Photoinduced hydrogen transfer and electron transfer to excited states of carbonyl compounds are two of the most intensively investigated fundamental processes in photochemistry. [1][2][3] Numerous studies have been performed to elucidate the mechanisms as well as to determine ways to control these processes, and have involved variation of the electronic nature of the excited state (n,p* versus p,p*) [4,5] and its multiplicity, that is, singlet-versus triplet-state photochemistry. [6,7] Electronic donor properties, such as bond dissociation energies and ionization potentials, [1,4,7,8] structural features, namely, stereoelectronic and steric hindrance effects, [9,10] and the influence of the chemical surrounding (solvent polarity, hydrogen bonding) have also been investigated. [11][12][13][14] However, relatively little is known about diastereomeric differentiation in the intramolecular quenching of excited states, which is basically related to the search for asymmetric photoreactions, and is another phenomenon which could control the kinetics of hydrogen-or electron-transfer processes. [15][16][17] Recently, studies were performed on the intramolecular exciplex-mediated quenching of triplet states in diastereomeric dyads consisting of 2-arylpropionic acid derivatives and electron donors of biological importance, namely, tyrosine and tryptophan. [18,19] Other studies focused on the chiral control of intramolecular charge-transfer quenching of ketone triplets in solution and in the solid state. [20,21] Reports on related intermolecular quenching are rather scarce and are also focused mainly on exciplexmediated processes. [22,23] Although the possibility of conformational control of photoinduced hydrogen abstractions in Norrish type II reac-