Simple approach to highly functionalized trisubstituted tetrahydro pyrimidine-2,4-diones from perhydropyrazino [1,2 -f] pyrimidine -3,6,8 -trione precursors

Unprecedented trisubstituted tetrahydropyrimidine-2,4-diones were easily synthesized in two steps involving Boc-amide protection and controlled ring opening, from perhydropyrazino[1,2- F]pyrimidine-3,6,8-triones. These bicyclic derivatives were prepared by reaction of 2-oxopiperazines derived from dipeptides with isocyanates, followed by cyclization. The monocyclic pyrimidinone derivatives were further elaborated to potential CCK ligands that have contributed to a better understanding of the structural requirements for efficient binding at the CCK 1 receptor.