The compound of formula [(R)aHL1-((R)cQ)m-L2H(R)b] can be obtained through reaction of the alkali metal compound [L1H(R)a]M??? or [LH(R)a]M??? or mixtures thereof with a compound of formula S-[(R)cQ]m-S, where S is a proper leaving group, such as halogen (Cl, Br, I), or aryl or alkyl sulphonate.