Total Synthesis of (±)- and (−)-Daphnillonin B
Yun-Peng Zou, Zheng-Lin Lai, Mengwei Zhang, Jianzhao Peng, Shuai Ning, Chuang‐Chuang Li
Abstract
The first total synthesis of (±)- and (−)-daphnillonin B, a daphnicyclidin-type alkaloid with a new [7-6-5-7-5-5] A/B/C/D/E/F hexacyclic core, has been achieved. The [6-5-7] B/C/D ring system was efficiently and diastereoselectively constructed via a mild type I intramolecular [5+2] cycloaddition, followed by a Grubbs II catalyst-catalyzed radical cyclization. The [5-5] fused E/F ring system was synthesized via a diastereoselective intramolecular Pauson–Khand reaction. Notably, the synthetically challenging [7-6-5-7-5-5] hexacyclic core was reassembled by a unique Wagner–Meerwein-type rearrangement from the [6-6-5-7-5-5] hexacyclic framework found in calyciphylline A-type Daphniphyllum alkaloids.