A number of chiral racemic and enanthiopure thiophosphorylatedthioureas were synthesized by the reaction of 2-aminobutan-1-ol and 1-(a-aminobenzyl)-2-naphthol with O,O-diethyl thiophosphoryl isothiocyanate. It was found that such thioureas undergo the cyclizationreaction under basic conditions with hydrogen sulfide elimination and the formation of thiophosphorylated oxasines. X-Ray single crystal