Diastereoselective synthesis of hydantoin- and isoxazoline-substituted dispirocyclobutanoids.

Synthetic strategies for constructing novel achiral cyclobutanoid isoxazolidinoimidazolidinedione heterocycles, with a generalized structure of II, have been developed via 1,3-dipolar cycloaddition and carbanilide cyclization transformations from methylenecyclobutane 13. The exo methylene cyclobutane system has made the realization of some diasteroselectivity possible, such that the H-bond (Boc-NH) directed product (i.e., 14) was obtained with 3:1 selectivity relative to the non-H-bond directed product (i.e., 15).