Synthesis and evaluation of eight-membered cyclic pseudo-dipeptides.

In the course of the development of calpain inhibitors, we report the synthesis of eight-membered cyclic pseudo dipeptides closely related to the known inhibitor SJA6017. The ring closure was effected by metathesis of the diallyl-substituted dipeptides 6 and 7. The formation of the dipeptides under kinetic control leads to the preferential formation of the unlike diastereomer 7 over the like diastereomer 6. The relative configuration of the diastereomers was determined by NMR and modeling studies of the related cyclic compounds 8 and 9 and their derivatives. The compounds proved not to inhibit calpain.