Achim Schlapbach

A general palladium-catalysed synthesis of aromatic and heteroaromatic thioethers

Abstract Thioethers can be efficiently prepared via palladium-catalysed cross-coupling of arene- or heteroarene thiols with arene- or heteroarene iodides. A simple, cheap and robust catalytic system is described that couples a broad range of electron-deficient as well as electron-rich substrates in high yield.

Identification of Human Kinases Involved in Hepatitis C Virus Replication by Small Interference RNA Library Screening

The propagation of the hepatitis C virus (HCV) is a complex process that requires both host and viral proteins. To facilitate identification of host cell factors that are required for HCV replication, we screened a panel of small interference RNAs that preferentially target human protein kinases using an HCV replicon expressing the firefly luciferase gene as a genetic reporter. Small interference RNAs specific for three human kinases, Csk, Jak1, and Vrk1, were identified that reproducibly reduce viral RNA and viral protein levels in HCV replicon-bearing cells. Treatment of replicon cells with a small molecule inhibitor of Csk also resulted in a significant reduction in HCV RNA and proteins, further supporting a role for Csk in HCV replication. The effects of siRNAs targeting eight kinases known to be negatively regulated by Csk were then examined; knock down of one of these kinases, Fyn, resulted in up-regulation of the HCV replicon, suggesting that Csk mediates its effect on HCV replication through Fyn. This conclusion was further corroborated by demonstration that replicon cells treated with Csk inhibitor contained lower levels of the phosphorylated form of Fyn than control cells.

Stereocontrol in allylboration reactions

Abstraat: Crotyl-boronates add to aldehydes with high simple diastereoselection, such that E-crotyl-boronates give d-homoallyl alcohols, and Z-crotyl-boronates their =-counterparts. This reaction has been extended to stereoselective ring closure reactions by intramolecular allylboration. Moreover, by using suitably substituted crotyl boronates homoallyl alcohols having quarternary stereogenic carbon centers have been obtained with good diastereoselection. The development of chiral crotyl boronate reagents, having an additional stereogenic center a to the boron atom, allowed reactions with aldehydes to be accomplished with full transfer of chirality; i.e. control of the absolute configuration of the products.

Pyrrolo-pyrimidones: a novel class of MK2 inhibitors with potent cellular activity.

Pyrrolo-pyrimidones of the general structure 1 were synthesized and evaluated for their potential as MK2 inhibitors. Potent derivatives were discovered which inhibit MK2 in the nanomolar range and show potent inhibition of cytokine release from LPS-stimulated monocytes. These derivatives were shown to inhibit phosphorylation of hsp27, a downstream target of MK2 and are modestly selective in a panel of 28 kinases.

Novel 3-aminopyrazole inhibitors of MK-2 discovered by scaffold hopping strategy.

New, selective 3-aminopyrazole based MK2-inhibitors were discovered by scaffold hopping strategy. The new derivatives proved to inhibit intracellular phosphorylation of hsp27 as well as LPS-induced TNFalpha release in cells. In addition, selected derivative 14e also inhibited LPS-induced TNFalpha release in vivo.

Low-molecular-weight MK2 inhibitors: a tough nut to crack!

The p38 pathway has been at the center of interest for anti-inflammatory drug discovery for many years as it is crucial for the biosynthesis of TNF-α, IL-1β and other mediators. Most of the anti-inflammatory effects of p38 inhibition are mediated through MAPK-activated protein kinase-2 (MK2), a direct downstream target of p38, which makes MK2 a very interesting drug target. Within the last 5 years, several classes of low-molecular-weight MK2 inhibitors were disclosed in the patent and primary literature. Advanced compounds could be optimized to nanomolar potencies and inhibit TNF-α release, as well as the phosphorylation of the MK2 substrate heat-shock protein 27 in cellular assays. This article will review the recent progress in this field and will highlight and discuss the most promising compound series disclosed so far.

Synthesis of the trioxadecalin-part of mycalamide B

Abstract A stereoselective synthesis of the trioxadecalin part of mycalamide B has been realized starting from 2,4,3,5-dimethylene-L-xylose. The C-10-aminal stereocenter is generated by a Curtius degradation.

In vivo and in vitro SAR of tetracyclic MAPKAP-K2 (MK2) inhibitors. Part II.

Spirocyclopropane- and spiroazetidine-substituted tetracycles 13D-E and 16A are described as orally active MK2 inhibitors. The spiroazetidine derivatives are potent MK2 inhibitors with IC(50)<3 nM and inhibit the release of TNFalpha (IC(50)<0.3 microM) from hPBMCs and hsp27 phosphorylation in anisomycin stimulated THP-1 cells. The spirocyclopropane analogues are less potent against MK2 (IC(50)=0.05-0.23 microM), less potent in cells (IC(50)<1.1 microM), but show good oral absorption. Compound 13E (100mg/kg po; bid) showed oral activity in rAIA and mCIA, with significant reduction of swelling and histological score.

Allylboration-reactions, the key to a short synthesis of benzoyl-pedamide☆

Abstract Benzoyl-pedamide (2 a key building block for the synthesis of pederin, has been synthesized in 13 steps from malic acid. The new stereogenic centers have been generated under reagent control of diastereoselectivity with selectivities of 87 and 80% using the newly developed chiral-α substituted allylboronate 16 as well as 21 as reagents.

Discovery of a novel class of highly potent inhibitors of the p53-MDM2 interaction by structure-based design starting from a conformational argument.

The p53-MDM2 interaction is an anticancer drug target under investigation in the clinic. Our compound NVP-CGM097 is one of the small molecule inhibitors of this protein-protein interaction currently evaluated in cancer patients. As part of our effort to identify new classes of p53-MDM2 inhibitors that could lead to additional clinical candidates, we report here the design of highly potent inhibitors having a pyrazolopyrrolidinone core structure. The conception of these new inhibitors originated in a consideration on the MDM2 bound conformation of the dihydroisoquinolinone class of inhibitors to which NVP-CGM097 belongs. This work forms the foundation of the discovery of HDM201, a second generation p53-MDM2 inhibitor that recently entered phase I clinical trial.