The invention concerns compounds of formula (I) wherein in particular G presents the —N(CH
3
)
2
—, —N(C
2
H
5
)
2
-group or N-pyrrolidine: n is an integer equal to 1 or 2: R
1
, R
2
and R
3
independently of one another, represent a hydrogen atom or a methyl group, the successive unsaturated units capable of being moreover identical or different, provided that at least one of the substituents R
1
, R
2
and R
3
is different from H: and Y
1
and Y
2
represent each a —COOCH
3
group or a —COOC
2
H
5
group.
本发明涉及式 (I) 的化合物,其中 G 特别呈现-N(CH
3
)
2
-、-N(C
2
H
5
)
2
-基团或 N-
吡咯烷: n 是等于 1 或 2 的整数: R
1
, R
2
和 R
3
分别代表一个氢原子或一个甲基,连续的不饱和单元可以相同或不同,条件是至少有一个取代基 R
1
, R
2
和 R
3
不同于 H
1
和 Y
2
各代表一个 -COOCH
3
基团或-COOC
2
H
5
基团。