The present invention relates to compounds (I) And Compounds of formula (II) Wherein R 2a and R 2b are independently of each other a linear alkyl group having from 1 to 4 carbon atoms, R 1a , R 1b , R 3a to R 6a and R 3b to R 6b are independently of each other a hydrogen atom or a linear alkyl group having from 1 to 4 carbon atoms, / RTI
展开▼