The present invention relates to analogues of vitamin D, which lack the combined presence of the trans-fused six-membered C-ring and of five-membered D-ring, but still possess a central part consisting of a substituted chain of five atoms, atoms which correspond to positions 8, 14, 13, 17 and 20 of vitamin D, and at the ends of which are connected, at position 20 a structural moiety representing part of the side-chain of vitamin D or of an analogue of vitamin D, and at position 8 the .DELTA.(5,7)-diene moiety connected to the A-ring of the active 1-alpha-hydroxy metabolite or of an established vitamin D analogue, to their preparation process, to preparation intermediates, to pharmaceutical preparations comprising these compounds and to their use in medicine.