The role of the bifunctional catalyst is decisive: The magnesium ion as Lewis acid and its nucleophilic iodide counterion contribute in synergy to the successful ring expansion of the cyclopropane 1 by aldimine 2 [Eq. (1)]. This reaction offers a novel route to spiro[pyrrolidin‐3,3′‐oxindoles] 3.

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CLK2 inhibition has been proposed as a potential mechanism to improve autism and neuronal functions in Phelan-McDermid syndrome (PMDS). Herein, the discovery of a very potent indazole CLK inhibitor series and the CLK2 X-ray structure of the most potent analogue are reported. This new indazole series was identified through a biochemical CLK2 Caliper assay screen with 30k compounds selected by an in silico approach. Novel high-resolution X-ray structures of all CLKs, including the first CLK4 X-ray structure, bound to known CLK2 inhibitor tool compounds (e.g., TG003, CX-4945), are also shown and yield insight into inhibitor selectivity in the CLK family. The efficacy of the new CLK2 inhibitors from the indazole series was demonstrated in the mouse brain slice assay, and potential safety concerns were investigated. Genotoxicity findings in the human lymphocyte micronucleus test (MNT) assay are shown by using two structurally different CLK inhibitors to reveal a major concern for pan-CLK inhibition in PMDS.

An efficient synthesis of the antitumor alkaloid (+/-)-strychnofoline is documented. Key to the development of the highly convergent strategy delineated is the coupling of a cyclic imine with spiro[cyclopropan-1,3'-oxindole], which takes place in a highly diastereoselective manner. The ability to conduct annulation reactions of spirocyclopropyloxindoles with functionalized cyclic imines provides new avenues for the preparation of this important class of biologically active structures.

Studies aimed at preparing (+/-)-strychnofoline by total synthesis are detailed. The route described makes use of a recently developed MgI(2)-mediated ring-expansion reaction of spiro[cyclopropan-1,3'-oxindole] with a cyclic disubstituted aldimine. The ring-expansion product was formed as a single diastereoisomer in 55 % yield, possessing the same stereochemical pattern found in strychnofoline. In addition, our synthetic effort has led to the development of new reaction methodology to access 3,4-disubstituted cyclic aldimines.

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Ergoline derivative (6aR,9R)-4-(2-(dimethylamino)ethyl)-N-phenyl-9-(pyrrolidine-1-carbonyl)-6,6a,8,9-tetrahydroindolo[4,3-fg]quinoline-7(4H)-carboxamide (1), a CXCR3 antagonist, also inhibits human histamine H3 receptors (H3R) and represents a structurally novel H3R inverse agonist chemotype. It displays favorable pharmacokinetic and in vitro safety profiles, and served as a lead compound in a program to explore ergoline derivatives as potential drug candidates for the treatment of narcolepsy. A key objective of this work was to enhance the safety and efficacy profiles of 1, while minimizing its duration of action to mitigate the episodes of insomnia documented with previously reported clinical candidates during the night following administration. Modifications to the ergoline core at positions 1, 6 and 8 were systematically investigated, and derivative 23 (1-((4aR,8R,9aR)-8-(hydroxymethyl)-1-(2-((R)-2-methylpyrrolidin-1-yl)ethyl)-4,4a,7,8,9,9a-hexahydroindolo[1,14-fg]quinolin-6(1H)-yl)ethanone) was identified as a promising lead compound. Derivative 23 has a desirable pharmacokinetic profile and demonstrated efficacy by enhancing brain concentrations of tele-methylhistamine, a major histamine metabolite. This validates the potential of the ergoline scaffold to serve as a template for the development of H3R inverse agonists.