北島 満里子

The first enantioselective total synthesis of kopsiyunnanine B, which has a unique folded and complex pentacyclic structure containing six contiguous chiral centers, has been achieved along our originally proposed biosynthetic pathway. The key reaction of this synthesis includes a bioinspired cascade that builds three ring structures and three chiral centers in one step and features the stereoselective reduction of a β-acrylate and oxidation to an oxindole.

The enantioselective total syntheses of (-)-silicine and (-)-20-episilicine, which contain a chiral piperidine with three contiguous chiral centers (D-ring) and a strained seven-membered ring (C-ring) attached to an indole, were achieved. The key steps of these syntheses included a chiral secondary amine-catalyzed formal aza-[3 + 3] cycloaddition reaction and Lewis acid-mediated irreversible ring-closing reaction. In addition, the stereochemistry at C20 was controlled at a later stage in the syntheses.