A rapid and convenient synthesis of β-proline

A short, reliable, and cheap synthesis of both enantiomers of β-proline, an efficient organocatalyst and an important building block in medicinal chemistry, has been developed in four steps (overall yield: 72%) from the diasteromeric adducts of methyl itaconate and (R)-α-methylbenzylamine. The key step involves the chemoselective reduction of a lactam group in the presence of a benzyl ester.