Synthesis and photosynthetic electron transport inhibition of 2-substituted 6-fluorobenzothiazoles

Abstract

Series of ten N-substituted 2-(aminoethyl)-6-fluorobenzothiazoles inhibited photosynthetic electron transport in spinach chloroplasts. The inhibitory activity linearly increased with hydrophobic contributions (expressed as hydrophobic constants π) and molar volumes of individual substituents in C(2) position of 6-fluorobenzothiazole scaffold to the optima π ca. 2 and MV ca. 233 cm3, while for more lipophilic and/or bulkier derivatives PET inhibiting activity linearly decreased. The site of inhibitory action of the tested compounds is situated on the donor side of photosystem II, and interaction of these compounds with aromatic amino acid residues in photosynthetic proteins was confirmed by fluorescence spectroscopy. Synthesis and characterization of five new Nα-(alkoxycarbonyl)-N-[(1R)-1-(6-fluoro-1,3-benzothiazol-2-yl)ethyl]-l-phenylalaninamides is presented as well.