. . . . "imethylene or tetramethylene, in which R6 can also be a hydrogen atom, R7 and R8 are a hydrogen atom or independently have the meaning of R5 and R6, and R9 and R10 are a hydrogen atom, or independently have the meaning of R5 and R6, or R7 and R9 in formula VIIIa together are trimethylene or tetramethylene." . .