Lipid A 3-etheranalogues were synthesized from allyl 2-deoxy-4,6-O-isopropylidene-2-trifluoroacetamido-alpha-D-glucopyr anoside and 3,4,6-tri-O-acetyl-2-trifluoroacetamido-alpha-D-glucopyranosyl bromide. The compound lost completely the endotoxic activity.