A new and versatile synthetic route to Securinega alkaloids is reported. The first synthesis of allosecurinine has been accomplished in seven steps and 40% yield, starting from (+)-menisdaurilide, using a vinylogous Mannich reaction as the key transformation. Similarly, viroallosecurinine has been synthesized from (-)-menisdaurilide.

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Alkaloids U 0600Diastereoselective Synthesis of Allosecurinine (III) and Viroallosecurinine from Menisdaurilide. -The title compound is prepared in 42% overall yield starting from (+)-menisdaurilide (I). Following the same sequence, its enantiomer viroallosecurinine is available from (-)-(I). -(BARDAJI, G. G.; CANTO, M.; ALIBES, R.; BAYON, P.; BUSQUE*, F.; DE MARCH*, P.; FIGUEREDO, M.; FONT, J.; J.

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The natural products (-)-dihydromenisdaurilide, (-)-3, and (+)-dihydroaquilegiolide, (+)-4, were isolated in 1993, but synthetic reports related to these compounds are quite scarce. Only a synthesis of both natural isomers in enantioenriched form and a synthesis in enantiopure form of unnatural 3 and natural 4 have been reported. Starting from an enantiopure monoketal of pbenzoquinone, we have investigated several synthetic approaches to both lactones in enantiomerically pure form, but each of them resulted in racemization. Finally, partial hydrogenation of (+)-and (-)-menisdaurilide allowed the preparation of (+)-and (-)-dihydromenisdaurilide, respectively, and a Mitsunobu reaction applied to 3 afforded (+)-and (-)-dihydroaquilegiolide.