Polymer-supported chiral Lewis acids were prepared from bromoboranes and crosslinked polymers having chiral amino alcohol or diol moieties. These polymers were used as chiral catalysts for Diels-Alder reactions of cyclopentadiene with methacrolein to give optically active cycloadduct in high chemical yield with high exo selectivity. Optical yield up to 54% ee was obtained by the use of polymeric chiral catalyst derived from (S)-proline. The potential of this type of approach in asymmetric synthesis is discussed.