(2R,6S)-tert-Butyl 2-(benzhydrylcarbamoyl)-6-methylmorpholine-4-carboxylate

The title compound, C24H30N2O4, was obtained by the reaction of (2R,6S)-4-(tert-butoxycarbonyl)-6-methylmorpholine-2-carboxylic acid with diphenylmethanamine in dimethylformamide solution. The morpholine ring is in a chair conformation. In the crystal, weak intermolecular C—H⋯O hydrogen bonds link molecules into chains along the b axis.

The title compound, C 24 H 30 N 2 O 4 , was obtained by the reaction of (2R,6S)-4-(tert-butoxycarbonyl)-6-methylmorpholine-2-carboxylic acid with diphenylmethanamine in dimethylformamide solution. The morpholine ring is in a chair conformation. In the crystal, weak intermolecular C-HÁ Á ÁO hydrogen bonds link molecules into chains along the b axis.

Comment
Morpholines are an important class of heterocyclic compounds found in many naturally occurring or synthetically organic molecules (Wijtmans et al., 2004). Especially, the morpholine moiety has found widespread use in medicinal chemistry, and many drugs contain this subunit. For example, antidepressant drug Reboxetine (Hajos et al., 2004;Versiani et al., 2002), Aprepitant in combination with other agents to prevent and control nausea and vomiting caused by chemotherapy (Dando & Perry, 2004;Hale et al., 1998). The morpholine skeleton is also used to construct a number of agrochemical fungicides and bactericides, such as Fenpropimorph and tridemorph (Dieckmann et al., 1993). Furthermore, morpholines have been applied as chiral auxiliaries in asymmetric synthesis (Dave & Sasaki, 2004;Enders et al., 1994). Herewith we report the crystal structure of the title compound (I).
In (I) (Fig. 1), the morpholine ring is in a chair conformation. Weak intermolecular C-H···O hydrogen bonds (Table 1) link the molecules related by translation along axis b into chains.
The mixture was then partitioned between EtOAc and water. The organic layer was then washed successively with saturated aqueous sodium bicarbonate, brine and then dried (MgSO4). The solution was evaporated to dryness in vacuo and the residue purified by flash column chromatography to give the title compound (124 mg) as a colourless solid. Crystals suitable for X-ray structure analysis were obtained by slow evaporation of a solution in EtOAc at room temperature.

Refinement
C-bound H atoms were placed in geometrically idealized positions (C-H = 0.93-0.98 Å) and constrained to ride on their parent atoms with U iso (H) = 1.2-1.5 U eq (C). Atom H2A was located on difference map and isotropically refined. In the absence of any significant anomalous scatterers in the molecule, attempts to confirm the absolute structure by refinement of the Flack parameter in the presence of 1917 sets of Friedel equivalents led to an inconclusive value of 10 (10). Therefore, the Friedel pairs were merged before the final refinement and the absolute configuration was assigned to correspond with that of the known chiral centres in a precursor molecule, which remained unchanged during the synthesis of the title compound.