Xylarins A–D, Two Pairs of Diastereoisomeric Isoindoline Alkaloids from the Endolichenic Fungus <i>Xylaria</i> sp.
Ke Xu, Ruijuan Li, Rongxiu Zhu, Xiaobin Li, Yuliang Xu, Qiaobian He, Fei Xie, Yanan Qiao, Xiaoyi Luan, Hong‐Xiang Lou
Abstract
Two pairs of diastereoisomeric isoindoline alkaloids, xylarins A–D (1–4), were isolated from the endolichenic fungus Xylaria sp. Xylarins A and B (1 and 2) possess a previously undescribed 5/6/5–5/6 polycyclic scaffold, featuring a combination of a novel dihydrobenzofurone unit and an isoindoline unit, while xylarins C and D (3 and 4) contain an additional N,N-dimethylaniline at the C-3′ position. Their structures were elucidated by comprehensive spectroscopic analyses combined with single-crystal X-ray diffraction and electronic circular dichroism calculations. The plausible biosynthetic pathways and gene clusters for 1–4 were proposed. Compound 1 exhibited significant antithrombotic activity.