Development of High-Throughput Experimentation Approaches for Rapid Radiochemical Exploration

Positron emission tomography is a widely used imaging platform for studying physiological processes. Despite the proliferation of modern synthetic methodologies for radiolabeling, the optimization of these reactions still primarily relies on inefficient one-factor-at-a-time approaches. High-throughput experimentation (HTE) has proven to be a powerful approach for optimizing reactions in many areas of chemical synthesis. However, to date, HTE has rarely been applied to radiochemistry. This is largely because of the short lifetime of common radioisotopes, which presents major challenges for efficient parallel reaction setup and analysis using standard equipment and workflows. Herein, we demonstrate an effective HTE workflow and apply it to the optimization of copper-mediated radiofluorination of pharmaceutically relevant boronate ester substrates. The workflow utilizes commercial equipment and allows for rapid analysis of reactions for optimizing reactions, exploring chemical space using pharmaceutically relevant aryl boronates for radiofluorinations, and constructing large radiochemistry data sets.

Profiling and Application of Photoredox C(sp3)-C(sp2) Cross-Coupling in Medicinal Chemistry

Recent visible-light photoredox catalyzed C(sp³)-C(sp²) cross-coupling provides a novel transformation to potentially enable the synthesis of medicinal chemistry targets. Here, we report a profiling study of photocatalytic C(sp³)-C(sp²) cross-coupling, both decarboxylative coupling and cross-electrophile coupling, with 18 pharmaceutically relevant aryl halides by using either Kessil lamp or our newly developed integrated photoreactor. Integrated photoreactor accelerates reaction rate and improves reaction success rate. Cross-electrophile coupling gives higher success rate with broad substrate scope on alkyl halides than that of the decarboxylative coupling. In addition, a successful application example on a discovery program demonstrates the efficient synthesis of medicinal chemistry targets via photocatalytic C(sp³)-C(sp²) cross-coupling by using our integrated photoreactor.

An In-House Built Semiautomated Countercurrent Chromatography Workstation

An elution—extrusion countercurrent chromatography workstation was designed and built in-house for fractionating crude natural product extracts. The engineering efforts of this project included both custom hardware and software integration. The resulting workstation operates four individual chromatography coils for natural product extract separation and purification. The workstation offers the ability to collect fractions into 16 × 100 mm borosilicate glass test tubes or allows for stream splitting of the coil effluent so that the fractions can be collected into both 16 × 100 mm borosilicate test tubes and a 96-well microplate. Solvent pumping for each of the chromatography columns is achieved through the use of syringe pumps. The workstation is controlled though a custom control software application, C_Cubed, written in Visual Basic 6.0 (VB6). Software architecture consists of three levels. At the lowest level, there are ActiveX dll device drivers that interface with the physical hardware. The middle layer is a custom scheduler allowing for multitasking of instrument movements. The upper level is composed of a Wizard-style user interface that mimics the scientific workflow. Finally, by using a software timer the software application was written to operate on a single thread, but exhibit multithreaded behavior.