Abstract

Direct thionation of quinolizidine alkaloids (-)-cytisine, methylcytisine, thermopsine and some of their carbonyl derivatives was realized. It was established that carrying out of the reaction in the boiling toluene with 0.5 eq. of Lawesson’s reagent (LR) is most effective for synthesis of thio analogues of methyl-, allyl-, benzylcytisine and thermopsine. It was found, that formation of thioamides is preferable in the case with starting 3-carboxamides of (-)-cytisine or 2-oxo and 4-oxo derivatives of methylcytisine; and an excess of LR is needed for their exhaustive thionation. It was shown, that thionation of ‘cytisine substituted’ urea and thiourea, as well as Diels-Alder adducts of methylcitisine with phenylmaleimide on basis of this approach was not quite successful: only thionation of the 2-pyridone core has occurred. It should be noted that transformation of urea and thiourea is complicated by side reactions leading to low yields of thio products, and the result of LR interaction with mentioned above diastereomeric Diels-Alder adducts depends on their stereochemistry and thermodynamic stability under reaction conditions.

摘要

实现了喹尼西啶生物碱(-)-金雀花碱、甲基金雀花碱、嗜热霉素及其一些羰基衍生物的直接硫化。确定在沸腾的甲苯中以0.5当量进行反应。Lawesson 试剂 (LR) 对合成甲基、烯丙基、苄基胞嘧啶和嗜热霉素的硫代类似物最有效。已发现，在起始(-)-金雀花碱的3-甲酰胺或甲基金雀花碱的2-氧代和4-氧代衍生物的情况下，优选形成硫代酰胺；并且它们的彻底硫化需要过量的 LR。结果表明，在这种方法的基础上，“金雀花碱取代的”脲和硫脲以及甲基枸橼酸与苯基马来酰亚胺的 Diels-Alder 加合物的硫代作用并不十分成功：仅发生了 2-吡啶酮核的硫代作用。