Practical synthesis of diastereoisomers by a temperature-guided reversal of diastereoselectivity in the desymmetrization of meso-bridged anhydrides with a chiral oxazolidin-2-one

A perfect temperature-guided diastereoselectivity switch was observed in the desymmetrization of some meso-bridged tricyclic succinic anhydrides with a lithiated chiral 5,5-disubstituted oxazolidin-2-one called SuperQuat. Experimental conditions required for the optimum diastereoselectivity and to obtain the individual diastereoisomers of the SuperQuat linked meso-anhydride opening products with acceptable purity and yield have been established.