Issue 63, 2020

Bifunctional thiosquaramide catalyzed asymmetric reduction of dihydro-β-carbolines and enantioselective synthesis of (−)-coerulescine and (−)-horsfiline by oxidative rearrangement

Abstract

Tetrahydro-β-carboline (THBC) is a tricyclic ring system that can be found in a large number of bioactive alkaloids. Herein, we report a simple and efficient method for the synthesis of enantiopure THBCs through a chiral thiosquaramide (11b) catalyzed imine reduction of dihydro-β-carbolines (17a–f). The in situ generated Pd–H employed as hydride source in the reaction of differently substituted chiral THBCs (18a–f) afforded high selectivities (R isomers, up to 96% ee) and good isolated yields (up to 88%). Moreover, the chiral thiosquaramide used also afforded exceptional catalyst activity in the syntheses of (−)-coerulescine (5) and (−)-horsfiline (6) with excellent enantioselectivities up to 98% and 93% ee, respectively, via an enantioselective oxidative rearrangement approach.

Graphical abstract: Bifunctional thiosquaramide catalyzed asymmetric reduction of dihydro-β-carbolines and enantioselective synthesis of (−)-coerulescine and (−)-horsfiline by oxidative rearrangement

Supplementary files

Article information

Article type
Paper
Submitted
08 ก.ย. 2563
Accepted
15 ต.ค. 2563
First published
21 ต.ค. 2563
This article is Open Access
Creative Commons BY-NC license

RSC Adv., 2020,10, 38672-38677

Bifunctional thiosquaramide catalyzed asymmetric reduction of dihydro-β-carbolines and enantioselective synthesis of (−)-coerulescine and (−)-horsfiline by oxidative rearrangement

M. Sathish, F. M. Nachtigall and L. S. Santos, RSC Adv., 2020, 10, 38672 DOI: 10.1039/D0RA07705D

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