Synthesis of stereoregular poly[(2S,3S)-benzyl β-3-methylmalate]

The asymmetric lactone (3 S, 4 R)-3-methyl-4-benzyloxycarbonyl-2-oxetanone ( 6 ) was anionically polymerized to give an insoluble, crystalline, highly isotactic polymer with (2 S, 3 S)-benzyl β-3-methylmalate repeating units. Solubility was achieved by copolymerization of 6 with the recemic (R, S)-butyl malolactonate ( 7 ). The semicrystalline copolymer was characterized (M̄_n = 107 000, T_g = 29,6°C, T_m = 161°C, [α] = 1,5 deg · dm⁻¹ · g⁻¹ · cm³) and its stereosequence investigated by ¹³C NMR.