Abstract: Pharmaceutical preparations containing alkyl and alkenyl glycerol ethers substituted in the side chain and esters thereof having the general formula ##STR1## wherein R.sup.1 and R.sup.2 are the same or different in each is selected from the group consisting of hydrogen and aliphatic acyl groups of at most 24 carbon atoms, one of R.sup.3 and R.sup.4 being hydrogen and the other being selected from the group consisting of straight, branched, saturated and unsaturated alkoxy groups of at most seven carbon atoms, and R.sup.5 is selected from the group consisting of straight, branched, alkyl and alkenyl groups of 4-21 carbon atoms. The compounds are useful as antibiotics in the treatment of infectious diseases and for inhibiting the growth of tumors.