| abstract |
1. Compounds of the formula see diagramm : EP0086944,P10,F1 wherein R signifies C1-4 -alkyl, 1-C1-2 -alkoxy-C1-4 -alkyl or C2-4 -alkenyl, R**1 , R**2 and R**3 represent hydrogen, C1-5 -alkyl or C2-4 -alkenyl or C1-4 -alkylidene, whereby 2 or 3 of the residues R**1 , R**2 , R**3 and R**4 are hydrogen. |