Synthesis of a [C-14]-labelled photoactivatable cyclic tetrapeptide: [carbonyl-C-14]-4-benzoylbenzoyl MeSer(1)-tentoxin.

The synthesis of a new photochemical probe for labelling tentoxin I binding sites in the soluble part of chloroplast F0F1 ATPsynthase is described. [C arbonyl-C-14]-4-benzoylbenzoyl MeSer(1)-tentoxin 6 was synthesised by coupl ing MeSer(1)-tentoxin 2 with [carbonyl-C-14]-4-benzoylbenzoic acid 3, itsel f obtained by coupling [1-C-14]-benzoyl chloride with the dilithio derivati ve of 4-bromobenzoic acid (9). Photolysis of the probe in methanolic soluti on occurs readily upon irradiation with UV light at 366 nm.