Enantiomers of HA-966 (3-amino-1-hydroxypyrrolid-2-one) exhibit distinct central nervous system effects: (+)-HA-966 is a selective glycine/N-methyl-D-aspartate receptor antagonist, but (-)-HA-966 is a potent gamma-butyrolactone-like sedative.
Singh L, Donald AE, Foster AC, Hutson PH, Iversen LL, Iversen SD, Kemp JA, Leeson PD, Marshall GR, Oles RJ. Proc Natl Acad Sci U S A. 1990 Jan; 87(1):347-51.