Synthesis of a Novel Symmetrical Photoprotecting Group for the Efficient Capture and Release of Cysteine Sulfenic Acids on Oxidized Proteins from Streptavidin Beads

Candidate: Thershan Satkunarajah

Supervisors: Dr. Michael Olson and Dr. Russell Viirre

Abstract:
The Olson group has recently investigated reactive oxygen species (ROS) using a probe comprised of bicyclo[6.1.0]non-4-ynes. BCNs have been previously shown to provide fast reaction kinetics with cysteine sulfenic acids via a pericyclic reaction, while also enabling copper-free click chemistry, allowing for a biotin azide tag to be installed. However, due to the strong biotin-streptavidin interaction, these probes suffer from poor protein recovery and sub-optimal performance during mass-spectrometric analysis, respectively. Efforts towards incorporating the BCNs into a novel symmetrical photoprotecting group based on 1,4-naphthoquinone are proposed to improve upon these limitations and are presented in this thesis. Both endo- and exo- isomers of the BCNs have been synthesized using a 4-step protocol employing a copper (II) catalyst. The required diene for the Diels-Alder has been synthesized through a Suzuki-coupling approach using either the vinyl bromide or iodide. A family of derivatives based on the target molecule have been synthesized containing acetate, p-toluate, methyl carbonate, and triphenylsiloxy leaving groups. Photochemistry testing on the carbonate and p-toluate molecule suggests a more acidic leaving group should be incorporated into the naphthoquinone framework to have better photocleavage efficiency. In its stead, photocleavable biotin azide based on the 2-nitrobenzyl photoprotecting group has been synthesized and will be used alongside the previous probe to investigate if mass-spectrometric can be improved. Future work should focus on attaching the BCNs to the naphthoquinone core through a phosphate connection, and synthesizing a symmetrical bis(BCN)-bis(nitrobenzyl) tethered probe.