We report here the synthesis of poly(4-ketovalerolactone) (PKVL) via ring-opening transesterification polymerization (ROTEP) of the monomer 4-ketovalerolactone (KVL, two steps from levulinic acid). The polymerization of KVL proceeds to high equilibrium monomer conversion (up to 96% in the melt) to give the semicrystalline polyketoester PKVL. PKVL displays glass transition temperatures of 7 °C and two melting temperatures at 132 and 148 °C. This polyester can be chemically recycled through hydrolytic degradation. Under aqueous neutral or acidic conditions, the dominating pathway for polyester hydrolysis is through backbiting from the chain end. Under basic conditions, midchain cleavage, accelerated by the ketone carbonyl group in the backbone, promotes the hydrolysis of nearby backbone ester bonds. The final hydrolysis product is 5-hydroxylevulinic acid, the ring-opened hydrolysis product of KVL. PKVL was also observed to degrade under the action of a Brønsted acid to a bis-spirocyclic dilactone natural product altaicadispirolactone, which is a dimer of KVL. This constitutes a rare example of a one-step synthesis of a secondary metabolite of nontrivial structure in which a polymer was the starting material and the sole source of matter. Analogous ROTEP of the isomeric four-membered lactone 4-acetyl-β-propiolactone (APL) was also explored, although this chemistry was not as well-behaved as the KVL to PKVL polymerization.

中文翻译：

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丙戊酸的聚（4-酮戊内酯）：合成及水解降解

我们在这里报告通过单体4-酮戊内酯（KVL，从乙酰丙酸两个步骤）的开环酯交换聚合（ROTEP）合成聚（4-酮戊内酯）（PKVL）。KVL的聚合进行到高平衡单体转化率（在熔体中高达96％），得到半结晶聚酮酯PKVL。PKVL的玻璃化转变温度为7°C，两个熔融温度分别为132和148°C。该聚酯可以通过水解降解进行化学循环。在水性中性或酸性条件下，聚酯水解的主要途径是通过从链端开始的咬合。在碱性条件下，主链中的酮羰基加速中链裂解，促进附近主链酯键的水解。最终的水解产物是5-羟基乙酰丙酸，KVL的开环水解产物。还观察到PKVL在布朗斯台德酸的作用下降解为双螺环双内酯天然产物altaicadispirolactone，它是KVL的二聚体。这是一步合成具有重要结构的次级代谢产物的罕见例子，其中聚合物是起始原料和唯一物质来源。还研究了异构的四元内酯4-乙酰基-β-丙内酯（APL）的相似ROTEP，尽管这种化学反应不如KVL到PKVL聚合那样。这是一步合成具有重要结构的次级代谢产物的罕见例子，其中聚合物是起始原料和唯一物质来源。还研究了异构的四元内酯4-乙酰基-β-丙内酯（APL）的相似ROTEP，尽管这种化学反应不如KVL到PKVL聚合那样。这是一步合成具有重要结构的次级代谢产物的罕见例子，其中聚合物是起始原料和唯一物质来源。还研究了异构的四元内酯4-乙酰基-β-丙内酯（APL）的相似ROTEP，尽管这种化学反应不如KVL到PKVL聚合那样。