Dibutyltin(IV) oxide reacts with the cantharidin analogue, 4′-(7-oxabicyclo [2,2,1]-5-heptane-2,3-dicarboximide) benzoic acid, A, to give the complexes [( p-C 8H 8NO 3–C 6H 4–COOBu 2Sn) 2O] 2 ( 1) and ( p-C 8H 8NO 3–C 6H 4–COO) 2SnBu 2 ( 2) which had been characterized by IR and 1H, 13C, 119Sn NMR. Single X-ray crystal structure analysis has been determined for compound ( 1), which was analogue to most other [(RCOOBu 2Sn) 2O] 2. The dimer features central of Bu 4Sn 2O 2 unit with the two Bu 2Sn groups being linked via bridging oxygen atom. Each tin atom adopts distorted trigonal bipyramidal structures via two carbons from a dibutyl moiety and three oxygen atoms from cantharidin derivative and bridging oxygen atom. In vitro tests show compounds 1 and 2 exhibit high cytotoxicity against P388 and HL-60.