Irradiation of 2-benzoyladamantane derivatives in zeolites yields the endo-cyclobutanols as the only photoproduct via a γ-hydrogen abstraction process. The cyclobutanols readily undergo retro-aldol reaction to give δ-ketoesters. The enantiomeric excess (ee) in the endo- cyclobutanols is measured by monitoring the ee in the ketoesters. Whereas in solution the ee in the product ketoester is zero, within achiral NaY zeolite, in the presence of a chiral ...