[1,2:3,4:5,6-tri-O-isopropylidene-D-gluconolactone as a substrate in models synthesis of Kdo].

Several approaches towards 2-keto-3-deoxy-D-manno-octulosonic acid (1) have been proposed. The only one which gave satisfactory results led to 2,3-dideoxy-5,6:7,8-di-O-isopropylidene-D-manno-octulosonic acid (39). This direct precursor of 2-keto-3-deoxy-D-manno-octulosonic acid (1) which was synthesized from the readily available 1,2:3,4:5,6-tri-O-isopropylidene-D-gluconate (2) in 6 steps.