(1S, 2R, 2′S, 3′aS,5R)-2′-[(1R)-1-hydroxyethyl]-2-isopropyl-5,5′-dimethyl-3′,3′a-dihydro-2′H-spiro[cyclohexane-1,6′-imidazo[1,5-b]isoxazol]4′(5′H)-one

Cycloaddition of a (-)-menthone-derived nitrone to racemic but-3-en-2-ol led to two spirobicyclic heterocycles, with opposite configurations at the C atom attached to the OH group. This paper describes the S epimer of the 1-hydroxyethyl substituent in imidazoisoxazole C17H30N2O3, (I). The R epimer, (II), is presented in the previous article [Aouadi, Jeanneau & Praly (2007), Acta Cryst. E67, o1324 - o1326]. The absolute configurations of both epimers were assigned from the known configuration of the starting (-)-menthone derived nitrone. In (I), there is an O- H (. . .) O hydrogen bond (O-H O-. . . = 1.96 angstrom and O - H (. . .) O = 165 degrees) that concatenates the molecules along the b axis. In addition, there are C-H (. . .) O and C-H (. . .) N hydrogen bonds.