A total synthesis of the marine natural product leucascandrolide A has been completed. The titaniumtetrabromide-mediated Mukaiyama aldol−Prins (MAP) reaction with aldehydes developed in our groupprovided a highly convergent and stereoselective method for assembling the core of the molecule. Anew class of MAP reactions with acetals is introduced, and mechanistic considerations for both MAPmethods are described. The total synthesis was completed by coupling of the side chain through twoavenues: a known Still−Gennari olefination and a new Z-selective aldol/dehydroselenation reaction.Both procedures were highly selective and provided the natural product.