Source of material Propiolicacid(0.21 g, 3mmol) was added to asolution of (5R)-5-phenylmorpholin-2-one (0.53 g, 3m mol) in anhydrous CH 2 Cl 2 (40 mL), and then dicyclohexylcarbodiimide (0.68 g, 3.3 mmol) in anhydrous CH 2 Cl 2 (10 mL) was addedo ver 10 min. The resulting solution was stirred for 12 h. The solid was removed by filtration through ashort pad of Celite and washed with CH 2 Cl 2 (10 mL). The solvent was removed under reduced pressure and the crude material was purified by flash columnchromatography on silica, eluting with PE-EtOAc (3:1) to furnish the title compound as colorlessneedles (1.81 g, yield 84 %; m.p. 125-126°C;[a] D 20 =-50.5, c=1.08, CHCl 3 ). IR, NMR and MS data are available in the CIF file. Experimental detailsAllthe hydrogen atoms were included in calculated positions and treated as riding with. Thea bsolute structure was confirmed with the Flack parameter of 0.016(8). DiscussionThe vast array of available 1,3-dipolar cycloadditions [1,2] providesg eneral andd irecta ccesst of ive-membered heterocycles [3], typically offering high levels of regio-and stereocontrol [4][5][6]. In previous studies, we have reported as eries of enantiomerically pure a-amino acids and enantiopure long-chain threo-2-amino-3-hydroxyesters by diastereo-controlled 1,3-dipolar cycloaddition between azomethine ylid derivatives of (5R)-5-phenylmorpholin-2-one and alkylation chemistry on the 3,4-dehydro derivatives [7][8][9]. Our ongoing interests in azide 1,3-dipolar cycloadditions of this template [10] resulted in the isolation of the title compound. The crystal structure of the title compound is built up of C 13 H 11 NO 3 molecules containing ab enzene and am orpholine ring. The morpholine heterocyclic ring exhibits boat-like conformation. The torsion angles are -12.5(2)°and -16.4(2)°for C9-C10-O1-C7 and C10-C9-N1-C8,respectively, andthe dihedral angle between them is 18.

C 14 H 13 NO 3