Robert K. Orr

Enantioselective Synthesis of α-Methyl-β-cyclopropyldihydrocinnamates

α- and β-substitution of dihydrocinnamates has been shown to increase the biological activity of various drug candidates. Recently, we identified enantio- and diastereopure α-methyl-β-cyclopropyldihydrocinnamates to be important pharmacophores in one of our drug discovery programs and endeavored to devise an asymmetric hydrogenation strategy to improve access to this valuable framework. We used high throughput experimentation to define stereoconvergent Suzuki-Miyaura cross-coupling conditions affording (Z)-α-methyl-β-cyclopropylcinnamates and subsequent ruthenium-catalyzed asymmetric hydrogenation conditions affording the desired products in excellent enantio- and diastereoselectivities. These conditions were executed on multigram to kilogram scale to provide three key enantiopure α-methyl-β-cyclopropyldihydrocinnamates with high selectivity.

Development of a palladium-catalyzed α-arylation of cyclopropyl nitriles.

1,1-Disubstituted aryl cyclopropyl nitriles are useful moieties in biologically active compounds and provide access to a range of cyclopropyl derivatives. Herein, we describe the development of a palladium-catalyzed α-arylation of cyclopropyl, cyclobutyl, and cyclopentyl nitriles that affords these functional groups in one step from a variety of aryl bromides in good to excellent yields. Furthermore, we demonstrate the transformation of aryl cyclopropyl nitriles into aryl trifluoromethyl cyclopropanes.

Development of a novel tricyclic class of potent and selective FIXa inhibitors.

Using structure based drug design, a novel class of potent coagulation factor IXa (FIXa) inhibitors was designed and synthesized. High selectivity over FXa inhibition was achieved. Selected compounds were evaluated in rat IV/PO pharmacokinetic (PK) studies and demonstrated desirable oral PK profiles. Finally, the pharmacodynamics (PD) of this class of molecules were evaluated in thrombin generation assay (TGA) in Corn Trypsin Inhibitor (CTI) citrated human plasma and demonstrated characteristics of a FIXa inhibitor.

Development of a novel class of potent and selective FIXa inhibitors

Using structure based drug design (SBDD), a novel class of potent coagulation Factor IXa (FIXa) inhibitors was designed and synthesized. High selectivity over FXa inhibition was achieved. Selected compounds demonstrated oral bioavailability in rat IV/PO pharmacokinetic (PK) studies. Finally, the pharmacodynamics (PD) of this class of molecules was evaluated in Thrombin Generation Assay (TGA) in Corn Trypsin Inhibitor (CTI) citrated human plasma and demonstrated characteristics of a FIXa inhibitor.

Design and Synthesis of Novel, Selective GPR40 AgoPAMs

GPR40 is a G-protein-coupled receptor expressed primarily in pancreatic islets and intestinal L-cells that has been a target of significant recent therapeutic interest for type II diabetes. Activation of GPR40 by partial agonists elicits insulin secretion only in the presence of elevated blood glucose levels, minimizing the risk of hypoglycemia. GPR40 agoPAMs have shown superior efficacy to partial agonists as assessed in a glucose tolerability test (GTT). Herein, we report the discovery and optimization of a series of potent, selective GPR40 agoPAMs. Compound 24 demonstrated sustained glucose lowering in a chronic study of Goto Kakizaki rats, showing no signs of tachyphylaxis for this mechanism.

Synthesis of the γ-Secretase Modulator MK-8428

The synthesis of the γ-secretase modulator MK-8428 (1) is described. The synthesis is highlighted by an enzyme-catalyzed reaction to access 3,4,5-trifluoro-(S)-phenylglycine, a 1-pot activation/displacement/deprotection sequence to introduce the aminooxy functionality and a dehydrative intramolecular cyclization under mild conditions to form the oxadiazine heterocycle of 1. In situ reaction monitoring was employed to understand the deleterious role of water during the formation of a methanesulfonate ester in the 1-pot activation/displacement/deprotection sequence.

Structure–Activity Relationship of Novel and Selective Biaryl-Chroman GPR40 AgoPAMs

A series of biaryl chromans exhibiting potent and selective agonism for the GPR40 receptor with positive allosteric modulation of endogenous ligands (AgoPAM) were discovered as potential therapeutics for the treatment of type II diabetes. Optimization of physicochemical properties through modification of the pendant aryl rings resulted in the identification of compound AP5, which possesses an improved metabolic profile while demonstrating sustained glucose lowering.

New reactions and processes for the efficient synthesis of a HCV NS5b prodrug

Herein we describe the route scouting and process development efforts toward a green and sustainable synthesis of the HCV NS5b cyclic prodrug nucleoside (CPN) 1. Through the discovery and development of a crystallization-induced dynamic resolution and a novel chemo- and stereo-selective phosphorylation reaction, we eliminated costly chromatographies and protecting group manipulations utilized in the initial approaches to this compound and implemented a highly streamlined and sustainable approach to the target molecule. We demonstrate how these improvements impact the PMI of the API on the kilogram scale and compare our work to the PMI of APIs of similar complexity.

Discovery of phenyl acetamides as potent and selective GPR119 agonists

The paper describes the SAR/SPR studies that led to the discovery of phenoxy cyclopropyl phenyl acetamide derivatives as potent and selective GPR119 agonists. Based on a cis cyclopropane scaffold discovered previously, phenyl acetamides such as compound 17 were found to have excellent GPR119 potency and improved physicochemical properties. Pharmacokinetic data of compound 17 in rat, dog and rhesus will be described. Compound 17 was suitable for QD dosing based on its predicted human half-life, and its projected human dose was much lower than that of the recently reported structurally-related benzyloxy compound 2. Compound 17 was selected as a tool compound candidate for NHP (Non-Human Primate) efficacy studies.

Development of a stereoselective and scalable process for the preparation of a methylcyclobutanol-pyridyl ether

The evolution of a scalable process for the preparation of methylcyclobutanol-pyridyl ether 1 is described. Key aspects of this development including careful control of the stereochemistry, elimination of chromatography, and application to kilogram-scale synthesis are addressed.