diols to aminohydroxy acids by oxidation of the primary hydroxy group mediated by homogeneous and heterogeneousTEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl radical) is reported. The synthesis uses NaOCl as primary oxidant and TEMPO, either dissolved in the homogeneous phase or entrapped in a sol-gel matrix, as catalytic mediator. HomogeneousTEMPO is suitable for the oxidation of aliphatic methylamino