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X-ray crystallography firmly established the relative stereochemistry of the title compound, C17H22N2O3. The absolute configuration was determined by use of 2-C-methyl-D-ribonolactone as the starting material. The compound exists as O—H
N hydrogen-bonded chains of molecules running parallel to the a-axis.
N hydrogen-bonded chains of molecules running parallel to the a-axis.organic compoundsOpen access
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X-ray crystallography confirmed the formation, structure and relative stereochemistry of the title compound, C15H19NO3, which contains a sterically congested four-membered azetidine ring system. The absolute configuration was determined by the use of L-arabinose as the starting material.
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The six-membered boronate ester ring of the title compound, C13H16BNO6, adopts an envelope conformation with the C atom bearing the dimethyl substituents at the flap. The O—B—C—C torsion angles between the boronate group and the benzene ring are 72.5 (2) and 81.0 (2)°. The 4-nitrobenzoate unit adopts a slightly twisted conformation, with dihedral angles between the benzene ring and the nitrate and methyl ester groups of 17.5 (2) and 14.4 (3)°, respectively. In the crystal, inversion-related pairs of molecules show weak π–π stacking interactions [centroid–centroid distance = 4.0585 (9) Å and interplanar spacing = 3.6254 (7) Å].
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The absolute stereochemistry of the title compound, C9H15NO7, was determined from the use of D-glucuronolactone as the starting material. The compound crystallizes as the zwitterion. The five-membered ring adopts an envelope conformation with the –CH2OH-substituted C atom forming the flap. An intramolecular N—HO hydrogen-bond occurs. In the crystal, the compound exists as a three-dimensional O—HO intermolecular hydrogen-bonded network with each molecule acting as a donor and acceptor for four hydrogen bonds.
O hydrogen-bond occurs. In the crystal, the compound exists as a three-dimensional O—HO intermolecular hydrogen-bonded network with each molecule acting as a donor and acceptor for four hydrogen bonds. 
