The title compounds, C₁₂H₁₃NO₄, are derived from L-threonine and DL-threonine, respectively. Hydrogen bonding in the chiral derivative, (2S/3R)-3-hydroxy-2-(1-oxoisoindolin-2-yl)butanoic acid, consists of O-Hacid...Oalkyl-H...O=Cindole chains [O...O 2.659 (3) and 2.718 (3) Å], Csp³-H...O and three C-H...πarene interactions. In the (2R,3S/2S,3R) racemate, conventional carboxylic acid hydrogen bonding as cyclical (O-H...O=C)₂ [graph set R₂²(8)] is present, with Oalkyl-H...O=Cindole, Csp³-H...O and C-H...πarene interactions. The COOH group geometry differs between the two forms, with C-O, C=O, C-C-O and C-C=O bond lengths and angles of 1.322 (3) and 1.193 (3) Å, and 109.7 (2) and 125.4 (3)°, respectively, in the chiral structure, and 1.2961 (17) and 1.2210 (18) Å, and 113.29 (12) and 122.63 (13)°, respectively, in the racemate structure. The O-C=O angles of 124.9 (3) and 124.05 (14)° are similar. The differences arise from the contrasting COOH hydrogen-bonding environments in the two structures.