| abstract |
Compounds of formula (I) (See formula) in which R1 and R2 together represent O and R3 and R4 together represent O, or R1 means hydrogen, hydroxy or alkoxy- (C1-C4), R2 means hydrogen and R3 and R4 represent together O, or R1 and R2 together represent O, R3 means hydrogen, hydroxy or alkoxy- (C1-C4) and R4 means hydrogen R5 and R6 represent hydrogen and R7 and R8 together represent (See formula) in which R9 means halogen, trifluoromethyl or methyl. |