The structure of sulphostin (1), a novel dipeptidyl peptidase IV (DPP-IV) inhibitor, is consisted of three key functional groups, including a characteristic amino (sulfoamino) phosphinyl group, on a piperidine ring. To examine the relationship between its structure and the inhibitory activity against DPP-IV, various analogues were synthesized and their activities were investigated. These results indicated that all of the functional groups on the ...