A convenient new route to enantiopure 3-hydroxy-5-oxo esters and 5,6-dihydropyran-2-ones: intricacies of the trithioorthoester protecting group

3-Hydroxy-5-oxo esters are useful precursors to biologically active compounds. An expedient three-step synthesis of 3-hydroxy-5-oxo esters based on dithiane anion chemistry is presented along with the transformation of the 3-hydroxy-5-oxo esters into 5,6-dihydropyran-2-ones.