Five sparsomycin analogs (9-13) were prepared and examined for their ability to inhibit deoxyribonucleic acid (DNA) synthesis in L5178Y lymphoma cells. All of the compounds showed significant activity in the DNA synthesis assay. The compounds having R_C configuration exhibited almost the same activities independently of the configuration at the sulfoxide sulfur atom. Among the S_C isomers, the R_S configuration was advantageous for the appearance of activity.