近日，上海交通大学教授瞿旭东团队研究了酶促双氧Diels-Alder反应构建(-)-蒽苯并氧杂辛酮的氧桥三环缩醛单元。该项研究成果发表在2025年4月22日出版的《自然-化学》杂志上。

杂Diels-Alder（HDA）反应是合成天然产物和生物活性化合物中六元杂环的关键方法。尽管它在合成化学中很重要，但天然发生的酶促HDA反应很少见，并且仅限于单个杂原子。研究组报告了Abx_（−）F，这是一种双功能邻位氧螯合物（VOC）样蛋白质，可以催化脱水和双oxa-Diels-Alder反应，立体选择性地形成（-）-蒽苯并氧杂辛酮（（−）-ABX）的氧桥三环缩醛。

同位素分析和密度泛函理论计算揭示了脱水协调、协同的HDA机制。Abx_（−）F的晶体结构和Abx_（-）F与其底物类似物和（-）-ABX的NMR复合物结构定义了反应的结构基础。突变分析确定Asp17是介导脱水的通用碱基，形成立体选择性双oxa-HDA的邻醌甲基化中间体。这项工作建立了多杂原子Diels-Alderase的分子和结构基础，为设计多杂原子DA酶工具铺平了道路。

附：英文原文

Title: An enzymatic dual-oxa Diels–Alder reaction constructs the oxygen-bridged tricyclic acetal unit of (–)-anthrabenzoxocinone

Author: Yan, Xiaoli, Jia, Xinying, Luo, Zhenyao, Ji, Shunjia, Zhang, Meng-Jie, Zhang, Hui, Yu, Mingjia, Orts, Julien, Jiang, Kai, Lin, Zhi, Deng, Zixin, Kong, Xu-Dong, Kobe, Bostjan, Zhao, Yi-Lei, Mobli, Mehdi, Qu, Xudong

Issue&Volume: 2025-04-22

Abstract: The hetero-Diels–Alder (HDA) reaction is a key method for synthesizing six-membered heterocyclic rings in natural products and bioactive compounds. Despite its importance in synthetic chemistry, naturally occurring enzymatic HDA reactions are rare and limited to a single heteroatom. Here we report Abx()F, a bifunctional vicinal oxygen chelate (VOC)-like protein that catalyses dehydration and dual-oxa Diels–Alder reactions to stereoselectively form the oxygen-bridged tricyclic acetal of (–)-anthrabenzoxocinone (()-ABX). Isotope assays and density functional theory calculations reveal a dehydration-coordinated, concerted HDA mechanism. The crystal structure of Abx()F and NMR complex structures of Abx()F with its substrate analogue and ()-ABX define the reaction’s structural basis. Mutational analysis identifies Asp17 as a general base that mediates dehydration, forming an o-quinone methide intermediate for stereoselective dual-oxa HDA. This work establishes the molecular and structural basis of a polyheteroatomic Diels–Alderase, paving the way for designing polyheteroatomic DA enzymatic tools.

DOI: 10.1038/s41557-025-01804-0

Source: https://www.nature.com/articles/s41557-025-01804-0