The ring-and side-chain-C-labeled probimane, 1,2-bis (4-morpholinomethy1-3,5-dioxopiperazin-1-yl) propane were synthesized from acetic acid-1-C in 4 steps and fromC-formaldehyde in 1 step respectively. The radiochemical yeild for the ring labeling was 28.1%; for the side-chain labeling was 18.5%.