Oxidation—continued with lead tetraacetate

Ethyl 2-(D-amiino-tetrahydroxybutyl)-5-methyl-4-furoate (5.5 g.) is mixed with 80 ml. of dry benzene and 20 ml. of glacial acetic acid, and cooled in ice plus water. While stirring and cooling, 182 g. of lead tetraacetate (purity, 99.7%)62 is added during about sixty minutes stirring is continued until all the oxidant has been consumed. The lead dioxide is then removed by filtration, and the benzene solution is extracted twice with water.58 The benzene layer is dried with calcium chloride and the solvent is evaporated under diminished pressure, giving an oily residue which rapidly crystallizes in colorless plates yield, 3.6 g. (quantitative). The product is purified by recrystallization from dilute acetic acid or by steam distillation m.p., 57°. 

Hockett, Nickerson, and Reeder,91 using a very large excess of lead tetraacetate in acetic acid at 20°, observed an oxidation pattern for methyl a-D-mannofuranoside consistent with that noted by Criegee. One mole of reagent per mole was consumed very rapidly, and further oxidation was slow, as expected for the sequence XXV — XXVII. Presence of a small but finite amount of XXVI was thought to account for the slow, continuing oxidation. 

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