Alkyl levulinates as `green chemistry' precursors: butane-1,4-diyl bis­(4-oxo­pentan­oate) and hexane-1,6-diyl bis­(4-oxo­pentan­oate)

Levulinic acid derivatives are potential `green chemistry' renewably sourced mol­ecules with utility in industrial coatings applications. Suitable single crystals of the centrosymmetric title compounds, C₁₄H₂₂O₆ and C₁₆H₂₆O₆, respectively, were obtained with difficulty. The data for the latter hexane-1,6-diyl compound were extracted from the major fragment of a three-component twinned crystal. Both compounds crystallize in similar-sized unit cells with identical symmetry, utilizing the same weak nonconventional attractive C-H...O(ketone) hydrogen bonds via C(4) and C(5) motifs, which expand to R²₂(30) ring and C²₂(14) chain motifs. Their different packing orientations in similar-sized unit cells suggest that crystal growth involving packing mixes could lead to inter­growths or twins.

Translationally related nearly identical mol­ecules: 4-meth­oxy­phenyl 4-O-[6-O-acetyl-2-azido-3-O-benzyl-2-de­oxy-4-O-(fluoren-9-yl­meth­oxycarbon­yl)-α-D-gluco­pyranos­yl]-2-O-benzoyl-3-O-benzyl-6-O-chloro­acetyl-β-D-gluco­pyran­oside

The title compound, C₅₉H₅₆ClN₃O₁₆, is an important dissacharide precursor to novel therapeutics for the treatment of Alzheimer's disease. It crystallizes with two independent enantio­merically identical mol­ecules in almost exactly the same orientation in the cell, being one half cell-edge apart. Apart from the conformation of a single benzyl group, the mol­ecules are superimposable. They are bound efficiently using complementary C—H...O(carbonyl) hydrogen bonds, principally along the `duplicating' axis. The absolute configurations were determined.