Synthesis of an electronically-tuned minimally interfering alkynyl photo-affinity label to measure small molecule–protein interactions

Chia-Fu Chang,Adelphe Mfuh,Jinxu Gao,Hung-Yi Wu,Christina M Woo

doi:10.1016/j.tet.2018.03.024

Abstract

We report the synthesis of an electronically-tuned minimally interfering photo-affinity label (MI-PAL), a compact five-carbon tag functionalized with an alkyl diazirine and alkyne handle. MI-PAL is compatible with protein photo-conjugation, click chemistry and mass spectrometry and readily installed to complex molecules for biological target identification.

Highlights

In cellulo target identification of non-covalent ligands has been accelerated by the development of small multifunctional chemical tags embedded to the ligand
We hypothesized that strategic placement of fluorine adjacent to the alkyne and diazirine functional groups would improve the essential properties required for the chemical tag and provide synthetic access to a minimally-interfering photo-affinity label (MI-Photo-affinity labels (PALs), 3)
Elaboration of the ketone 6 to the diaziridine 8 was enabled by the difluoropropyne protected with triisopropylsilane (TIPS) to prevent undesired nucleophilic or deprotonation pathways promoted by basic ammonia

Summary

Introduction

In cellulo target identification of non-covalent ligands has been accelerated by the development of small multifunctional chemical tags embedded to the ligand. Of the available PALs, the diazirine has recently been applied in numerous target identification studies due to its small size.[6,7,8] Integration of the diazirine with an alkyne reporter handle have yielded chemical tags like the aryl diazirine 1,9 10.1 Å in length, or the “minimalist” tag (2),10 9.4 Å in length (Figure 1). The minimalist tag (2) has seen application in drug ontarget[11] and off-target identification,[11, 12] fragment based screening,[13] and binding site mapping.[13], We hypothesized that synthesis of an electronically-tuned five carbon tag, such as 3, would afford a smaller tag scaffold (6.9 Å)[15] with universally improved photo-conjugation and CuAAC properties (Figure 1).

Results

Conclusion