The (3S)-[(benzyloxycarbonyl)ethyl]-1,4-dioxan-2,5-dione (BED) was prepared in four steps starting from glutamic acid and bromoacetyl bromide. According to X-ray diffraction analysis, the pendant functional group is located in equatorial position and points away from the six-membered ring. The organo-catalyzed ring-opening polymerization of BED was promoted with 4-dimethylaminopyridine (DMAP) and the combination of thiourea TU^Cy and (−)-sparteine. PolyBED samples of number-average molar mass M_n up to 36000 and narrow polydispersity (M_w/M_n < 1.25) were thereby prepared in a controlled manner under mild conditions (dichloromethane solution, 30 °C), as substantiated by size-exclusion chromatography, matrix-assisted laser desorption ionization time-of-flight−mass spectrometry (MALDI-TOF-MS) and nuclear magnetic resonance (NMR) spectroscopy. The pendant functional group does not interfere with the polymerization and BED was even found to be slightly more reactive than lactide. Despite the strongly dissymmetric substitution pattern of the 1,4-dioxan-2,5-dione core, the ensuing polyBED polymers present a random distribution of glycolic-[(benzyloxycarbonyl)ethyl]glycolic (gly glu) units, as supported by a ¹H−¹³C HMBC 2D NMR experiment. The preparation of 1:1 adducts with n-pentanol confirmed that ring-opening of BED occurs almost indifferently on either of the endocyclic ester groups. Poly(α-hydroxyacids) featuring pendant carboxylic acids were finally obtained by acetylation of the terminal OH groups followed by hydrogenolysis.

中文翻译：

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谷氨酸衍生的1,4-二恶烷-2,5-二酮的有机催化开环聚合

（3S）-[（（苄氧羰基）乙基] -1,4-二恶烷-2,5-二酮（BED）从谷氨酸和溴乙酰溴开始分四个步骤制备。根据X射线衍射分析，侧基官能团位于赤道位置并且指向远离六元环的位置。BED的有机催化开环聚合反应通过4-二甲基氨基吡啶（DMAP）以及硫脲TU ^Cy和（-）-天冬氨酸的组合来促进。数均摩尔质量M _n高达36000且多分散性窄（M _w / M _n从而在温和条件下（二氯甲烷溶液，30°C）以受控方式制备了<1.25），如尺寸排阻色谱法，基质辅助激光解吸电离飞行时间质谱法（MALDI-TOF-MS）所证实）和核磁共振（NMR）光谱。侧基官能团不干扰聚合，甚至发现BED的反应性比丙交酯略高。尽管1,4-二恶烷-2,5-二酮核的取代基存在强烈的不对称分布，但随后的polyBED聚合物表现出乙醇酸-[（苄氧羰基）乙基]乙醇酸（gly glu）单元的无规分布，如^1所示。 H- ¹³ C HMBC 2D NMR实验。n为1：1的加合物的制备-戊醇证实，在任何一个内环酯基团上，BED的开环几乎都无关紧要。最终，通过末端OH基团的乙酰化，然后进行氢解，获得了侧链羧酸为特征的聚（α-羟酸）。