| abstract |
The present invention relates to a compound of formula (I), in which, alpha) Ra denotes hydrogen or a silyl group; Rb denotes a group of formula -ORc, in which Re denotes hydrogen or alkyl; and Rc and Rb together denote a bond; or beta) Ra and Rd denote hydrogen or a silyl group; and Rb and Rc together denote an imino group of formula = N-Y, in which Y denotes alkyl, aryl, or heterocyclyl; y) Rd denotes hydrogen or a silyl group; Ra denotes hydrogen, if Rd denotes hydrogen; or, Ra denotes hydrogen or a silyl group, Rd denotes a silyl group, and Rb and Rc together denote the oxo group; in free form or in the form of a salt. |