Development of selective inhibitors of phosphatidylinositol 3-kinase C2α.

Phosphatidylinositol 3-kinase type 2α (PI3KC2α) and related class II PI3K isoforms are of increasing biomedical interest because of their crucial roles in endocytic membrane dynamics, cell division and signaling, angiogenesis, and platelet morphology and function. Herein we report the development and characterization of PhosphatidylInositol Three-kinase Class twO INhibitors (PITCOINs), potent and highly selective small-molecule inhibitors of PI3KC2α catalytic activity. PITCOIN compounds exhibit strong selectivity toward PI3KC2α due to their unique mode of interaction with the ATP-binding site of the enzyme. We demonstrate that acute inhibition of PI3KC2α-mediated synthesis of phosphatidylinositol 3-phosphates by PITCOINs impairs endocytic membrane dynamics and membrane remodeling during platelet-dependent thrombus formation. PITCOINs are potent and selective cell-permeable inhibitors of PI3KC2α function with potential biomedical applications ranging from thrombosis to diabetes and cancer.

Conformationally Controlled Linear and Helical Hydrocarbons Bearing Extended Side Chains.

Conformationally controlled flexible molecules are ideal for applications in medicine and materials, where shape matters but an ability to adapt to multiple and changing environments is often required. The conformation of flexible hydrocarbon chains bearing contiguous methyl substituents is controlled through the avoidance of syn-pentane interactions: alternating syn-anti isomers adopt a linear conformation while all-syn isomers adopt a helical conformation. From a simple diamond lattice analysis, larger substituents, which would be required for most potential applications, result in significant and unavoidable syn-pentane interactions, suggesting substantially reduced conformational control. Through a combination of computation, synthesis, and NMR analysis, we have identified a selection of substitution patterns that allow large groups to be incorporated on conformationally controlled linear and helical hydrocarbon chains. Surprisingly, when the methyl substituents of alternating syn-anti hydrocarbons are replaced with acetoxyethyl groups, the main chain of almost 95% of the population of molecules adopt a linear conformation. Here, the side chains adopt nonideal eclipsed conformations with the main chain, thus minimizing syn-pentane interactions. In the case of all-syn hydrocarbons, concurrent removal of some methyl groups on the main chain adjacent to the large substituents is required to maintain a high population of molecules adopting a helical conformation. This information can now be used to design flexible hydrocarbon chains displaying functional groups in a defined relative orientation for multivalent binding or cooperative reactivity, for example, in targeting the interfaces defined by disease-relevant protein-protein interactions.

Visible Light-Induced Sulfonylation/Arylation of Styrenes in a Double Radical Three-Component Photoredox Reaction.

Simultaneous sulfonylation/arylation of styrene derivatives is achieved in a photoredox-catalyzed three-component reaction using visible light. A broad variety of difunctionalized products is accessible in mostly excellent yields and high diastereoselectivity. The developed reaction is scalable and suitable for the modification of styrene-functionalized biomolecules. Mechanistic investigations suggest the transformation to be operating through a designed sequence of radical formation and radical combination.

α-Sulfinyl Benzoates as Precursors to Li and Mg Carbenoids for the Stereoselective Iterative Homologation of Boronic Esters.

The stereoselective reagent-controlled homologation of boronic esters is one of a small number of iteratable synthetic transformations that if automated could form the basis of a veritable molecule-making machine. Recently, α-stannyl triisopropylbenzoates and α-sulfinyl chlorides have emerged as useful building blocks for the iterative homologation of boronic esters. However, α-stannyl benzoates need to be prepared using stoichiometric amounts of the (+)- or (-)-enantiomer of the scarcely available and expensive diamine sparteine; also, these building blocks, together with the byproducts that are generated during homologation, are perceived as being toxic. On the other hand, α-sulfinyl chlorides are difficult to prepare with high levels of enantiopurity and are prone to undergo deleterious acid-base side-reactions under the reaction conditions for homologation, leading to low stereospecificity. Here, we show that the use of a hybrid of these two building blocks, namely, α-sulfinyl triisopropylbenzoates, largely overcomes the above drawbacks. Through either the sulfinylation of α-magnesiated benzoates with either enantiomer of Andersen's readily available menthol-derived sulfinate or the α-alkylation of enantiopure S-chiral α-sulfinyl benzoates, we have prepared a range of highly enantiopure mono- and disubstituted α-sulfinyl benzoates, some bearing sensitive functional groups. Barbier-type reaction conditions have been developed that allow these building blocks to be converted into lithium (t-BuLi) and magnesium (i-PrMgCl·LiCl) carbenoids in the presence of boronic esters, thus allowing efficient and highly stereospecific homologation. The use of magnesium carbenoids allows carbon chains to be grown with the incorporation of sensitive functional groups, such as alkyl/aryl halides, azides, and esters. The use of lithium carbenoids, which are less sensitive to steric hindrance, allows sterically encumbered carbon-carbon bonds to be forged. We have also shown that these building blocks can be used consecutively in three- and four-step iterative homologation processes, without intervening column chromatography, to give contiguously substituted carbon chains with very high levels of enantio- and diastereoselectivity.

3,4-Dihydro-2H-pyrrole-2-carbonitriles: Useful Intermediates in the Synthesis of Fused Pyrroles and 2,2'-Bipyrroles.

Various heterocyclic structures containing the pyrrole moiety have been synthesized from easily accessible 3,4-dihydro-2H-pyrrole-2-carbonitriles in one-pot procedures. 5,6,7,8-Tetrahydroindolizines, 2,3-dihydro-1H-pyrrolizines as well as 6,7,8,9-tetrahydro-5H-pyrrolo[1,2-a]azepines were obtained from these precursors in high yields in an alkylation/annulation sequence. The same conditions were applied in the synthesis of a 5,8-dihydroindolizine, which could easily be transformed to the corresponding indolizine by dehydrogenation. Furthermore, oxidative couplings of 3,4-dihydro-2H-pyrrole-2-carbonitriles with copper(II)-salts furnished 2,2'-bipyrroles as well as 5,5'-bis(5-cyano-1-pyrrolines), depending on the reaction conditions. Overall, these methods give high yielding access to a variety of pyrrole-containing heterocyles in two steps from commercially available starting materials.

Enantioselective Synthesis of α-Quaternary Amino Acids by Alkylation of Deprotonated α-Aminonitriles.

A series of α-quaternary arylglycines were prepared in high optical purity (up to 98% ee) by α-alkylation of deprotonated α-aminonitriles derived by the Strecker reaction from (4S,5S)-5-amino-2,2-dimethyl-4-phenyl-1,3-dioxane. The procedure includes only chromatographic purification of the final products and is devoid of chromatography or crystallization operations on intermediates to raise the optical purity.

One-pot synthesis of pyrrole-2-carboxylates and -carboxamides via an electrocyclization/oxidation sequence.

An electrocyclic ring closure is the key step of an efficient one-pot method for the synthesis of pyrrole-2-carboxylates and -carboxamides from chalcones and glycine esters or amides. The 3,4-dihydro-2H-pyrrole intermediates generated in situ are oxidized to the corresponding pyrroles by stoichiometric oxidants or by catalytic copper(II) and air in moderate to high yields. A wide range of functional groups are tolerated, and further combination with an in situ bromination gives access to polyfunctional pyrrole scaffolds.

Simple two-step synthesis of 2,4-disubstituted pyrroles and 3,5-disubstituted pyrrole-2-carbonitriles from enones.

The cyclocondensation of enones with aminoacetonitrile furnishes 3,4-dihydro-2H-pyrrole-2-carbonitriles which can be readily converted to 2,4-disubstituted pyrroles by microwave-induced dehydrocyanation. Alternatively, oxidation of the intermediates produces 3,5-disubstituted pyrrole-2-carbonitriles.

One-pot synthesis of polysubstituted indolizines by an addition/cycloaromatization sequence.

Indolizines carrying various substituents in positions 5-8 were obtained from readily available 2-(1H-pyrrol-1-yl)nitriles and α,ß-unsaturated ketones or aldehydes in a one-pot procedure. Michael addition of the deprotonated aminonitriles to the acceptors followed by acid-catalyzed electrophilic cyclization produces 5,6-dihydroindolizine-5-carbonitriles. From these stable intermediates, substituted indolizines were obtained via base-induced dehydrocyanation.

Structural Basis for Highly Selective Class II Alpha Phosphoinositide-3-Kinase Inhibition.

Class II phosphoinositide-3-kinases (PI3Ks) play central roles in cell signaling, division, migration, and survival. Despite evidence that all PI3K class II isoforms serve unique cellular functions, the lack of isoform-selective inhibitors severely hampers the systematic investigation of their potential relevance as pharmacological targets. Here, we report the structural evaluation and molecular determinants for selective PI3K-C2α inhibition by a structure-activity relationship study based on a pteridinone scaffold, leading to the discovery of selective PI3K-C2α inhibitors called PITCOINs. Cocrystal structures and docking experiments supported the rationalization of the structural determinants essential for inhibitor activity and high selectivity. Profiling of PITCOINs in a panel of more than 118 diverse kinases showed no off-target kinase inhibition. Notably, by addressing a selectivity pocket, PITCOIN4 showed nanomolar inhibition of PI3K-C2α and >100-fold selectivity in a general kinase panel. Our study paves the way for the development of novel therapies for diseases related to PI3K-C2α function.