4 Pd^<2+>-Promoted Cycloalkenylation反応による(±)-Hirsutene及び(±)-Stemodinの全合成(口頭発表の部)

抄録

Although the palladium-promoted cycloalkenylation reaction of an olefinic silyl enol ether is a powerful strategy for construction of polycyclic system, little is known about successful application of the above reaction to biologically active natural product syntheses. Herein we report the total syntheses of (±)-hirsutene (4) and (±)-stemodin (18) using diastereoselective palladium-promoted cycloalkenylation reaction. (I) Total Synthesis of (±)-Hirsutene (4) A sequence leading from trans-6-methyl-3-cyclohexenecarboxylic acid (6) to the cis, anti, cis linear triquinane hirsutene (4) is described in which the key step utilizes an acid catalyzed intramolecular conjugate addition (8→9a) and a Pd^<2+>-promoted highly stereocontrolled cyclization (10→12). (II) Total Synthesis of (±)-Stemodin (18) Intramolecular Diels-Alder reaction of the triene (24) and Pd^<2+>-promoted cyclization reaction of the olefinic silyl enol ether of 29 have been utilized as the key steps for a conceptually new, highly diastereocontrolled formal total synthesis of (±)-stemodin (18).