or a pharmaceutically suitable salt thereof, wherein, R1 and R2 independently are hydrogen, deuterium, aryl, hetero aryl, C1-C8 alkyl, optionally being substituted with one or more substituents independently being R3, R3 is an aryl, hetero aryl, fluorine(s), a C1-C6 alkyl containing one or more fluorine, a C1-C6 alkyl containing one or more deuterium, a C1-C6 alkyl containing hydroxy, the aryl and heteroaryl optionally being substituted with one or more halogen, a fluorinated alkoxy, a fluorinated alkyl, a sulfonyl, one or more deuterium, a C1-6 alkyl, a C1-6 alkoxy, a nitrile, or R3 is a C1-6 alkyl optionally substituted with one or more of the following groups: COOR4, OCOR4, CONR5R6, NR5COR6, OR4; wherein, R4 is a C1-10 alkyl optionally substituted with one or more fluorine, deuterium, alkoxy, arylcarboxylate, alkyl carboxylate; R5 and R6 are independently selected from hydrogen, alkyl or they may together form a 4-8 membered carbon ring; or R1 and R2 form a 3-10 membered carbon ring optionally comprising O or N and optionally substituted with a C1-10 alkyl or aryl, hetero aryl optionally substituted with R3.