Ethyl 2-methyl-4-(diethoxyphosphoryl)-4,7-dihydro-5Н-thiopyrano[3,4-b]furan-5-carboxylate was synthesized. It was shown that at elevated temperatures it is acetylated in presence of tin tetrachloride and chloromethylated with paraformaldehyde–hydrogen chloride system in the presence of zinc dichloride at the positon 3 of heterocyclic system. Reaction of chloromethyl derivative with N-, S- and О-nucleophiles was studied.