Complex sentence: Chiral Lewis acids (CLAs) are a class of Lewis acid catalyst used in enantioselective asymmetric synthesis reactions which produce optically active products from optically inactive or impure starting materials.
Split into simpler sentences: Chiral Lewis acids (CLAs) are a type of Lewis acid catalyst that effects the chirality of the substrate as it reacts with it. Since they affect chirality, they produce optically active products from optically inactive or mixed starting materials.