In the title compound, C17H19NO5, the cyclo­hexene ring is in a half-chair conformation and the isoxazole ring in an envelope conformation with the N atom as the flap. The C atoms in the 4- and 6-positions are of the same absolute configuration, whereas the C atom in the 5-position is of the opposite configuration, i.e. (4S*,5R*,6S*). The methyl fragment of the eth­oxy­carbonyl group at position 5 is disordered over two sets of sites in a 0.60:0.40 ratio. The crystal packing displays inter­molecular N—H⋯O and O—H⋯O hydrogen bonds.

The title mol­ecule, C21H30N2O5, is chiral with four stereogenic centres. The crystal is a racemate and consists of enanti­omeric pairs with the relative configuration rac-(6S*,7R*,8R*,9S*). The ethyl fragment of the eth­oxy­carbonyl group at position 6 is disordered in a 0.46 (3):0.54 (3) ratio. The crystal structure features inter­molecular N—H⋯O. Intra­molecular O—H⋯N and N—H⋯O hydrogen bonds also occur.

The title compound, [K(C17H18NO5)]n, reveals the relative configuration (4R*,5S*,6R*) whereas its crystals are racemic. The cyclo­hexane ring adopts a half-chair conformation and the isoxazole ring has an envelope conformation. The ethyl fragment of the eth­oxy­carbonyl group at position 5 is disordered in a 0.547 (7):0.453 (7) ratio. The K+ ion is surrounded by five O atoms from three ligands at distances ranging from 2.606 (2) to 3.028 (2) Å, generating a three-dimensional network. The crystal packing displays inter­molecular O—H⋯N and O—H⋯O hydrogen bonds in which the hy­droxy group acts as a double proton donor.

The complete molecule of the title compound, C28H38O2, is generated by a crystallographic centre of symmetry. The molecular conformation displays an intra­molecular C—H⋯π inter­action.

The title compound, C21H29NO6, is chiral with three stereogenic centres. The crystal is a racemate and consists of enanti­omeric pairs with the relative configuration rac-(2R*,3S*,4R*). The ethyl fragment of the eth­oxy­carbonyl group at position 1 is disordered in a 0.60:0.40 ratio. The crystal packing displays inter­molecular O—H⋯O hydrogen bonding. An intra­molecular N—H⋯O hydrogen bond also occurs.