Blockading the interaction of programmed death-1 (PD-1) protein with its ligands 
(PD-Ls, such as PD-L1) was proved to be a pathway for suppressing the 
development of tumors and other degradations of biological species. Thus, 
finding PD-1 inhibitors situated at the convergence point of drug discovery. In 
addition to some monoclonal antibodies applied to treat cancers clinically, the 
screening of organic molecules for hindering the interaction of PD-1 with PD-L1 
became an efficient strategy in the development of PD-1 inhibitors. We herein 
applied resorcinol and 3-hydroxythiophenol as the core to link with 
N,N-dimethylcarbamate and other alkyl-substituted amines to afford 13 
amine-appended phenyl dimethylcarbamates (AAPDs). The test for blockading the 
combination of PD-1 with PD-L1 revealed that abilities of 13 AAPDs were higher 
than that of sulfamethizole, a successful PD-1 inhibitor. In particular, large 
hydrophobic substituents at amine moiety or a nitro at resorcinol skeleton 
enhanced the inhibitory effect of AAPD even higher than that of 
sulfamethoxypyridazine, another successful PD-1 inhibitor. The present results 
may provide valuable information for further investigation on synthetic PD-1 
inhibitors.