Synthesis and characterization of 3-methyl-6-[(propyn-yloxy)meth-yl]-1,4-dioxane-2,5-dione.

The number of known asymmetrically substituted hemilactides, important precursors for obtaining regular derivatives of polylactide polymers, is still limited and structural characterization of most of them is incomplete. In the title racemic 1,4-dioxane-2,5-dione derivative, C9H10O5, the hemilactide heterocycle exhibits a twist-boat conformation. The bulkier propynyloxymethyl group is in an axial position with a gauche conformation for the CH2-O-CH2-C segment. In the crystal, mol-ecules are linked by pairs of C-H⋯O hydrogen bonds, forming inversion dimers. The dimers are linked by further C-H⋯O contacts, forming a three-dimensional structure.