Caffeic acid derivatives and pharmaceutical compositions containing the same

A caffeic acid compound represented by the following formula (I):

• ##STR47## wherein one of R.sup.1 and R.sup.2 is a member selected from the group consisting of a hydrogen atom, a C.sub.1 -C.sub.6 alkyl group, a group --CO.sub.2 R.sup.4, R.sup.4 representing a C.sub.1 -C.sub.12 alkyl group, a C.sub.6 -C.sub.10 aryl group, a hydrogen atom or a C.sub.7 -C.sub.6 alkyl group and R.sup.6 representing a hydrogen atom or a C.sub.1 -C.sub.6 alkyl group, and the other of R.sup.1 and R.sup.2 is the group --CO.sub.2 R.sup.4 or the group --CONR.sup.5 R.sup.6, or R.sup.1 and R.sup.2 are coupled together to represent a 5-membered ring so formed, Y represents a vinylene group, an oxygen atom or a sulfur atom, X represents a substituted or unsubstituted C.sub.6 -C.sub.10 aryl group, or a substituted or unsubstituted C.sub.7 -C.sub.12 aralkyl group, m means an integer of 0-8, n denotes an inter of 0 or 1, and R.sub.3 represents a hydrogen atom, a hydroxyl group, a group --OCO.sub.2 R.sup.7, R.sup.7 representing a C.sub.1 -C.sub.12 alkyl group, a C.sub.6 -C.sub.10 group, a hydrogen atom or a C.sub.7 -C.sub.12 aralkyl group, or a group --OCONR.sup.8 R.sup.9, R.sup.8 representing a C.sub.1 -C.sub.6 alkyl group and R.sup.9 representing a hydrogen atom or a C.sub.1 -C.sub.6 alkyl group, or a pharmaceutically acceptable salt thereof.