Munrolins A–Q (1–17), 17 new ring C-seco limonoids with diverse oxidative patterns of C-12, together with nine known analogues (18–26), were isolated from the CH₂Cl₂ extract of Munronia unifoliolata. The planar structures were elucidated by a combination of 1D and 2D NMR and HR-MS analyses, while the absolute configurations were confirmed by ECD calculations and single-crystal X-ray diffraction. Munrolins A (1) and B (2) were first identified as ring C-seco limonoids with a 12,13-ether bridge moiety. Munrolins C–J (3–10) have a rare reduced primary alcohol fragment, while munrolin Q (17) has an unusual ketal fragment formed by dehydration of C-12/14. These limonoids with diverse alcohol and aldehyde type C11/12 branches may be generated through different degrees of reduction after the Baeyer–Villiger oxidation at the C ring, as key intermediates to supplement the biogenetic pathway of ring C-seco limonoids. Compounds 11, 19, and 26 could reverse the multidrug resistance of MCF-7/doxorubicin cells with reversal fold values of 5.2, 4.5, and 18.3, respectively.

中文翻译：

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具有多种 C-12 氧化模式的柠檬苦素类化合物表明来自 Munronia unifoliolata 的完整环 C-seco 生物遗传途径

Munrolins A-Q（1 - 17），17个新的环C-开环柠檬苦素与C-12的不同氧化图案，具有九个已知类似物（一起18 - 26），从该分离CH ₂氯₂的提取物Munronia unifoliolata。平面结构通过 1D 和 2D NMR 和 HR-MS 分析的组合阐明，而绝对构型通过 ECD 计算和单晶 X 射线衍射证实。Munrolins A ( 1 ) 和 B ( 2 ) 首先被鉴定为具有 12,13-醚桥部分的环 C- seco柠檬苦素。Munrolins C–J ( 3 –10 ) 具有罕见的还原伯醇片段，而 munrolin Q ( 17 ) 具有由 C-12/14 脱水形成的不寻常的缩酮片段。这些具有不同醇和醛型 C11/12 支链的柠檬苦素可能是在 C 环上的 Baeyer-Villiger 氧化后通过不同程度的还原生成的，作为补充环 C- seco柠檬苦素生物遗传途径的关键中间体。化合物11，19，和26能够逆转MCF-7的多药耐药性/多柔比星与逆转细胞分别折叠为5.2，4.5和18.3的值，。