Abstract Birch bark tar, an organic material frequently encountered during archaeological excavations, has been identified from its lipid composition on the cracks of a ceramic dated to the late Neolithic. Lipids of this black substance were dominated by a characteristic triterpenoid assemblage of lupane-related triterpenoids from birch bark, together with their thermal degradation products formed during preparation of the tar. Among the latter, four main series of unusual triterpenoid esters have been detected and were postulated to correspond to esters of Δ 2-betulin and Δ2-dihydrobetulin based on their mass spectra and hydrolysis experiments. Their conclusive identification has been achieved by synthesis of reference compounds. These compounds most likely originate from the esterification between triterpenoid alcohols related to betulin and fatty acids from suberin formed upon heating of birch bark tar. They could be considered as markers of intense heating during birch bark tar preparation using the “single pot” procedure.

中文翻译：

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桦树皮焦油中桦木脑相关酯的鉴定、起源和考古意义

摘要 桦树皮焦油是考古发掘过程中经常遇到的一种有机材料，已从新石器时代晚期陶瓷裂缝上的脂质成分中鉴定出来。这种黑色物质的脂质主要由桦树皮中与羽扇豆相关的三萜类化合物的特征性三萜类组合物以及在焦油制备过程中形成的热降解产物组成。在后者中，已检测到四个主要系列的不寻常的三萜酯，并根据它们的质谱和水解实验推测它们对应于 Δ2-桦木脑和 Δ2-二氢桦木脑的酯。它们的最终鉴定已通过参考化合物的合成获得。这些化合物最有可能来源于桦木皮焦油加热形成的与桦木脑相关的三萜醇和来自木栓质的脂肪酸之间的酯化反应。在使用“单锅”程序制备桦树皮焦油期间，它们可以被视为强烈加热的标志。