Scientists at Nagoya University have developed an iron-based photocatalyst that reduces reliance on rare metals in organic synthesis. The new design uses fewer costly chiral ligands and enables the first asymmetric total synthesis of (+)-heitziamide A. This advance promotes more sustainable chemical reactions under blue LED light.
Researchers at Nagoya University's Graduate School of Engineering, led by Professor Kazuaki Ishihara, Assistant Professor Shuhei Ohmura, and graduate student Hayato Akao, have introduced a redesigned iron photocatalyst. Published in the Journal of the American Chemical Society in 2026, the study details how this catalyst cuts the use of chiral ligands by two thirds compared to their 2023 version, which required three per iron atom despite only one contributing to enantioselectivity.
The new system incorporates affordable achiral bidentate ligands with chiral ones to form an iron(III) salt structure. This setup enhances catalytic performance and directs the three-dimensional configuration of products. Activated by energy-efficient blue LED light, it facilitates a controlled radical cation (4 + 2) cyclization, forming six-membered rings with 1,2,3,5-substituted adducts common in natural products.
Using this catalyst, the team achieved the first total asymmetric synthesis of (+)-heitziamide A, a compound from medicinal plants that suppresses respiratory bursts. Prior syntheses had not produced the natural enantiomer asymmetrically. The mirror-image catalyst could similarly yield (-)-heitziamide A.
"The new catalyst design represents the definitive form of chiral iron(III) photoredox catalysts," Ohmura stated. "We believe this achievement marks a significant milestone in advancing iron-based photocatalysis."
Ishihara added, "Achieving the first-ever asymmetric total synthesis of (+)-heitziamide A using this catalytic reaction is a remarkable accomplishment." The approach allows construction of complex molecules, including pharmaceutical precursors, with abundant iron instead of scarce metals like ruthenium and iridium.
This development suggests potential for enantioselective synthesis of additional bioactive substances via the same cycloaddition step.
