Recent reports indicate that some cancer types are especially sensitive to transcription inhibition, suggesting that targeting the transcriptional machinery provides new approaches to cancer treatment. Cyclin-dependent kinase (CDK)7 is necessary for transcription, and acts by phosphorylating the C-terminal domain (CTD) of RNA polymerase II (PolII) to enable transcription initiation. CDK7 additionally regulates the activities of a number of transcription factors, including estrogen receptor (ER)-α. Here we describe a new, orally bioavailable CDK7 inhibitor, ICEC0942. It selectively inhibits CDK7, with an IC of 40 nmol/L; IC values for CDK1, CDK2, CDK5, and CDK9 were 45-, 15-, 230-, and 30-fold higher. studies show that a wide range of cancer types are sensitive to CDK7 inhibition with GI values ranging between 0.2 and 0.3 μmol/L. In xenografts of both breast and colorectal cancers, the drug has substantial antitumor effects. In addition, combination therapy with tamoxifen showed complete growth arrest of ER-positive tumor xenografts. Our findings reveal that CDK7 inhibition provides a new approach, especially for ER-positive breast cancer and identify ICEC0942 as a prototype drug with potential utility as a single agent or in combination with hormone therapies for breast cancer. ICEC0942 may also be effective in other cancers that display characteristics of transcription factor addiction, such as acute leukaemia and small-cell lung cancer. .

Cyclin-dependent protein kinases (CDKs) are central to the appropriate regulation of cell proliferation, apoptosis, and gene expression. Abnormalities in CDK activity and regulation are common features of cancer, making CDK family members attractive targets for the development of anticancer drugs. Here, we report the identification of a pyrazolo[1,5-a]pyrimidine derived compound, 4k (BS-194), as a selective and potent CDK inhibitor, which inhibits CDK2, CDK1, CDK5, CDK7, and CDK9 (IC₅₀= 3, 30, 30, 250, and 90 nmol/L, respectively). Cell-based studies showed inhibition of the phosphorylation of CDK substrates, Rb and the RNA polymerase II C-terminal domain, down-regulation of cyclins A, E, and D1, and cell cycle block in the S and G₂/M phases. Consistent with these findings, 4k demonstrated potent antiproliferative activity in 60 cancer cell lines tested (mean GI₅₀= 280 nmol/L). Pharmacokinetic studies showed that 4k is orally bioavailable, with an elimination half-life of 178 min following oral dosing in mice. When administered at a concentration of 25 mg/kg orally, 4k inhibited human tumor xenografts and suppressed CDK substrate phosphorylation. These findings identify 4k as a novel, potent CDK selective inhibitor with potential for oral delivery in cancer patients.

Enantioenriched bicyclo[4.1.0]hept-2-enes were synthesized by Ir(I)-catalyzed carbocyclization of 1,6-enynes. No chiral ligands were used, CO and PPh(3) were the only ligands bound to iridium. Instead, the stereochemical information was localized on the counterion of the catalyst, generated in situ by reaction of Vaska's complex (trans-[IrCl(CO)(PPh(3))(2)]) with a chiral silver phosphate. Enantiomeric excesses up to 93% were obtained when this catalytic mixture was used. (31)P NMR and IR spectroscopy suggest that formation of the trans- [Ir(CO)(PPh(3))(2)](+) moiety occurs by chlorine abstraction. Moreover, density functional theory calculations support a 6-endo-dig cyclization promoted by this cationic moiety. The chiral phosphate anion (O-P*) controls the enantioselectivity through formation of a loose ion pair with the metal center and establishes a C-H···O-P* hydrogen bond with the substrate. This is a rare example of asymmetric counterion-directed transition-metal catalysis and represents the first application of such a strategy to a C-C bond-forming reaction.

Table of contents entryWe have solved crystal structures of CDK7--selective inhibitors bound to CDK2.We have used a combination of structural, biophysical and modelling approaches to model the binding of these inhibitors to CDK7, and have used this information to explain their selectivity. We identify specific CDK7 residues that contribute to these inhibitors' specificity. AbstractDeregulation of the cell cycle by mechanisms that lead to elevated activities of cyclin--dependent kinases (CDK) is a feature of many human diseases, in particular cancer. We have identified small molecule inhibitors that selectively inhibit CDK7, the kinase that phosphorylates cell cycle CDKs to promote their activities. To investigate the selectivity of these inhibitors we have used a combination of structural, biophysical and modelling approaches. We have determined crystal structures of the CDK7 selective compounds ICEC0942 and ICEC0943 bound to CDK2, and used these to build models of inhibitor binding to CDK7. Molecular dynamics simulations of inhibitors bound to CDK2 and CDK7 have generated possible models of inhibitor binding. In order to experimentally 3 validate these models, we measured isothermal titration calorimetry (ITC) binding data for recombinant wild type and binding site mutants of CDK7 and CDK2. We have identified specific residues of CDK7, notably Asp155, that are involved in determining inhibitor selectivity. Our molecular dynamics simulations also show that the flexibility of the G--rich and activation loops of CDK7 is likely an important determinant of inhibitor specificity similar to CDK2.4

Herein we describe the formation and use of silyl cobalt(III) dihydride complexes as powerful catalysts for the hydrosilylation of a variety of imines starting from a low-valent welldefined cobalt(I) complex. The reaction is efficient at low catalyst loadings with a diverse range of imines bearing various protecting groups, as well as aliphatic ketimines and quinoline. Kinetics, DFT calculations, NMR spectroscopic studies, deuteration experiments and X-ray diffraction analysis allowed us to propose a catalytic cycle based on silyl dihydrocobalt(III) complexes performing a hydrocobaltation.

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Sigmatropic rearrangements of 3-(N-tosylamino)allylic alcohol derivatives, a particular subclass of functionalized enamides, have been investigated. Whereas the presence of the nitrogen atom alters the stereochemical outcome of Ireland-Claisen rearrangements of glycolates derived from such substrates, [2,3]-Wittig rearrangements of α-allyloxy acetamides or propargylic ethers derivatives provide access to a wide variety of functionalized 1,2-amino alcohols usually with high levels of stereocontrol, as well as to heterocyclic compounds. The stereoselectivity issues of these rearrangements (1,2-diastereoselectivity, auxiliary-induced diastereoselection, chirality transfer, and double stereodifferentiation) were thoroughly investigated.

International audienceThe first polymerization exploiting the carbenic reactivity of homogeneous gold catalysis has been devised. In the presence of a gold catalyst, monomers incorporating both a propargylic ester and an alkene moiety polymerized through a metallocarbene generation/cyclopropanation sequence to afford the corresponding macromolecules. This approach constitutes an unprecedented example of cyclopropanation-based polymerization and allows access to original macro-molecule skeletons