| 摘要 |
There are described compounds of formula I, <IMAGE> I in which R5 to R8 may be a variety of substituents, OR AN ADJACENT PAIR OF R5, R6, R7 and R8 form a chain -COCH=C(COOH)NRh-, OR ONE OF R5, R6, R7 and R8 form a group of formula II, <IMAGE> II in which Ra, Rb and Rc have the same significances as R5, R6, R7 and R8, X is an optionally interrupted or substituted hydrocarbon chain, Rg and Rh, which may be the same or different are each alkyl, alkenyl, phenyl-alkyl, alkanoyl, benzoyl or phenylalkanoyl, OR Rg and R8 and/or Rh and Rc in formula II, together form a chain -(CH2)n-, and n is 2, 3 or 4.
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