29 フラノテルペン類の合成研究(ポスター発表の部)

概要

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Development of a novel and flexible method for the construction of 2,3-disubstituted, 2,3,4- and 2,3,5-trisubstiruted, and 2,3,4,5-tetrasubstituted fused furans and its application to the synthesis of furanoterpenoids have been demonstrated. The key strategic element of the method involves the intramolecular [3+2] dipolar cycloaddition reaction of the nitrite oxide (1) to furnish the isoxazoline (2), which is exposed to the conditions for reductive hydrolysis followed by treatment of the crude reaction product with p-toluenesulfonic acid. The reaction leads to the formation of a variety of fused furans (4) and their regioisomers in moderate or good yields. Employing this methodology, total syntheses of (+)-pallescensin A (16) and (+)-menthofuran (58) have been accomplished. Furthermore, the left half segment (30), containing fused furan and diene moieties, of hippospongin (okinonellin A) (20) has been synthesized by using the Yamamoto rearrangement for an elaboration of the chiral quaternary carbon center presented. The construction of BCD ring system (47) of the tanshinones has also been demonstrated.
天然有機化合物討論会の論文
1991-09-07