1 新規環変換反応の開発と二、三の天然物合成への応用(口頭発表の部)

概要

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A new method of ring transformation has been developed. As shown in Table 1, treatment of 3-(3-oxoalkyl)cyclopentanones with BF_3-Et_2O and ethylene glycol afforded the ring transformed products. Cyclopentanones with carbonyl function at the α-side chain underwent a facile ring expansion under the same reaction conditions (Table 2). The ring-transformation reaction of hydropentalenes provided us a new strategy for construction of bridgehead, spiro, and hydroazulene skeletons (Table 3). The process of this "one-pot" ring transformation is tentatively proposed to involve three steps of aldol condensation, acetalization, and Grob fragmentation. This method has been applied to the syntheses of (dl)-trichodiene and (dl)-acorenone B. By using a similar ring fragmentation reaction to the ring-enlarged lactone (28) from intramolecular acetal (27b), synthesis of (R)-(-)-phoracantholide I has been successfully achieved.
天然有機化合物討論会の論文
1991-09-07