立体中心
绝对构型
立体化学
非对映体
对映体
部分
化学
缩醛
圆二色性
不对称碳
异构化
生物合成
对映选择合成
有机化学
光学活性
酶
催化作用
作者
Ryuhi Kanehara,Yuki Oinuma,Hayato Maeda,Masanori Okazaki,Katsuhiro Konno,Kazuaki Tanaka,Minoru Hashimoto
标识
DOI:10.1021/acs.jnatprod.3c00373
摘要
Paraphaeolactones A1, A2, B1, and B2 (1–4, respectively), known arthropsadiol D (5), massariphenone (6) and its positional isomer 7, and massarilactones E (8) and G (9) were isolated from the culture broth of Paraphaeosphaeria sp. KT4192. Although the structural resemblance between 1 and 2 implies that these comprised a diastereomeric pair at the C-2 stereogenic center, electronic circular dichroism (ECD) spectral analyses revealed that they were pseudo-enantiomers possessing the common (2R)-configuration. Paraphaeolactones B1 and B2 (3 and 4) were the derivatives of 2, which equipped the 3-(1-hydroxy-2-oxopropyl)-4-methylcatechol moiety via an acetal bond at C-10. The relative configurations of their acetal carbons were elucidated by NOE experiments, and those of C-8′ were deduced independently by ECD spectral analysis. The present study disclosed that 1–5, 8, and 9 contain a methylcyclohexene substructure with the same absolute configuration. This prompted us to reinvestigate the absolute configurations of known structurally related fungal metabolites, allowing us to conclude that the methylcyclohexene moieties of these natural products have the same absolute configuration despite the variety of configurations of other stereogenic centers. The plausible biosynthetic routes for 1–9 are discussed on the basis of the above conclusion. We propose a Favorskii rearrangement as the key transformation for biosyntheses of 1–4.
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