TAN-1057A-D, dipeptides isolated from bacteria Flexibacter sp. PK-74 and PK-176, are new antibiotics with potent antibacterial activity against methicillin-resistant Staphylococcus aureus. We describe, in detail, the total synthesis of TAN-l057A-D by a convergent route featuring a new method to construct the cyclic amidinourea functional group.