A Disconnection for Rapid Access to Heterocyclic Benzylic Amines with Fully Substituted α-Carbons.

2- or 4-Pyridyl benzylic amines represent a privileged motif in drug discovery. However, the formation of heterocyclic benzylic amines with fully substituted α-carbons can require the execution of lengthy synthetic routes, which limit their application. Addition of various nucleophilic agents to Ellman's imines has been well established; however, there is no precedented literature reported for pyridyl-type nucleophiles, which are very important for medicinal chemistry. In this letter, we disclose the development of a one-step synthesis of heterocyclic benzylic amines with fully substituted α-carbons from heteroaryl halides and sulfinyl imines. Starting from 2,4-dibromopyridine, regioselective synthesis of 2- or 4-pyridyl benzylic amines could be achieved by choosing toluene or MTBE as a solvent.

Synthesis of Small 3-Fluoro- and 3,3-Difluoropyrrolidines Using Azomethine Ylide Chemistry.

Here, we report accessing small 3-fluoropyrrolidines and 3,3-difluoropyrrolidines through a 1,3-dipolar cycloaddition with a simple azomethine ylide and a variety of vinyl fluorides and vinyl difluorides. We demonstrate that vinyl fluorides within α,ß-unsaturated, styrenyl and even enol ether systems can participate in the cycloaddition reaction. The vinyl fluorides are relatively easy to synthesize through a variety of methods, making the 3-fluoropyrrolidines very accessible.

SAM-Competitive PRMT5 Inhibitor PF-06939999 Demonstrates Antitumor Activity in Splicing Dysregulated NSCLC with Decreased Liability of Drug Resistance.

Protein arginine methyltransferase 5 (PRMT5) overexpression in hematologic and solid tumors methylates arginine residues on cellular proteins involved in important cancer functions including cell-cycle regulation, mRNA splicing, cell differentiation, cell signaling, and apoptosis. PRMT5 methyltransferase function has been linked with high rates of tumor cell proliferation and decreased overall survival, and PRMT5 inhibitors are currently being explored as an approach for targeting cancer-specific dependencies due to PRMT5 catalytic function. Here, we describe the discovery of potent and selective S-adenosylmethionine (SAM) competitive PRMT5 inhibitors, with in vitro and in vivo characterization of clinical candidate PF-06939999. Acquired resistance mechanisms were explored through the development of drug resistant cell lines. Our data highlight compound-specific resistance mutations in the PRMT5 enzyme that demonstrate structural constraints in the cofactor binding site that prevent emergence of complete resistance to SAM site inhibitors. PRMT5 inhibition by PF-06939999 treatment reduced proliferation of non-small cell lung cancer (NSCLC) cells, with dose-dependent decreases in symmetric dimethyl arginine (SDMA) levels and changes in alternative splicing of numerous pre-mRNAs. Drug sensitivity to PF-06939999 in NSCLC cells associates with cancer pathways including MYC, cell cycle and spliceosome, and with mutations in splicing factors such as RBM10. Translation of efficacy in mouse tumor xenograft models with splicing mutations provides rationale for therapeutic use of PF-06939999 in the treatment of splicing dysregulated NSCLC.

Identification of novel pyrrolopyrazoles as protein kinase C ß II inhibitors.

A novel series of pyrrolopyrazole-based protein kinase C ß II inhibitors has been identified from high-throughput screening. Herein, we report our initial structure-activity relationship studies with a focus on optimizing compound ligand efficiency and physicochemical properties, which has led to potent inhibitors with good cell permeability.

Development of a Late-Stage Diversification Strategy for the 4- and 5-Positions of 4,5,6-Trisubstituted Indazoles.

Indazoles represent a privileged motif in drug discovery. However, the formation of highly substituted indazoles can require the execution of lengthy synthetic routes with minimal opportunities to introduce diversity. In this report, we disclose the development of a late-stage diversification strategy for the 4- and 5-positions of 4,5,6-trisubstituted indazoles. A regioselective C-H functionalization and subsequent nucleophilic aromatic substitution provide two sequential points of diversification. The synthetic sequence delivers rapid access to an array of 4,5,6-trisubstituted indazoles in only four steps from readily available starting materials.

Rhodium(III)-Catalyzed C-H Activation: Ligand-Controlled Regioselective Synthesis of 4-Methyl-Substituted Dihydroisoquinolones.

Rh-catalyzed C-H functionalization of O-pivaloyl benzhydroxamic acids with propene gas provides access to 4-methyl-substituted dihydroisoquinolones. Good to excellent levels of regioselectivity are achieved using [CptRhCl2]2 as a precatalyst under optimized conditions. Thorough examination of aryl/heteroaryl O-pivaloyl hydroxamic acid substrates, ligand effects on C-H site selectivity, alkene scope, and demonstration of scale are discussed within.

Discovery of Potent, Selective, and Peripherally Restricted Pan-Trk Kinase Inhibitors for the Treatment of Pain.

Hormones of the neurotrophin family, nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), neurotrophin 3 (NT3), and neurotrophin 4 (NT4), are known to activate the family of Tropomyosin receptor kinases (TrkA, TrkB, and TrkC). Moreover, inhibition of the TrkA kinase pathway in pain has been clinically validated by the NGF antibody tanezumab, leading to significant interest in the development of small molecule inhibitors of TrkA. Furthermore, Trk inhibitors having an acceptable safety profile will require minimal brain availability. Herein, we discuss the discovery of two potent, selective, peripherally restricted, efficacious, and well-tolerated series of pan-Trk inhibitors which successfully delivered three candidate quality compounds 10b, 13b, and 19. All three compounds are predicted to possess low metabolic clearance in human that does not proceed via aldehyde oxidase-catalyzed reactions, thus addressing the potential clearance prediction liability associated with our current pan-Trk development candidate PF-06273340.

Design and Synthesis of Pyridone-Containing 3,4-Dihydroisoquinoline-1(2H)-ones as a Novel Class of Enhancer of Zeste Homolog 2 (EZH2) Inhibitors.

A new enhancer of zeste homolog 2 (EZH2) inhibitor series comprising a substituted phenyl ring joined to a dimethylpyridone moiety via an amide linkage has been designed. A preferential amide torsion that improved the binding properties of the compounds was identified for this series via computational analysis. Cyclization of the amide linker resulted in a six-membered lactam analogue, compound 18. This transformation significantly improved the ligand efficiency/potency of the cyclized compound relative to its acyclic analogue. Additional optimization of the lactam-containing EZH2 inhibitors focused on lipophilic efficiency (LipE) improvement, which provided compound 31. Compound 31 displayed improved LipE and on-target potency in both biochemical and cellular readouts relative to compound 18. Inhibitor 31 also displayed robust in vivo antitumor growth activity and dose-dependent de-repression of EZH2 target genes.

Studies on the regioselective nucleophilic aromatic substitution (S(N)Ar) reaction of 2-substituted 3,5-dichloropyrazines.

Differences in regioselectivity were observed during the S(N)Ar reaction of amines with unsymmetrical 3,5-dichloropyrazines. This study revealed that when the 2-position of the pyrazine was occupied with an electron-withdrawing group (EWG), nucleophilic attack occurred preferentially at the 5-position. When the 2-position was substituted with an electron-donating group (EDG), nucleophilic attack occurred preferentially at the 3-position. These results are reported along with a computational rationale for the experimental observations based on the Fukui index at the reacting centers.

Discovery of a novel class of targeted kinase inhibitors that blocks protein kinase C signaling and ameliorates retinal vascular leakage in a diabetic rat model.

Protein kinase C (PKC) family members such as PKCbetaII may become activated in the hyperglycemic state associated with diabetes. Preclinical and clinical data implicate aberrant PKC activity in the development of diabetic microvasculature abnormalities. Based on this potential etiological role for PKC in diabetic complications, several therapeutic PKC inhibitors have been investigated in clinical trials for the treatment of diabetic patients. In this report, we present the discovery and preclinical evaluation of a novel class of 3-amino-pyrrolo[3,4-c]pyrazole derivatives as inhibitors of PKC that are structurally distinct from the prototypical indolocarbazole and bisindolylmaleimide PKC inhibitors. From this pyrrolo-pyrazole series, several compounds were identified from biochemical assays as potent, ATP-competitive inhibitors of PKC activity with high specificity for PKC over other protein kinases. These compounds were also found to block PKC signaling activity in multiple cellular functional assays. PF-04577806, a representative from this series, inhibited PKC activity in retinal lysates from diabetic rats stimulated with phorbol myristate acetate. When orally administered, PF-04577806 showed good exposure in the retina of diabetic Long-Evans rats and ameliorated retinal vascular leakage in a streptozotocin-induced diabetic rat model. These novel PKC inhibitors represent a promising new class of targeted protein kinase inhibitors with potential as therapeutic agents for the treatment of patients with diabetic microvascular complications.