First total synthesis of β-carboline alkaloid trigonostemine G and its derivatives

Studies on the total syntheses of β‑carboline alkaloids orthoscuticellines A and B

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.

New Truxinic and Truxillic Acid Sucrose Diesters From the Leaves of Trigonostemon honbaensis

A new δ-truxinic acid sucrose diester and a new ε-truxillic acid sucrose diester (named trigohonbanosides E and F) were isolated from the leaves of Trigonostemon honbaensis. Their chemical structures were determined by extensive analysis of their HR-ESI-MS and NMR spectra. At a concentration of 20 µM, trigohonbanosides E and F exhibited weak inhibitory effects on NO production in LPS-activated RAW264.7 cells with inhibitory percentages of 22.7% ± 1.1% and 18.5% ± 1.4%, respectively.

Recent Advances in the Synthesis of β-Carboline Alkaloids

β-Carboline alkaloids are a remarkable family of natural and synthetic indole-containing heterocyclic compounds and they are widely distributed in nature. Recently, these alkaloids have been in the focus of interest, thanks to their diverse biological activities. Their pharmacological activity makes them desirable as sedative, anxiolytic, hypnotic, anticonvulsant, antitumor, antiviral, antiparasitic or antimicrobial drug candidates. The growing potential inherent in them encourages many researchers to address the challenges of the synthesis of natural products containing complex β-carboline frameworks. In this review, we describe the recent developments in the synthesis of β-carboline alkaloids and closely related derivatives through selected examples from the last 5 years. The focus is on the key steps with improved procedures and synthetic approaches. Furthermore the pharmacological potential of the alkaloids is also highlighted.