The reaction of tartronic esters (1a-d) with 1,1'-carbonyl-di-(1,2,4-triazole), hydrazines or hydroxylamines produces 3-amino/3-alkoxy(aralkoxy)-2,4-dioxo-1,3-oxazolidine-5-carboxylic esters (5,6) which are structurally related to the fungicides Famoxadone (I) and Chlozolinate (II). Under suitable conditions the carboxylic ester of 6 can be converted to a carboxamide (7), carbohydrazide (8) or carbohydroxamic acid (9).