LK6-A derivatives represented by general formula (I) and pharmacologically acceptable salts thereof, which exhibit immunosuppressive, cytostatic and antitumor effects and so on, wherein R 1 is a lower alkanoyl or acryloyl group which may be substituted with, e.g., lower alkoxy, or the like; R 2 is hydrogen, halogeno or the like; R 2' is hydrogen, or R 2' together with R 3 forms a bond; R 3 is optionally substituted lower alkanoyl, or R 3 together with R 2' forms a bond; R 4 and R 5 are each hydrogen, optionally substituted lower alkanoyl or the like; R 6 is hydrogen or the like; and R 7 and R 8 are each hydrogen, optionally substituted lower alkanoyl or the like, with the proviso that LK6-A corresponding to a compound of general formula (I) where R 1 is (E)-methoxyacryloyl; R 2 , R 4 , R 5 , R 6 and R 7 are each hydrogen; R 8 is acetyl; and R 2' and R 3 together form a bond is excepted.