disclosed is a method for the preparation of a β - thiolactam compound , i . e . a 7 - substituted - 2 - oxa - 7 - azabicyclo - heptan - 6 - thione , represented by the general formula ## str1 ## in which r is an alkyl or aryl group , having usefulness as an intermediate for the synthesis of various biologically active compounds . the compound can be prepared by the reaction of an isothiocyanate compound r -- ncs , r being the same as above , and 2 , 3 - dihydrofuran , preferably , under pressurization up to 2000 atmospheres or higher at an elevated temperature .