Deregulation of the PRC2 complex, comprised of the core subunits EZH2, SUZ12, and EED, drives aberrant hypermethylation of H3K27 and tumorigenicity of many cancers. Although inhibitors of EZH2 have shown promising clinical activity, preclinical data suggest that resistance can be acquired through secondary mutations in EZH2 that abrogate drug target engagement. To address these limitations, we have designed several hetero-bifunctional PROTACs (proteolysis-targeting chimera) to efficiently target EED for elimination. Our PROTACs bind to EED (pK D $ 9.0) and promote ternary complex formation with the E3 ubiquitin ligase. The PROTACs potently inhibit PRC2 enzyme activity (pIC 50 $ 8.1) and induce rapid degradation of not only EED but also EZH2 and SUZ12 within the PRC2 complex. Furthermore, the PROTACs selectively inhibit proliferation of PRC2-dependent cancer cells (half maximal growth inhibition [GI 50 ] = 49-58 nM). In summary, our data demonstrate a therapeutic modality to target PRC2-dependent cancer through a PROTACmediated degradation mechanism.

A practical approach for the stereoselective introduction of beta-arabinofuranosides has been developed on the basis of locking an arabinosyl donor in a conformation in which nucleophilic attack from the beta face is favored. The new glycosyl donor was designed by analyzing optimized geometries of low-energy conformers of the arabinofuranosyl oxacarbenium ion. The Newman projection of the E(3) conformer indicated that nucleophilic attack from the alpha face is disfavored because an eclipsed H-2 will be encountered. On the other hand, an approach from the beta face was expected to be more favorable, because it will experience only staggered substituents. The arabinofuranosyl oxacarbenium ion could be locked in the E(3) conformation by employing a 3,5-O-di-tert-butylsilane protecting group, which places C-5 and O-3 in a pseudoequatorial orientation, resulting in a perfect chair conformation of the protecting group. The new glycosyl donor gave excellent beta selectivities in a range of glycosylations with glycosyl acceptors having primary and secondary alcohols. The attractiveness of the new methodology was demonstrated by the chemical synthesis of a fragment of arabinogalactan, which is an important constituent of the primary plant cell wall.

TMSOTf-promoted glycosylations of 2-azido-2-deoxy-glucosyl trichloroacetimidates provide excellent alpha-anomeric selectivities when performed at a relatively high reaction temperature in the presence of PhSEt or thiophene. NMR and computation studies have shown that these glycosylations proceed through an equatorial anomeric sulfonium ion, which upon displacement by a sugar alcohol provides an axial glycoside. Computational studies have indicated that steric factors determine the selective formation of the beta-anomeric sulfonium ion.

Fragment-based drug discovery approaches allow for a greater coverage of chemical space and generally produce high efficiency ligands. As such, virtual and experimental fragment screening are increasingly being coupled in an effort to identify new leads for specific therapeutic targets. Fragment docking is employed to create target-focussed subset of compounds for testing along side generic fragment libraries. The utility of the program Glide with various scoring schemes for fragment docking is discussed. Fragment docking results for two test cases, prostaglandin D2 synthase and DNA ligase, are presented and compared to experimental screening data. Self-docking, cross-docking, and enrichment studies are performed. For the enrichment runs, experimental data exists indicating that the docking decoys in fact do not inhibit the corresponding enzyme being examined. Results indicate that even for difficult test cases fragment docking can yield enrichments significantly better than random.

Thymidylate kinase (TMK) is an essential enzyme in bacterial DNA synthesis. The deoxythymidine monophosphate (dTMP) substrate binding pocket was targeted in a rational-design, structure-supported effort, yielding a unique series of antibacterial agents showing a novel, induced-fit binding mode. Lead optimization, aided by X-ray crystallography, led to picomolar inhibitors of both Streptococcus pneumoniae and Staphylococcus aureus TMK. MICs < 1 μg/mL were achieved against methicillin-resistant S. aureus (MRSA), S. pneumoniae, and vancomycin-resistant Enterococcus (VRE). Log D adjustments yielded single diastereomers 14 (TK-666) and 46, showing a broad antibacterial spectrum against Gram-positive bacteria and excellent selectivity against the human thymidylate kinase ortholog.