The present inventors intended to search for substances that can regulate the expression of a molecular chaperone, GRP78, using the expression of GRP78 as an indicator. As a result, a novel tetronic acid derivative, versipelostatin compound (also known as JL68) shown in formula (I) having the activity of suppressing GRP78 expression was isolated from the metabolite of Streptomyces versipellis strain 4083-SVS6. Versipelostatin can be obtained from the culture supernatant by culturing the above-mentioned Streptomyces versipellis strain 4083-SVS6 ##STR00001##