By taking advantage of the appreciable stability of dioxiranes in water, a safe yet efficient route to omega-nitro acids by oxidation of lactams of various ring sizes under mild conditions has been reported. In essentially all the cases examined, reactions proceed selectively to afford products in remarkably high yields (up to 99%) and with high purity (94-99%). Also, an interesting example of higher reaction selectivity in water than in organic solvent (acetonitrile) is discussed. (C) 2012 Elsevier Ltd. All rights reserved.