New Fluorous Photoaffinity Labels (F-PAL) and Their Application in V-ATPase Inhibition Studies

(Trifluoromethyl)diazirines are well established photoaffinity labels (PAL) used in biochemical investigations to create covalent ligand-receptor bonds. Two new diazirinylbenzoic acids 8b,c with perfluorobutyl and perfluorooctyl chains (F-PAL) were efficiently prepared from p-bromobenzaldehyde and attached to the highly potent and specific V-ATPase inhibitors 21-deoxyconcanolide A (2) and bafilomycin A(1) (5), deriving from the natural product pool from Streptomyces producer strains. The labelled derivatives 17 and 18 were efficiently purified by fluorous solid-phase extraction. Functional biochemical assays with the V-ATPase holoenzymes proofed strong inhibition activities. So far, radioactive isotopes or biotin-tags have mainly been used for tracing compounds in photoaffinity studies. The C4F9- and C8F17-fluorous tags aim to enable advantageous separation and identification of labelled peptide fragments by fluorous chromatography followed by MS analysis. Therefore, F-PAL represents an innovative new concept for binding site determination and should significantly accelerate and simplify such biochemical investigations.