The Synthesis of Methyl-Substituted Spirocyclic Piperidine-Azetidine (2,7-Diazaspiro[3.5]nonane) and Spirocyclic Piperidine-Pyrrolidine (2,8-Diazaspiro[4.5]decane) Ring Systems.

The synthesis of a series of pharmaceutically important N-protected methyl-substituted spirocyclic piperidine-azetidine (2,7-diazaspiro[3.5]nonane) and spirocyclic piperidine-pyrrolidine (2,8-diazaspiro[4.5]decane) ring systems was developed. These motifs contain two differentiated sites (protected secondary amines) to allow for further functionalization via reductive amination, amidation, or other chemistry. The methyl-substituted spiroazetidine ring systems were accessed using nitrile lithiation/alkylation chemistry while the methyl-substituted spiropyrrolidines were synthesized by 1,4-addition reactions with nitroalkanes, followed by reduction and cyclization. These conditions were then scaled for the synthesis of 1-methyl spirocyclic piperidine-pyrrolidine with a classical resolution of the product using a tartaric acid derivative to isolate a single enantiomer.

Discovery of spirocyclic-diamine inhibitors of mammalian acetyl CoA-carboxylase.

A novel series of spirocyclic-diamine based, isoform non-selective inhibitors of acetyl-CoA carboxylase (ACC) is described. These spirodiamine derivatives were discovered by design of a library to mimic the structural rigidity and hydrogen-bonding pattern observed in the co-crystal structure of spirochromanone inhibitor I. The lead compound 3.5.1 inhibited de novo lipogenesis in rat hepatocytes, with an IC50 of 0.30 µM.

Decreasing the rate of metabolic ketone reduction in the discovery of a clinical acetyl-CoA carboxylase inhibitor for the treatment of diabetes.

Acetyl-CoA carboxylase (ACC) inhibitors offer significant potential for the treatment of type 2 diabetes mellitus (T2DM), hepatic steatosis, and cancer. However, the identification of tool compounds suitable to test the hypothesis in human trials has been challenging. An advanced series of spirocyclic ketone-containing ACC inhibitors recently reported by Pfizer were metabolized in vivo by ketone reduction, which complicated human pharmacology projections. We disclose that this metabolic reduction can be greatly attenuated through introduction of steric hindrance adjacent to the ketone carbonyl. Incorporation of weakly basic functionality improved solubility and led to the identification of 9 as a clinical candidate for the treatment of T2DM. Phase I clinical studies demonstrated dose-proportional increases in exposure, single-dose inhibition of de novo lipogenesis (DNL), and changes in indirect calorimetry consistent with increased whole-body fatty acid oxidation. This demonstration of target engagement validates the use of compound 9 to evaluate the role of DNL in human disease.

Spirolactam-based acetyl-CoA carboxylase inhibitors: toward improved metabolic stability of a chromanone lead structure.

Acetyl-CoA carboxylase (ACC) catalyzes the rate-determining step in de novo lipogenesis and plays a crucial role in the regulation of fatty acid oxidation. Alterations in lipid metabolism are believed to contribute to insulin resistance; thus inhibition of ACC offers a promising option for intervention in type 2 diabetes mellitus. Herein we disclose a series of ACC inhibitors based on a spirocyclic pyrazololactam core. The lactam series has improved chemical and metabolic stability relative to our previously reported pyrazoloketone series, while retaining potent inhibition of ACC1 and ACC2. Optimization of the pyrazole and amide substituents led to quinoline amide 21, which was advanced to preclinical development.

Identification of novel series of pyrazole and indole-urea based DFG-out PYK2 inhibitors.

Previous drug discovery efforts identified classical PYK2 kinase inhibitors such as 2 and 3 that possess selectivity for PYK2 over its intra-family isoform FAK. Efforts to identify more kinome-selective chemical matter that stabilize a DFG-out conformation of the enzyme are described herein. Two sub-series of PYK2 inhibitors, an indole carboxamide-urea and a pyrazole-urea have been identified and found to have different binding interactions with the hinge region of PYK2. These leads proved to be more selective than the original classical inhibitors.

Synthesis of spiropiperidine lactam acetyl-CoA carboxylase inhibitors.

The synthesis of 4',6'-dihydrospiro[piperidine-4,5'-pyrazolo[3,4-c]pyridin]-7'(2'H)-one-based acetyl-CoA carboxylase inhibitors is reported. The hitherto unknown N-2 tert-butyl pyrazolospirolactam core was synthesized from ethyl 3-amino-1H-pyrazole-4-carboxylate in a streamlined 10-step synthesis requiring only one chromatography procedure. The described synthetic strategy provides pyrazolo-fused spirolactams from halogenated benzylic arenes and cyclic carboxylates. Key steps include a regioselective pyrazole alkylation providing the N-2 tert-butyl pyrazole and a Curtius rearrangement under both conventional and flow conditions to install the hindered amine via a stable and isolable isocyanate. Finally, a Parham-type cyclization was used to furnish the desired spirolactam. An analogous route provided efficient access to the related N-1 isopropyl lactam series. Elaboration of the lactam cores via amidation enabled synthesis of novel ACC inhibitors and the identification of potent analogues.

Synthesis of 7-oxo-dihydrospiro[indazole-5,4'-piperidine] acetyl-CoA carboxylase inhibitors.

Synthesis of oxo-dihydrospiroindazole-based acetyl-CoA carboxylase (ACC) inhibitors is reported. The dihydrospiroindazoles were assembled in a regioselective manner in six steps from substituted hydrazines and protected 4-formylpiperidine. Enhanced regioselectivity in the condensation between a keto enamine and substituted hydrazines was observed when using toluene as the solvent, leading to selective formation of 1-substituted spiroindazoles. The 2-substituted spiroindazoles were formed selectively from alkyl hydrazones by ring closure with Vilsmeier reagent. The key step in the elaboration to the final products is the conversion of an intermediate olefin to the desired ketone through elimination of HBr from an O-methyl bromohydrin. This methodology enabled the synthesis of each desired regioisomer on 50-75 g scale with minimal purification. Acylation of the resultant spirocyclic amines provided potent ACC inhibitors.

Metabolism-guided design of short-acting calcium-sensing receptor antagonists.

As part of a strategy to deliver short-acting calcium-sensing receptor (CaSR) antagonists, the metabolically labile thiomethyl functionality was incorporated into the zwitterionic amino alcohol derivative 3 with the hope of increasing human clearance through oxidative metabolism, while delivering a pharmacologically inactive sulfoxide metabolite. The effort led to the identification of thioanisoles 22 and 23 as potent and orally active CaSR antagonists with a rapid onset of action and short pharmacokinetic half-lives, which led to a rapid and transient stimulation of parathyroid hormone in a dose-dependent fashion following oral administration to rats. On the basis of the balance between target pharmacology, safety, and human disposition profiles, 22 and 23 were advanced as clinical candidates for the treatment of osteoporosis.

Synthesis and SAR of 1,2,3,4-tetrahydroisoquinolin-1-ones as novel G-protein-coupled receptor 40 (GPR40) antagonists.

The development of a series of novel 1,2,3,4-tetrahydroisoquinolin-1-ones as antagonists of G protein-coupled receptor 40 (GPR40) is described. The synthesis, in vitro inhibitory values for GPR40, in vitro microsomal clearance and rat in vivo clearance data are discussed. Initial hits displayed high rat in vivo clearances that were higher than liver blood flow. Optimization of rat in vivo clearance was achieved and led to the identification of 15i, whose rat oral pharmacokinetic data is reported.