Treatment of methyl 2,4,5,7,8-penta-O-acetyl-3-deoxy-cr-D-manno-oct-2ulopyranosonic acid, or its methyl ester, with refluxing methanolic O.lM hydrogen chloride for 16 h gave 95% of methyl (methyl 3-deoxy-a-D-manno-act-2-ulopyranosid)onate.
Acetylation of the methyl ester of 3-deoxy-D-manno-act-2ulosonic acid (KDO) gave mainly methyl 2,4,6,7,8-penta-O-acetyl-3-deoxy-cy,P-Dmanno-act-2-ulofuranosonate.
Treatment of this mixture with methanolic 0.02~ hydrogen chloride at room temperature gave methyl (methyl 3-deoxy-a&Dmanno-act-2-ulofuranosid)onate and the corresponding 4-acetates which were isolated by reverse-phase column chromatography of their 7,8-0-isopropylidene derivatives. Confirmation of the position of the isopropylidene group was obtained by acetylation to give methyl (methyl 4,6-di-0-acetyl-3-deoxy-7,8-O-isopropylidene-a$-D-manno-act-2-ulofuranosid)onate.
The furanose anomers were differentiated primarily by J,,, values (a -6.1 Hz, p -2.2 Hz). The anomeric configuration in the furanose series has been assigned on the basis of optical rotation.