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Methods for making monodisperse polyester copolymers of predetermined length, com‐position, and sequence are reported. Alternating oligomers of (L)‐lactic‐co‐glycolic acid (La‐co‐Gl), isosteric with polypeptides, are prepared by solution methods of protecting, coupling, and deprotecting alcohol and acid groups. The carboxylic acid is protected by benzyl ester formation and released by hydrogenation. The hydroxyl group is protected as the methoxyethoxyethyl ether and deprotected with sodium iodide and trimethylsilyl chlo‐ride. Coupling uses dicyclohexylcarbodiimide. End‐capped alternating oligomers containing (GILa)4 and (GILa)8 show polymer properties. They are noncrystalline oils that exhibit discernable Tg. The conformation of GILa and LaGl diads in the polyesters is shown to be similar to isosteric peptide diads GlyAla and AlaGly. Exactly structured, monodisperse polyesters suggest a chemical parallel to proteins. Designed struc‐tural templates combining sheet‐form (Gl)n and helical (La)n segments are at‐tractive synthesis targets. The solution preparations reported here can be applied, but it is suggested that biosynthetic methods for introducing single ester units into peptide chains be adapted to synthesize precisely fashioned polyesters. © 1995 John Wiley & Sons, Inc.

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and a stirrer, were added 24.1 g. (0.122 mole) of diethyl a,adimethylglutarate (VIII), 10 ml. of water, and 200 ml. of methyl alcohol. A solution of 4.5 g. (0.08 mole) of potassium hydroxide in 15 ml. of water was then added at a rate sufficient to keep the reaction mixture below 26°over a period of 6 hr. The mixture was then stirred at room temperature for an additional 10 hr. After the major portion of the methyl alcohol was removed by distillation under reduced pressure, 300 ml. of water was added and the residue was acidified to pH 4 by the dropwise addition of concentrated hydrochloric acid. The aqueous solution was then extracted with four 100-ml. portions of ether. After the ether extracts had been dried over anhydrous magnesium sulfate, the mixture was fractionated through a 2-ft. spiral-wire column to yield 13.7 g. (65%) of 4-methyi-4-carbethoxypentanoic acid (VIII), b.p. 100°( 0.4 mm.), n26o 1.4355.

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