1-Deoxy-D-xylulose (= 1-deoxy-D-theropentulose) is a precursor of thiamin (Vitamin B1) and of pyridoxine (Vitamin B6) in bacteria. The synthesis of a [2,3-13C2] bond-labeled sample of the compound, to be used for investigations of the biosynthesis of the two vitamins, is described. In aqueous solution 1-deoxy-D-xylulose exists mainly as the open chain ketone. In methanol solution the compound exists as a mixture of the open chain ketone and the two corresponding epimeric furanoses. In acid solution the compound yields a dimeric anhydride, di-β-1-deoxy-D-xylulofuranose 2,3′:3,2′-dianhydride, whose structure was established by X-ray crystallography. Keywords: [2,3-13C2]-1-deoxy-D-xylulose, di-β-1-deoxy-D-xylulofuranose 2,3′:3,2′-dianhydride, 5-O-benzyl-3,4-O-isopropylidene-1-deoxy-D-xylulose, 4-O-benzyl-2,3-O-isoproylidene-D-threose.