One-pot N-arylation of indoles directly from N-arylsulfonylindoles via consecutive deprotection and S(N)Ar Reactions with activated Aryl halides

Synthesis of Differentially Protected Azatryptophan Analogs via Pd2(dba)3/XPhos Catalyzed Negishi Coupling of N-Ts Azaindole Halides with Zinc Derivative from Fmoc-Protected tert-Butyl (R)-2-Amino-3-iodopropanoate

Unnatural amino acids play an important role in peptide based drug discovery. Herein, we report a class of differentially protected azatryptophan derivatives synthesized from N-tosyl-3-haloazaindoles 1 and Fmoc-protected tert-butyl iodoalanine 2 via a Negishi coupling. Through ligand screening, Pd₂(dba)₃/XPhos was found to be a superior catalyst for the coupling of 1 with the zinc derivative of 2 to give tert-butyl (S)-2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)-3-(1-tosyl-1H-pyrrolo[2,3-b]pyridin-3-yl)propanoate derivatives 3 in 69-91% isolated yields. In addition, we have demonstrated that the protecting groups, namely, Ts, Fmoc, and ^tBu, can be easily removed selectively.

Design, Synthesis and Biological Evaluation of 7-Chloro-9H-pyrimido[4,5-b]indole-based Glycogen Synthase Kinase-3β Inhibitors

Glycogen synthase kinase-3β (GSK-3β) represents a relevant drug target for the treatment of neurodegenerative pathologies including Alzheimer's disease. We herein report on the optimization of a novel class of GSK-3β inhibitors based on the tofacitinib-derived screen hit 3-((3R,4R)-3-((7-chloro-9H-pyrimido[4,5-b]indol-4-yl)(methyl)amino)-4-methylpiperidin-1-yl)-3-oxopropanenitrile (1). We synthesized a series of 19 novel 7-chloro-9H-pyrimido[4,5-b]indole-based derivatives and studied their structure-activity relationships with focus on the cyanoacetyl piperidine moiety. We unveiled the crucial role of the nitrile group and its importance for the activity of this compound series. A successful rigidization approach afforded 3-(3aRS,7aSR)-(1-(7-chloro-9H-pyrimido[4,5-b]indol-4-yl)octahydro-6H-pyrrolo[2,3-c]pyridin-6-yl)-propanenitrile (24), which displayed an IC₅₀ value of 130 nM on GSK-3β and was further characterized by its metabolic stability. Finally, we disclosed the putative binding modes of the most potent inhibitors within the ATP binding site of GSK-3β by 1 µs molecular dynamics simulations.

Synthesis of benzopyrano[4,3-b](N-arylsulfonyl)indoles and benzopyrano[3,4-b](N-arylsulfonyl)indoles via intramolecular palladium-catalyzed aryl-aryl coupling reaction

A series of benzopyrano[3,4-b](N-arylsulfonyl) indole derivatives and benzopyrano[4,3-b](N-arylsulfonyl) indole derivatives were synthesized from 2- or 3-methylindole via intermolecular S( N )2 reaction and subsequent intramolecular palladium-catalyzed aryl-aryl coupling reaction for the first time. It was suggested that, besides using the Fischer cyclization, benzopyrano[4,3-b]indoles and benzopyrano[3,4-b]indoles could also be prepared via intermolecular S( N )2 reaction and sequential intramolecular palladium-catalyzed coupling reaction.