Jesus R. Medina

Discovery of GSK2656157: An Optimized PERK Inhibitor Selected for Preclinical Development.

We recently reported the discovery of GSK2606414 (1), a selective first in class inhibitor of protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), which inhibited PERK activation in cells and demonstrated tumor growth inhibition in a human tumor xenograft in mice. In continuation of our drug discovery program, we applied a strategy to decrease inhibitor lipophilicity as a means to improve physical properties and pharmacokinetics. This report describes our medicinal chemistry optimization culminating in the discovery of the PERK inhibitor GSK2656157 (6), which was selected for advancement to preclinical development.

9-Borabicyclo[3.3.2]decanes and the asymmetric hydroboration of 1,1-disubstituted alkenes.

The syntheses of the optically pure asymmetric hydroborating agents 1 (a, R = Ph; b, R = TMS) in both enantiomeric forms are reported. These reagents are effective for the hydroboration of cis-, trans- and trisubstituted alkenes. More significantly, they exhibit unprecedented levels of selectivity in the asymmetric hydroboration of 1,1-disubstituted alkenes (28-92% ee), a previously unanswered challenge in the nearly 50 year history of this reagent-controlled process. For example, the hydroboration of alpha-methylstyrene with 1a produces the corresponding alcohol 6f in 78% ee (cf., Ipc2BH, 5% ee). Suzuki coupling of the intermediate adducts 5 produces the nonracemic products 7 very effectively (50-84%) without loss of optical purity.

Structure-Based Design of Potent and Selective 3-Phosphoinositide-Dependent Kinase-1 (PDK1) Inhibitors.

Phosphoinositide-dependent protein kinase-1(PDK1) is a master regulator of the AGC family of kinases and an integral component of the PI3K/AKT/mTOR pathway. As this pathway is among the most commonly deregulated across all cancers, a selective inhibitor of PDK1 might have utility as an anticancer agent. Herein we describe our lead optimization of compound 1 toward highly potent and selective PDK1 inhibitors via a structure-based design strategy. The most potent and selective inhibitors demonstrated submicromolar activity as measured by inhibition of phosphorylation of PDK1 substrates as well as antiproliferative activity against a subset of AML cell lines. In addition, reduction of phosphorylation of PDK1 substrates was demonstrated in vivo in mice bearing OCl-AML2 xenografts. These observations demonstrate the utility of these molecules as tools to further delineate the biology of PDK1 and the potential pharmacological uses of a PDK1 inhibitor.

Selective 3-phosphoinositide-dependent kinase 1 (PDK1) inhibitors: dissecting the function and pharmacology of PDK1.

3-Phosphoinositide-dependent protein kinase 1 (PDK1) is a protein target that has generated considerable interest in both academia and the pharmaceutical industry. PDK1 is responsible for regulating the activity of related kinases in the AGC kinase family, including AKT, by phosphorylating a specific threonine or serine residue within the activation loop which is critical for kinase activation. Many of the kinases activated by PDK1 regulate cellular process such as cell survival, differentiation, growth, and protein expression. Although significant work has been done to understand the role of PDK1 function in cells, recently discovered potent and selective small molecule PDK1 inhibitors are providing a unique opportunity to further dissect PDK1 function and predict the pharmacological consequences of PDK1 inhibition. This Miniperspective reviews the discovery of these selective PDK1 inhibitors and highlights their value in cellular studies, the understanding of PDK1 biology, and the impact on the therapeutic potential of PDK1 inhibition in cancer.

Aminoindazole PDK1 Inhibitors: A Case Study in Fragment-Based Drug Discovery.

Fragment screening of phosphoinositide-dependent kinase-1 (PDK1) in a biochemical kinase assay afforded hits that were characterized and prioritized based on ligand efficiency and binding interactions with PDK1 as determined by NMR. Subsequent crystallography and follow-up screening led to the discovery of aminoindazole 19, a potent leadlike PDK1 inhibitor with high ligand efficiency. Well-defined structure-activity relationships and protein crystallography provide a basis for further elaboration and optimization of 19 as a PDK1 inhibitor.

NOVEL HYDROBORATING AGENTS FROM SILYLAMINE-BORANES

Abstract Exhibiting a broad spectrum of hydroboration reactivities, seven (7) new silylamine-borane complexes ( 1 ) were efficiently prepared from diborane and the corresponding silylated amines ( 2 ). Most are crystalline solids which are air-stable, concentrated borane sources. All provide convenient alternatives to other hydroborating agents, 2 undergoing complete hydrolysis to volatile and/or water soluble by-products upon aqueous work-up, thereby greatly facilitating the isolation of the borane-derived reaction products.

Mono- and dialkylborane reagents from silylamine-boranes

Abstract New procedures for the simple, efficient preparation of thexylborane (ThxBH 2 ), disiamylborane (Siam 2 BH), 9-borabicyclo[3.3.1]nonane (9-BBN-H) and diisopinocampheylborane (ipc 2 BH) are described employing silylamine-boranes ( 1 ). By selecting a less reactive reagent, dicyclohexylborane (Chx 2 BH), was prepared directly from hydroboration in crystalline form for the first time. These new methods demonstrate that the silylamine by-products ( 2 ) neither interfere with subsequent reactions or purification of the borane reagents, nor pose any difficulties in their separation from the borane-derived products.

Benzyl 2-cyano-3,3-dimethyl-1-pyrrolidinecarboxylate, a versatile intermediate for the synthesis of 3,3-dimethylproline derivatives.

The synthesis of racemic nitrile (+/-)-9 was accomplished in four steps and 58% overall yield from the known pyrrolidinone 5. Nitrile (+/-)-9 was resolved via preparative chiral HPLC to afford optically pure nitriles (+)-9 and (-)-9, from which 3,3-dimethylprolines (+)-1 and (-)-1 and 3,3-dimethylprolinamides (+)-2 and (-)-2 could be accessed in nearly quantitative yield, without loss of optical purity. The absolute configurations of the resolved prolines and prolinamides were determined by correlation with an intermediate of known absolute stereochemistry.