Aromatic sulfonyl fluorides covalently kinetically stabilize transthyretin to prevent amyloidogenesis while affording a fluorescent conjugate.

Molecules that bind selectively to a given protein and then undergo a rapid chemoselective reaction to form a covalent conjugate have utility in drug development. Herein a library of 1,3,4-oxadiazoles substituted at the 2 position with an aryl sulfonyl fluoride and at the 5 position with a substituted aryl known to have high affinity for the inner thyroxine binding subsite of transthyretin (TTR) was conceived of by structure-based design principles and was chemically synthesized. When bound in the thyroxine binding site, most of the aryl sulfonyl fluorides react rapidly and chemoselectively with the pKa-perturbed K15 residue, kinetically stabilizing TTR and thus preventing amyloid fibril formation, known to cause polyneuropathy. Conjugation t50s range from 1 to 4 min, ~1400 times faster than the hydrolysis reaction outside the thyroxine binding site. X-ray crystallography confirms the anticipated binding orientation and sheds light on the sulfonyl fluoride activation leading to the sulfonamide linkage to TTR. A few of the aryl sulfonyl fluorides efficiently form conjugates with TTR in plasma. Eleven of the TTR covalent kinetic stabilizers synthesized exhibit fluorescence upon conjugation and therefore could have imaging applications as a consequence of the environment sensitive fluorescence of the chromophore.

Antiviral stilbene 1,2-diamines prevent initiation of hepatitis C virus RNA replication at the outset of infection.

The recent development of a cell culture model of hepatitis C virus (HCV) infection based on the JFH-1 molecular clone has enabled discovery of new antiviral agents. Using a cell-based colorimetric screening assay to interrogate a 1,200-compound chemical library for anti-HCV activity, we identified a family of 1,2-diamines derived from trans-stilbene oxide that prevent HCV infection at nontoxic, low micromolar concentrations in cell culture. Structure-activity relationship analysis of ~ 300 derivatives synthesized using click chemistry yielded compounds with greatly enhanced low nanomolar potency and a > 1,000:1 therapeutic ratio. Using surrogate models of HCV infection, we showed that the compounds selectively block the initiation of replication of incoming HCV RNA but have no impact on viral entry, primary translation, or ongoing HCV RNA replication, nor do they suppress persistent HCV infection. Selection of an escape variant revealed that NS5A is directly or indirectly targeted by this compound. In summary, we have identified a family of HCV inhibitors that target a critical step in the establishment of HCV infection in which NS5A translated de novo from an incoming genomic HCV RNA template is required to initiate the replication of this important human pathogen.

Synthesis of 7-aza-5-deazapurine analogues via copper(I)-catalyzed hydroamination of alkynes and 1-iodoalkynes.

A new method for the synthesis of dihydroimidazo[1,2-a][1,3,5]triazin-4(6H)-ones via copper(I)-catalyzed hydroamination was developed. In addition, for the first time, iodoalkynes were shown to participate in the copper(I)-catalyzed intramolecular hydroamination reaction with exclusive formation of E-isomers.

Highly regioselective transformation of alkenyl bromides into alpha-bromoaziridines and alpha-bromohydrazones.

[reaction: see text] The synthetic utility of alpha-halohydrazones is an underexplored area due to the lack of chemo- and regioselective routes towards these molecules. Herein, we describe a general method for alpha-bromohydrazone synthesis via the rearrangement of alpha-bromoaziridines, which can be readily prepared for the first time from the corresponding alkenyl bromides. The rearrangement of alpha-bromoaziridines into alpha-bromohydrazones proceeds with high yields and with high selectivities.

p-Tolylsulfinyl amides: reagents for facile electrophilic functionalization of olefins.

A variety of olefins were found to react with sulfinyl amides in the presence of POCl(3) to give beta-chlorosulfides and beta-hydroxysulfides in good yields. In the absence of nucleophiles, p-tolylsulfinyl amides were found to react with olefins with the formation of allylsulfoxides.