The present invention relates to calcium salts of compounds of the general formula (I)whereinX is selected from the group consisting of CH2, S, or O;D is O or S;R8 is hydrogen or alkyl;E is an optionally substituted phenylene group;Y is a monocyclic or bicyclic substituted or unsubstituted 6-9 membered ring system which may contain one or more heteroatoms selected from N or S and which contains at least one aromatic ring;n is 0 or 1, andq is 0 or 1;with the proviso that compounds wherein X═CH2, q=0, Y=unsubstituted phenyl and E=unsubstituted phenylene are excluded;or a hydrate thereof.