41 植物生長制御物質GA_<12>,GA_<111>およびGA_<112>の全合成(口頭発表の部)

抄録

The gibberellins, plant growth regulators, are divided into two groups, the larger of which is C_<19> gibberellins [gibberellic acid: GA_3 (1) is a typical representative] and most of the remaining have 20 carbons. The latter possess the ent-gibberellane carbon skeleton. GA_<12> (2), GA_<111> (3), and GA_<112> (4) belong to C_<20> gibberellins and 2 is presumed to be a common intermediate in the biosynthesis of all gibberellins. A significant array of biological activities and structural complexity have made gibberellins popular targets for total synthesis. Although GA_3 (1) is produced commercially by the large-scale fermentation of the fungus Gibberella fujikuroi, most of the C_<20> gibberellin syntheses have been achieved through many functional group manipulations, in spite of starting with tricyclic compounds or natural gibberellins. An efficient synthetic route to C_<20> gibberellins would make it possible to confirm tentative new structures and to explore their biological activities. Herein we would like to present novel synthetic routes to C_<20> by a radical cyclization, and by a combination of palladium-catalyzed cycloalkenylation reaction and reverse electron demand intramolecular Diels-Alder reaction.