A highly enantioselective anti-diastereoselective hetero-Diets-Alder reaction between a glyoxylate and siloxy- or methoxydienes using a chiral phosphoric acid catalyst that possesses less bulky phenyl groups at the 3 and 3' positions of binaphthyl has been developed. The diastereoselectivities presented are disparate to those previously reported for hetero-Diets-Alder reactions catalyzed by a chiral Lewis acid.