The synthesis of D-mannuronolactone acetonide 1 is described from alginic acid and provides an efficient route for the manipulation at C-5 of mannose. Reduction gives a new acetonide of mannose, 1,2-O-isopropylidene-β-D-mannofuranose which, on further acetonation, gives 1,2:5,6-di-O-isopropylidene-β-D-mannofuranose [giving easy access to C-3 OH of mannose] together with a small amount of 1,2:3,5-di-O-isopropylidene-β-D-mannofuranose. Some silylated derivatives of mannuronolactone allow immediate access to the C-6 of mannose. Such intermediates are likely to be of value in the synthesis of derivatives of mannose.
