| abstract |
A piperazinedione derivative of formula (I), wherein R<1> is: (i) a group alpha , wherein p is 0 or 2; (ii) a 5- or 6-membered heterocyclic ring containing at least one heteroatom selected from O, N and S, which group may be fused to a benzene ring; R<2> is H, C1-C6 alkyl optionally substituted by a group -N(R<11>R<12>) as defined above, C3-C6 cycloalkyl, C2-C6 alkenyl, -COOR<11> wherein R<11> is as defined above or a phenyl ring as defined under (i) above, but is other than H when R<1> is unsubstituted phenyl; and one of R<3> and R<4> is hydrogen and the other is a group of formula (A), wherein q is an integer of 1 to 4, r is 0 or 1 and R<5> and R<6>, which may be the same or different, are each H or C1-C6 alkoxy, or R<5> and R<6> together form a methylenedioxy group; <u>-----</u> is a double bond or, when R<1> is as defined under (i) above, is a double bond or a single bond; and pharmaceutically acceptable salts thereof have activity as modulators of multi-drug resistance. |