The photooxygenation of the cyclohexadienes 3 and 4, which are readily available through Birch reduction of 2-methylbenzoic acid (1), yielded only one regioisomeric hydroperoxide in a remarkable high diastereoselectivity. A strong directing effect on the stereochemical course of this singlet oxygen ene reaction (Schenck reaction) was observed for various functional groups, including esters and homoallylic alcohols which are unprecedented. This control of diastereoselectivity is rationalized in terms of steric and electronic factors, which provide strong support for perepoxide intermediates in the Schenck reaction. An observation important for synthetic applications is the opportunity to steer the attack of O-1(2) by the proper choice of functional groups. Thus, both diastereomers of the diacetate 11 were selectively prepared from the ester 3a or alcohol 4a of the same starting material 1. The convenience of the reaction sequence Birch reduction-photooxygenation should provide an attractive route to natural products.