Preparation and biological properties of biotinylated PhTX derivatives.

We report the synthesis of several highly functionalized biotinylated philanthotoxin (PhTX) analogues (7, 8, 10, 13-16) designed on the basis of earlier structure-activity relationship studies. Despite the extensive modifications, the binding to nicotinic acetylcholine receptor (nAChR) is in the low micromolar range according to an inhibition assay using 3H-thienylcyclohexyl-piperidine (TCP). A patch clamp functional assay gave comparable results. Compounds exemplified by 16, which consists of a biotinylated ligand linked to a bifunctional photoaffinity probe (BPP), represent a new type of probe which should find use in photo-crosslinking studies of ligand receptor interactions.