A compound provided by the present invention, of the formula ##STR1## wherein R.sup.1 is C.sub.14-20 alkyl; R.sup.2, R.sup.3 and R.sup.4 are independently hydrogen or C.sub.1-5 alkyl, or ##STR2## represents a cyclic ammonio group; and A is C.sub.2-5 alkylene, and a pharmaceutically acceptable salt thereof, are useful as a anti-tumor agent.