Patent ID: 7038042

Claim:
A compound represented by the formula: wherein Z is an electron-withdrawing group selected from the group consisting of a) a carboxyl group which may be optionally esterified, b) a group represented by the formula —(CO)NR 11 R 12 wherein R 11 and R 12 are respectively a hydrogen atom or an optionally substituted hydrocarbon group, and R 11 and R 12 may be bound to each other to form a 5- to 7-membered cyclic amino group together with a neighboring nitrogen atom, c) a group represented by the formula —(CO)R 4 wherein R 4 is a hydrogen atom or an optionally substituted hydrocarbon group, d) nitrile group, e) nitro group, f) a group represented by the formula —(SO m )R 5 , wherein m is an integer of 1 or 2 and R 5 is an optionally substituted hydrocarbon group, g) a group represented by the formula —PR 6 R 7 wherein R 6 and R 7 are each an optionally substituted hydrocarbon group, h) a group represented by the formula —(PO)(OR 8 )(OR 9 ) wherein R 8 and R 9 each are a hydrogen or an optionally substituted hydrocarbon group, i) an optionally substituted aryl group, j) an optionally substituted alkenyl group, k) a halogen atom and l) a nitroso group; ring A is an optionally substituted ring; the combined line of a broken line and and a solid line is a single bond or a double bond; R 3 is a hydrogen atom or an optionally substituted hydrocarbon group; and X is a divalent group is a straight-chain moiety of 4 or more atoms or a salt thereof.