Coriose (D-altro-3-heptulose) (I) was synthesized by the lead tetraacetate oxidation of hydrolyzate of the mother liquor of 1, 3 : 5, 7-di-O-ethylidene-3-C-formyl-D-glycero-D-talo-heptitol-3 (1), 6-pyranose (IV) which was derived from 2, 4-O-ethylidene-D-erythrose (V) by the aldol condensation.