The concomitant crystallization of two polymorphs of 1-de­oxy-[alpha]-D-tagatose

The crystalline form of 1-de­oxy-D-tagatose, C₆H₁₂O₅, is shown to be 1-de­oxy-[alpha]-D-tagatopyranose; the absolute configuration is determined by use of D-lyxono-1,4-lactone as the starting material. The title compound crystallized as concomitant polymorphs from a mixture of ethyl actate and methanol. Although the melting points of the materials differ by 7 K, the mol­ecular conformations are almost identical and, in both polymorphs, each mol­ecule is subject to four O-H...O hydrogen bonds.