Key points are not available for this paper at this time.
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.
Ataka et al. (2023) studied this question.