A series of 3-alkoxy(phenyl)thiophosphorylamido-2-(per-O-acetylglycosyl-1'-imino)thiazolidine-4-one derivatives were prepared by the reaction of 1-alkoxy(phenyl)thiophosphoryl-4-(per-O-acetylglycosyl) thiosemicarbazides with ethyl bromoacetate. (1)H/(13)C HMBC measurements corroborated by X-ray crystallographic results revealed the exclusive regioselectivity of these ring closures toward the N-2 position of the thiosemicarbazide moiety. The bioactivity data of 3a-k suggest that the thiazolidine-4-one ring is critical for the herbicidal and fungicidal activities.