Total Synthesis of (+)-Chimonanthine, (+)-Folicanthine, and (−)-Calycanthine
journal contributionposted on 16.10.2015 by Ming Ding, Kangjiang Liang, Rui Pan, Hongbin Zhang, Chengfeng Xia
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Facile, straightforward, and asymmetric total syntheses of (+)-chimonanthine (1), (+)-folicanthine (2), and (−)-calycanthine (3) were accomplished in four to five steps from commercially available tryptamine. The synthesis features copper-mediated asymmetric cyclodimerization of chiral tryptamine derivative, which established a new entry into constructing the sterically hindered vicinal quaternary stereogenic carbon centers of dimeric hexahydropyrroloindole alkaloids in one procedure. An unprecedented base-induced isomerization from the chimonanthine skeleton to the calycanthine skeleton was observed and facilitated the synthesis of (−)-calycanthine (3).