A method of preparing a compound of formula (I): wherein: a first group selected from R1, R2 and R3 is an amino- or N-acylamino monosaccharide moiety, the acyl group having 1 to 6 carbon atoms, or an oligosaccharide chain comprising 2 to 4 monosaccharide moieties, at least one of which is an amino- or N-acylamino monosaccharide moiety; a second group selected from R1, R2 and R3 is a alkanoyl and alkenoyl acyl group having 3 to 40 carbon atoms; and a third group selected from R1, R2 and R3 is hydrogen, the method comprising contacting a monoacylglycerol, the acyl moiety thereof being a saturated or unsaturated acyl group having 3 to 40 carbon atoms, or an activated derivative thereof, with a source of amino- or N-acylamino monosaccharide moiety, or an activated derivative thereof, and, if required, a source of unsubstituted monosaccharide moiety, or an activated derivative thereof, optionally in the presence of a suitable catalyst or activating agent, is described.