| abstract |
A compound of formula wherein R 1 and R 2 are the same or different and denote hydrogen, alkyl, halogen, methoxycarbonyl, ethoxycarbonyl, alkoxy or alkanoyl in any position, R 6 is hydrogen, methylsilyl ethyl, R 3, R 4 and R 5 are the same or different and separately denote hydrogen, methyl, methoxy, ethoxy, methoxyethoxy or ethoxyethoxy, all of which do not simultaneously represent hydrogen and when two of the substituents R3, R4 and R5 represent hydrogen, the third is other than methyl or a therapeutically acceptable salt thereof. |