加拿大麦吉尔大学Jean-Philip Lumb研究组的一项最新研究提出利用氧化还原中性的光催化，模拟木脂素生物合成中的氧化自由基环化反应，以实现复杂天然产物的合成。 相关论文发表在2020年12月21日出版的《自然—化学》杂志上。

在该研究中，团队通过氧化还原中性的光催化生成了可能参与了木脂素天然产物生物合成的自由基。研究人员展示了高度氧化的二苯并环辛二烯的全合成，这一类分子的特点是含有来自同一个自由基源的高度融合的多环骨架。进一步研究表明，该生物合成路线中自由基的命运受许多因素控制，这些自由基可以选择参与5元环或11元环的环化，并产生一系列不同的终止反应的事件。该研究为探索这一类天然产物创造了新机会，并为其生物合成来源提供了新思路。

据了解，氧化环化反应可产生许多在生物活性的天然产物中特有的独特化学结构。其中许多反应是由“非经典”或“受阻”的铁加氧酶催化的，并且似乎涉及长寿的自由基。用化学方法模拟这些生物合成路线是合成化学家长久以来的一个目标，但自由基尤其在是氧化条件下的飘忽特性使其难以被驾驭。

附：英文原文

Title: Mimicking oxidative radical cyclizations of lignan biosynthesis using redox-neutral photocatalysis

Author: Zheng Huang, Jean-Philip Lumb

Issue&Volume: 2020-12-21

Abstract: Oxidative cyclizations create many unique chemical structures that are characteristic of biologically active natural products. Many of these reactions are catalysed by ‘non-canonical’ or ‘thwarted’ iron oxygenases and appear to involve long-lived radicals. Mimicking these biosynthetic transformations with chemical equivalents has been a long-standing goal of synthetic chemists but the fleeting nature of radicals, particularly under oxidizing conditions, makes this challenging. Here we use redox-neutral photocatalysis to generate radicals that are likely to be involved in the biosynthesis of lignan natural products. We present the total syntheses of highly oxidized dibenzocyclooctadienes, which feature densely fused, polycyclic frameworks that originate from a common radical progenitor. We show that multiple factors control the fate of the proposed biosynthetic radicals, as they select between 5- or 11-membered ring cyclizations and a number of different terminating events. Our syntheses create new opportunities to explore the medicinal properties of these natural products, while shedding light on their biosynthetic origin.

DOI: 10.1038/s41557-020-00603-z

Source: https://www.nature.com/articles/s41557-020-00603-z