A Linker for the Solid-Phase Synthesis of Hydroxamic Acids and Identification of HDAC6 Inhibitors

Sulfur(VI) Fluoride Exchange Chemistry in Solid-Phase Synthesis of Compound Arrays: Discovery of Histone Deacetylase Inhibitors

Multistep synthesis performed on solid support is a powerful means to generate small-molecule libraries for the discovery of chemical probes to dissect biological mechanisms as well as for drug discovery. Therefore, expansion of the collection of robust chemical transformations amenable to solid-phase synthesis is desirable for achieving chemically diverse libraries for biological testing. Here, we show that sulfur(VI) fluoride exchange (SuFEx) chemistry, exemplified by pairing phenols with aryl fluorosulfates, can be used for the solid-phase synthesis of biologically active compounds. As a case study, we designed and synthesized a library of 84 hydroxamic acid-containing small molecules, providing a rich source of inhibitors with diverse selectivity profiles across the human histone deacetylase enzyme family. Among other discoveries, we identified a scaffold that furnished inhibitors of HDAC11 with exquisite selectivity in vitro and a selective inhibitor of HDAC6 that was shown to affect the acetylation of α-tubulin over histone sites H3K18, H3K27, as well as SMC3 in cultured cells. Our results encourage the further use of SuFEx chemistry for the synthesis of diverse small-molecule libraries and provide insight for future design of selective HDAC inhibitors.

Solid-Phase Synthesis of PROTACs and SNIPERs on Backbone Amide Linked (BAL) Resin

Developing straightforward but flexible approaches to PROTAC synthesis that can incorporate the structural elements of emerging designs can improve the quality and efficiency of PROTAC development. Solid-phase approaches could offer many advantages over conventional PROTAC synthesis if diverse chemistries and topographies can be incorporated. We have exploited the backbone-amide-linked (BAL) resin to employ an array of solid-phase organic reactions, providing access to VHL- and IAP-targeting degraders using the BRD4-targeting JQ1 conjugates as examples.

Convergent Total Synthesis of Exochelin 772SM

A convergent total synthesis of the natural mycobacterial iron chelator desferri-exochelin 772SM (D-EXO) is described. The synthetic procedure proceeds in 11 steps in the longest linear sequence, with an overall yield of 8.6%. The described procedure uses cheap starting materials and requires a limited number of chromatographic purifications. The concise strategy divides the exochelin into five key building blocks, allowing easy alternation of each single building block. Herein, the presented synthetic strategy is well suited to facilitate the synthesis of analogues and medicinal chemistry development efforts in a time- and resource-efficient manner.