To predominantly synthesize trans 4-methylthio-3-butenyl isothiocyanate having an antibacterial action.

To predominantly produce trans 4-methylthio-3-butenyl isothiocyanate useful as a natural substance having antibacterial activity, first, one carbon-carbon bond is added to a 1,3-dihalopropane to form a 4C 4-halogeno-1-methylsulfinyl-1-methylthiobutane, and from this substance, an unsaturated intermediate having a halogen at one end and a methylthio group at the other end is formed. Successively, after carbon-nitrogen bonding is achieved at the carbon atom to which the halogen (X1) of the above unsaturated intermediate is bonded, deprotection is performed to form an amine compound intermediate, and lastly, the amine compound intermediate is isothiocyanated to predominantly synthesize the target trans 4-methyl-3-butenyl isothiocyanate.