Ada-(Ahx)3-(Leu)3-vinyl sulfone

A new class of proteasome inhibitors, considerably extended in comparison with the commonly used fluorescent substrates and peptide-based inhibitors, has been prepared. Evaluation of these new compounds revealed a set of highly potent proteasome inhibitors that target all individual active subunits with comparable affinity, unlike the other inhibitors described to date. These compounds are more potent in living cells than their shorter peptide vinyl sulphone counterparts. Modification of the most active compound, adamantaneacetyl-(6-aminohexanoyl)3-(leucyl)3-vinylmethyl-sulphone itself capable of proteasome inhibition in living cells, afforded a new set of radio- and affinity labels.