A series of derivatives of the 2-deoxy analogue of beta-KDO (2,6-anhydro-3-deoxy-D-glycero-D-talo-octonic acid; ammonium salt, 2) has been synthesised as potential inhibitors of CMP-KDO synthetase, starting from methyl 2,6-anhydro-3-deoxy-4,5:7,8-di-O-isopropylidene-D-glycero-D-talo- octonate and replacing the CO2Me group attached to C-2 variously by CONH2, CONHOH, CH2OH, CH2PO(OH)(O-NH4+), COCH2PO(OH)(O-H3N+pheny), CH2CO2-NH4+, CON-HCH2CO2-NH4+, CONHBn, CONHHexyl, CO2Bn, and CO2Hexyl. Of these derivatives, the hydroxamic acid (CONHOH) was the best inhibitor of CMP-KDO synthetase, but was less potent than 2.