Complex sentence: Since thalidomide has a stereogenic carbon atom, it exists as two enantiomers and tests with mice in 1961 suggested that only one enantiomer was teratogenic while the other possessed the therapeutic activity.
Split into simpler sentences: Since thalidomide has a stereogenic carbon atom, it exists as two enantiomers. Tests with mice in 1961 suggested that only one enantiomer was teratogenic while the other possessed the therapeutic activity.