2R,3S -butanedioic acid has two chirality centers: C2 and C3. The IUPAC name for this compound is 2R,3S -2,3-dihydroxybutanedioic acid. The structure of this compound is as follows:HOOC-CH OH -CH OH -COOHTo draw all possible stereoisomers, we need to consider the different configurations at both chirality centers. There are 2^2 = 4 possible stereoisomers:1. 2R,3S -butanedioic acid: HOOC-CH OH -CH OH -COOH2. 2S,3S -butanedioic acid: HOOC-CH OH -CH OH -COOH3. 2R,3R -butanedioic acid: HOOC-CH OH -CH OH -COOH4. 2S,3R -butanedioic acid: HOOC-CH OH -CH OH -COOHThe enantiomer of 2R,3S -butanedioic acid is the molecule with the opposite configuration at both chirality centers. In this case, the enantiomer is 2S,3R -butanedioic acid.