Ab-initio investigation of unexpected aspects of hydroxylation of diketopiperazines by reaction with dioxiranes

In an explorative study of the opportunities for synthesis provided by oxidation of natural aminoacidic compound with methyl-(trifluoromethyl)dioxirane, we noticed that oxidation of the cyclic compound, when successful, leads to the ?-hydroxy compound, notwithstanding the presence of the isopropyl groups that are usually easy targets for this reaction, as verified with the homologous acyclic compound. We therefore initiated an ab-initio study of the reactions aimed at determining the role of the ring and explaining the reactivity differences of the cis and trans configurations. Consistently with recent literature, we confirm the fundamental role of an adduct configuration in which the dioxirane O-O bond is largely divaricated and electron pairing is broken, often denoted in the literature as diradicaloid.