AbstractFully enolized N‐hydroxypyridine‐2,4‐diones with a 3‐enoyl or 3‐dienoyl or 3‐trienoyl substituent (collectively named “3‐polyenoyl substituent“ hereafter) define the core of a number of δ‐lactam natural products. We developed a strategy for establishing such motifs in a convergent and stereoselective manner. The polyenoyl moiety of our target molecules stemmed from simply, two‐fold or three‐fold unsaturated and almost completely enolized ω‐bromo‐β‐ketothioesters, two of which were obtained for the first time. The N‐bound hydroxy group of our target structures originated from an O‐(2,4,6‐trimethoxybenzyl)‐protected β‐(hydroxylamino)propionic ester, first obtained in this study, too. The mentioned building blocks were combined intermolecularly by a thioester hydroxylaminolysis and thereafter intramolecularly by a Williams‐type Dieckmann cyclization. The resulting N‐(2,4,6‐trimethoxybenzyloxy)dihydropyridine‐2,4‐diones were oxidized with CBrCl3 and DBU. The N‐(2,4,6‐trimethoxybenzyloxy)pyridine‐2,4‐diones gained thereby were debenzylated – jointly with their (4‐methoxybenzyl) aryl ether moiety – with F3CCO2H. This liberated the target structures.
摘要具有 3-烯酰基、3-二烯酰基或 3-三烯酰基取代基(以下统称为 "3-聚烯酰基取代基")的完全烯醇化 N-羟基吡啶-2,4-二酮定义了许多 δ-内酰胺天然产物的核心。我们开发了一种以趋同和立体选择性方式建立此类基团的策略。我们的目标分子中的聚烯酰基来自于简单、两倍或三倍不饱和且几乎完全烯醇化的ω-溴-β-硫酮酯,其中有两种是首次获得的。我们的目标结构的 N 键羟基来自 O-(2,4,6-三甲氧基苄基)保护的 β-(羟基氨基)丙酸酯,这也是本研究首次获得。上述结构单元通过硫代酯类羟基氨基化反应在分子间结合,然后通过威廉姆斯式迪克曼环化反应在分子内结合。生成的 N-(2,4,6-三甲氧基苄氧基)二氢吡啶-2,4-二酮被 CBrCl3 和 DBU 氧化。由此得到的 N-(2,4,6-三甲氧基苄氧基)吡啶-2,4-二酮与它们的(4-甲氧基苄基)芳基醚分子一起用 F3CCO2H 进行脱苄基反应。这样就得到了目标结构。