A method of producing an aminobutene derivative of formula (I) by allowing a butenol derivative of formula (II) to react with an amide derivative of formula (III) is disclosed. The aminobutene derivative of formula (I) can be deprotected to produce an aminobutene derivative of formula (I-1) or an aminobutene derivative of formula (I-2): ##STR1## The aminobutene derivative of formula (I-A) can also be deprotected to produce the aminobutene derivative of formula (I-B). Any or all of the above aminobutene derivatives are useful as intermediates for producing anti-ulcer drugs, and anti-ulcer drugs having an inhibitory effect on gastric acid secretion based on the antagonism against histamine H.sub.2 receptor.