Dimethyl cis-2-methyl-3-p-tolylisoxazolidine-4,5-dicarboxylate

In the molecule of the title compound, C15H19NO5, the isoxazole ring adopts an envelope conformation. In the crystal structure, weak intermolecular C—H⋯O and C—H⋯N hydrogen bonds link the molecules, in which they may be effective in the stabilization of the structure.

In the molecule of the title compound, C 15 H 19 NO 5 , the isoxazole ring adopts an envelope conformation. In the crystal structure, weak intermolecular C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds link the molecules, in which they may be effective in the stabilization of the structure.

Comment
Nitrones are members of a class of compounds which are commonly used as precursors in the syntheses of natural products (Tufariello, 1984), as spin-trapping reagents in the identification of transient radicals (Villamena & Zweier, 2004), and as therapeutic agents (Floyd & Hensley, 2000;Inanami & Kuwabara, 1995) such as in the case of disodium-[(tert-butylimino) -methyl]benzene-1,3-disulfonate N-oxide (NXY-059) which is in clinical trials in the USA for the treatment of neurodegenerative disease (Becker et al., 2002). In recent years, it has become clear that reactive oxygen species (ROS) (e.g., radicals: O 2 . -, HO., HO 2 ., RO 2 ., RO., CO 3 . -, and CO 2 . -; and non-radicals such as H 2 O 2 , HOCl, O 3 , 1 O 2 , and ROOH) are critical mediators in cardiovascular dysfunction, neurodegenerative diseases, oncogenesis, lung damage and aging, to name a few (Halliwell, 2001a;2001b;Zweier & Talukder, 2006). Electron paramagnetic resonance (EPR) spectroscopy has been an indispensable tool for the detection of these ROS via spin trapping [Villamena & Zweier, 2004;Janzen, 1971;Janzen,1980;Janzen & Haire, 1990;Villamena et al., 2007). The nitrone-based spin traps, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 5diethoxyphosphoryl-5-methyl-pyrroline N-oxide (DEPMPO) and 5-ethoxycarbonyl-5-methyl-pyrroline N-oxide (EMPO), are the most commonly used spin-trapping reagents and have contributed significantly to the understanding of important free radical-mediated processes in chemical, biochemical, and biological systems in spite of their many limitations. The 1,3-dipolar cycloaddition of nitrones and alkenes is a powerful synthetic device that allows up to three new stereogenic centers to be assembled in a stereospecific manner in a single step (Confalone & Huie, 1988;Torssell, 1988;Frederickson, 1997;Gothelf & Jorgensen, 1998). The syntheses of isoxazolidine derivatives is an important subject in organic chemistry because they are found in the structure of most natural compounds and drugs. In recent years, isoxazolidine derivatives have been synthesized in high yield via intermolecular cycloaddition of N-methylnitrone with disubstituted olefins and are employed for biological evaluation. In view of the importance of the isoxazolidines, we report herein the crystal structure of the title compound.
In the molecule of the title compound ( Fig. 1), the bond lengths (Allen et al., 1987) and angles are within normal ranges.
In the crystal structure, weak intermolecular C-H···O and C-H···N hydrogen bonds (Table 1) link the molecules, in which they may be effective in the stabilization of the structure.

Refinement
H atoms were positioned geometrically, with C-H = 0.93, 0.98 and 0.96 Å for aromatic, methine and methyl H, respectively, and constrained to ride on their parent atoms, with U iso (H) = xU eq (C), where x = 1.5 for methyl H and x = 1.2 for all other H atoms. The absolute structure could not be determined reliably, and 1474 Friedel pairs were averaged before the last cycle of refinement. Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.