Concise synthesis of the vasorelaxant alkaloids schwarzinicines A and B

Abstract

A concise synthesis of the 1,4-diarylbutanoid–phenethylamine alkaloids, schwarzinicines A (1) and B (2), recently isolated from Ficus schwarzii, is reported. Key steps include a Claisen condensation to assemble the 1,4-diaryl-2-butanone intermediate, followed by a reductive amination to furnish the core skeleton of the target compounds. The overall synthetic yields of 1 and 2 were 9.1% and 3.5%, respectively. Synthetic (−)-1, (+)-1 and (±)-1 exhibited comparable vasorelaxation as natural schwarzinicine A on rat isolated aortic rings, suggesting that the observed vasorelaxant effects were not influenced by the chirality at C-2.

Graphical Abstract

Keywords:

• Ficus schwarzii
• schwarzinicine
• phenethylamine
• alkaloid
• synthesis
• vasorelaxation

Conflict of interest

The authors have declared that there is no conflict of interest.

Additional information

Funding

This work was supported by MOHE Malaysia (FRGS/1/2017/STG01/UNIM/02/3 and FRGS/1/2017/SKK10/UNIM/01/1) and Malaysia Toray Science Foundation (TML-CA/17.195(17/G62)).