Orthoscuticellines A and B are newly isolated natural β-carboline alkaloids from the moss animal Orthoscuticella ventricosa. Herein, we report the first targeted total synthesis of orthoscuticelline B and an analogous synthetic method for the preparation of dihydro derivate of orthoscuticelline A. The new synthetic approach is based on commercially available and inexpensive reagents leading to a practical synthesis of the target molecules. The reaction sequence consisting of a T3P®-catalyzed amide formation followed by a Bischler-Napieralski cyclisation and a DDQ-assisted dehydrogenation step ensures a practical access to orthoscuticelline B in three steps with 58% overall yield.
Keywords: Orthoscuticella ventricosa; alkaloids; orthoscuticelline A; orthoscuticelline B; orthoscuticellines; total synthesis; β‑carboline.