We have prepared a new chiral nonracemic reagent (5 (R)-methyl-l-(chloromethyl)-2- pyrrolidinone) in enantiopure form that reacts with alcohols containing a stereogenic center to produce diastereomeric N-(alkoxymethyl)-2-pyrrolidinone derivatives. These derivatives exhibit large and easily observed diastereotopic signals in the proton NMR that allow direct determination of diastereomeric ratio (% dr) for the product.