VITAMIN D DERIVATIVES WITH CYCLIC SUBSTRUCTURES IN THE SIDE CHAINS, METHOD AND INTERMEDIATES FOR THEIR PRODUCTION AND THEIR USE IN THE PREPARATION OF MEDICAMENTS

1. Vitamin D derivatives of general formula I, in which Y1 and Y2, independently of one another, each mean a hydrogen atom or a group -C(O)R5, and Y3 means a hydrogen atom or a hydroxy group, a halogen atom, a group -OC(O)R5 or an -OR5 group, whereby R5 stands for a saturated C1-C12 alkyl radical, and group Y3 can be present both in the 2.alpha.-situation and the epimeric 2.beta.-situation, R1 and R2 each mean a hydrogen atom or together an exocyclic methylene group, R3 and R4, independently of one another, each mean a hydrogen atom, or an alkyl group with 1 to 4 carbon atoms, Q means a straight-chain alkylene group with 1 to 5 carbon atoms, X1 and X2 together mean a double-bonded keto-oxygen atom or, independently of one another, a hydrogen atom, a hydroxy group, an -O(CO)R5 group, a fluorine, chlorine or bromine atom, whereby X1 and X2, not at the same time, each should be a hydroxy group or each an -O(CO)R5 group, Z means a carbocyclic or heterocyclic, optionally aromatic or heteroaromatic ring with 5 or 6 ring members or a condensed ring system that consists of a 5- and a 6-membered ring or two 6-membered rings, which can be substituted by one or more fluorine, chlorine, bromine or iodine atoms, one or more hydroxy groups, one or more COOR6 groups, one or more C1-C5 alkyl groups, which in turn can be substituted by one or more fluorine, chlorine, bromine or iodine atoms, C1-C6 alkoxy groups and/or COOR6 groups, whereby R6 stands for a C1-C6 alkyl group, a benzyl group or a phenyl group, and all possible epimers or diastereomers and mixtures thereof. 2. Compounds of general formula I according to claim 1, in which R3 or R4 means hydrogen, X1 and X2 together mean a carbonyl group, or X1 means a hydroxyl group or a fluorine atom and X2 means a hydrogen atom or X1 means a hydrogen atom and X2 means a hydroxyl group or a fluorine atom or X1 means an -OC(O)R5 group and R2 means a hydrogen atom or X1 means a hydrogen atom and X2 means an -OC(O)R5 group, and Z represents an aromatic ring cyclic system. 3. Compounds of general formula I according to claim 1, in which R3 or R4 means hydrogen, X1 and X2 together mean a carbonyl group, or X1 means a hydroxyl group or a fluorine atom and X2 means a hydrogen atom or X1 means a hydrogen atom and X2 means a hydroxyl group or a fluorine atom or X1 means an -OC(O)R5 group and X2 means a hydrogen atom or X1 means a hydrogen atom and X2 means an -OC(O)R5 group, and Z represents a heteroaromatic cyclic ring system. 4. Comp