Abstract: The 2-oxetanone (beta.lactone) ring is present in several natural biologically active compounds. The use of chiral (eta6) tricarbonylchromium derivatives for the stereoselective synthesis of small ring heterocycles is already well documented.1-4 Among the different methods for preparing b-lactons, we envisage the lactonization "via" b-hydroxy carboxylic acids as promising approch to this class of compounds starting from optically pure substituted chromium tricarbonyl benzaldehydes. Following the procedure reported in the scheme, a series of enantiomerically pure b-lactones have been obtained. One example is reported in this Poster.