Synthesis and Biological Evaluation of Cremastrine and an Unnatural Analogue

Tetrahedron Lett. 2012 Jul 11;53(28):3577-3580. doi: 10.1016/j.tetlet.2012.05.009. Epub 2012 May 10.

Abstract

In this Letter, we describe the first total synthesis of cremastrine, a pyrrolizidine alkaloid from Cremastra appendiculata, with anticholinergic activity as well as an unnatural analogue. The streamlined synthesis proceeds in 9 steps, 7 steps longest linear sequence, in 25.2% overall yield, and features novel methodology to construct the pyrrolizidine core. Biological evaluation of cremastrine and the unnatural analogue indicated that both are pan-mAChR functional antagonists.