. . "xy group.Halogen is, for example, halogen of atomic number up to and including 35, such as chlorine or fluorine, furthermore bromine.Lower alkoxycarbonyl is, for example, C.sub.1 -C.sub.7 alkoxycarbonyl, preferably C.sub.1 -C.sub.4 alkoxycarbonyl, such as methoxycarbonyl, ethoxycarbonyl, propyloxycarbonyl, isopropyloxycarbonyl or butyloxycarbonyl, but can also beisobutyloxycarbonyl, secondary buty" . . .