Patent ID: 7244841

Claim:
A compound of formula I wherein: X 1 , X 2 , X 3 and X 4 independently represent a hydrogen atom, a lipophilic moiety, a phenyl group, a lower alkyl, alkaryl or aralkyl group, or a cationic group of the following formula; —L —R 1 —N + (R 2 )(R 3 )R 4 wherein: L is a linking moiety or is absent; R 1 represents lower alkylene, lower alkenylene or lower alkynylene, which is optionally substituted by one or more substituents selected from lower alkyl, lower alkylene (optionally interrupted with oxygen), fluoro, OR 5 , C(O)R 6 , C(O)OR 7 , C(O)NR 8 R 9 , NR 10 R 11 and N + R 12 R 13 R 14 ; and R 2 , R 3 and R 4 independently represent H, aryl, lower alkyl, lower alkenyl or lower alkynyl, the latter three of which are optionally substituted by one or more substituents selected from lower alkyl, lower alkylene (optionally interrupted with oxygen), aryl, OR 5 , C(O)R 6 , C(O)OR 7 , C(O)NR 8 R 9 , NR 10 R 11 and N + R 12 R 13 R 14 Z is —CH or N; and Y 1 , Y 2 , Y 3 and Y 4 are absent or independently represent aryl, lower alkyl, lower alkenyl or lower alkynyl, the latter three of which are optionally substituted by one or more substituents selected from lower alkyl, lower alkylene (optionally interrupted with oxygen), aryl, OR 5 , C(O)R 6 , C(O)OR 7 , C(O)NR 8 R 9 , NR 10 NR 11 and N + R 12 R 13 R 14 ; and R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , R 12 , R 13 and R 14 independently represent H or lower alkyl provided that at least one of X 1 , X 2 , X 3 and X 4 is a cationic group as defined above and at least one of X 1 , X 2 , X 3 and X 4 is a hydrogen atom.