Researchers have developed a method for synthesizing a ‘pure’ alternating copolymer of L– and D-lactic acids in which L– and D-lactic acids are alternately arranged, i.e., a ‘syndiotactic’ poly(lactic acid). With this method, it is possible to synthesize syndiotactic polyesters in which L- and D-type monomers are arranged alternately. These polyesters are conventionally difficult to synthesize. The present method is expected to facilitate the development of novel polyesters with unprecedented characteristics.