This compound, 1,3-Bis(benzyloxycarbonyl)-2-methyl-2-thiopseudourea, is a specialty reagent in organic synthesis, primarily used for the selective introduction of N-protected guanidino groups to primary amines. It is particularly valuable in peptide synthesis for constructing protected arginine side chains or other guanidine functionalities, transforming amines into stable N^ω-mono-Cbz-guanidines. This prevents unwanted side reactions during multi-step assemblies by masking the basicity of the guanidino moiety. The reagent's design allows for efficient reaction under mild conditions, with the dual Cbz groups providing stability and easy deprotection via hydrogenolysis. Furthermore, it serves as a key intermediate in the synthesis of biologically active compounds, such as pharmaceuticals (e.g., antiviral agents) and agrochemicals containing guanidine scaffolds.