Blind review finds AI synthesis routes match human chemistry

An AI chemistry agent called SynthEx designed synthesis routes that blinded expert chemists rated comparable to published human chemistry, per a new paper on arXiv.

That matters because retrosynthesis software struggles hardest with this kind of target: complex natural products whose polycyclic structures demand inventive chemistry reaction databases barely cover. SynthEx went after that gap directly, and its key steps read to experts as genuine strategic choices, not just chained-together reactions.

The agent doesn't stop at proposing one path. It generates competing synthetic strategies, then assembles routine and key steps into one cohesive route. It critiques and revises that route before presenting it. That's the exact gap other retrosynthesis tools miss, since they lean on a reaction catalogue that's thin on this kind of inventive chemistry.

The team released routes for more than 1,000 natural products as SynthAtlas, an open database, alongside the paper.

What's still unproven

Expert review is judgment, not a lab bench. The paper describes chemists rating routes as plausible and comparable to published work. It doesn't describe anyone actually running the 1,000-plus routes in SynthAtlas to see if they make the target molecule. That gap matters for anyone deciding whether SynthAtlas is a starting point or a finished answer.

If a meaningful share of SynthAtlas's routes survive real synthesis attempts, that's the tell. The reaction-database bottleneck that's limited retrosynthesis software for years turns out to be a data problem an agent can route around, not a chemistry problem. Worth watching whether anyone outside the paper's authors tries to run one of these routes at the bench.