two marine sesquiterpenes, (±)-Δ^<9(12)>-capnellene-8β,10α-diol(1) and (±)-Δ^<9(12)>-capnellene-3β,8β,10α-triol(3) will be disclosed. In the first place the efficient syntheses of the two key intermediate 16 and 21 corresponding to the AB-rings of the two sesquiterpenes will be presented. The synthesis utilized the common intermediate 12 easily produced from the silyl enol ether 10 by Saegusa-Ito reaction. Interestingly treatment of 12 with DBU in refluxing benzene gave 13 exclusively. In the second place the construction of the ABC-ring corresponding to 1 will be discussed. As expected, the aldol condensation of 23 under a variety of the reaction conditions provided only a trace amount of the desired product. However, this difficulty was nicely overcome by utilizing organosilicon chemistry. Namely treatment of 23 with TMSOTf-NEt_3 in refluxing benzene gave the desired product 24 in 40% yield together with the recovery of 23 30%. In the third place accomplishment of (±)-Δ^<9(12)>-capnellene-8β,10α-diol(1) via the triol 31 will be presented. In contrast to the triol route the allylsilane route shown in schemeV provided the stereoisomer 29, whose x-ray analysis is now under way. In the last place, according to the reaction sequence developed in the total synthesis of(±)-1, transformation of 21 to (±)-Δ^<9(12)>-capnellene-3β,8β,10α-triol(3) will be discussed.
