Abstract The total syntheses of (+)-polygalolide A and (+)-polygalolide B have been completed by using a carbonyl ylide cycloaddition strategy. Three of the four stereocenters, including two consecutive tetrasubstituted carbon atoms at C2 and C8, were incorporated through internal asymmetric induction from the stereocenter at C7 by a [Rh 2 (OAc) 4]- catalyzed carbonyl ylide formation/intramolecular 1, 3-dipolar cycloaddition sequence. ...