多官能性天然生理活性物質の全合成 大環状ピロリチジンアルカロイドの合成

Abstract

Synthetic studies on the macrocyclic pyrrolizidine alkaloids are described.Racemic retronecine 9 and otonecine 10 were synthesized from a common and key intermediate 15. Optically active retronecine 9 was synthesized enantioselectively from (R) - (+) -malic acid 27. An efficient enantioselective synthesis of the N- (ethoxycarbonyl) methyl Geissman-Waiss lactone 39 was achieved from (R) - (+) -malic acid 27, providing a practical synthetic route to optically active retronecine 9.Dicrotaline 6, an 11-membered pyrrolizidine alkaloid was synthesized by virtue of a newly developed method using the stannylene 64.Total synthesis of optically active integerrimine 7, a representative of the 12-membered pyrrolizidine alkaloids was achieved as follows : Optically active integerrinecic acid derivative 80 synthesized enantioselectively from (E) -2-methylhepta-2, 6-dienoic acid 74 was converted to the cyclic anhydride 82. Reaction of the cyclic anhydride 82 with the stannylene 64 gave the desired monoester 83 regioselectively. Lactonization of the monoester 83 by the Yamaguchi's method provided integerrimine MTM ether 84, which was converted to (-) -integerrimine 7.