A chiral N-crotonyloxazolidinone Diels-Alder adduct.

(4S)-4-Benzyl-3-[(4S,5S)-(1-methoxy-5-methylcyclohexen-4- yl)carbonyl]-2-oxazolidinone, C19H23NO4, M(r) = 329.40, monoclinic, P2(1), a = 11.453 (3), b = 7.163 (4), c = 11.929 (2) A, beta = 111.86 (2) degree, V = 908.3 (5) A3, Z = 2, D chi = 1.20 g cm-3, lambda (Mo K alpha) = 0.71073 A, mu = 0.79 cm-1, F(000) = 352, T = 297 K, R = 0.034 for 885 reflections with Fo2 greater than 0. The molecule is extended in the crystal; there is a small twist, -13.1 (2) degree, about the amide-like C--N bond joining the oxazolidinone ring to the carbonyl group. The configurations at the two optical centers in the cyclohexene ring confirm the anticipated stereospecificity of the Diels-Alder cycloaddition synthesis.