Strategy-first synthesis planning for complex natural products
2026-08-07 • Multiagent Systems
Multiagent SystemsArtificial Intelligence
AI summaryⓘ
The authors developed SynthEx, a new computer program that uses advanced language models to plan how to make complex natural molecules. Unlike previous tools that rely on known reactions, SynthEx can suggest inventive and expert-like steps for building molecules with tricky structures. Experts reviewed SynthEx’s plans and found them comparable to human-made strategies, showing the program can truly design realistic chemical syntheses. The authors also created SynthAtlas, a database of these routes, to help researchers work with complex molecules that have no known methods yet.
total synthesisretrosynthetic designnatural productslarge language modelsreaction pathwaysconvergent synthesispolycyclic architecturescatalogue-based synthesis toolscomputer-aided synthesis planningchemical route database
Authors
Daniel Armstrong, Xuan-Vu Nguyen, Octavian Susanu, Gabriel Gibberd, Théo A. Neukomm, Taddäus Strunden, Dan Forster, Morgane Delattre, Shawn Teh, Clément Rols, John Federice, Hayden Leatherwood, M. Lavelle Barnes, Maarten R. Dobbelaere, Peter Wipf, Jon T. Njardarson, Jieping Zhu, Philippe Schwaller
Abstract
The total synthesis of a complex molecule is among the most demanding intellectual and experimental feats in chemistry: a chemist must plan many steps ahead for how to assemble simple building blocks into an intricate target, devise backup strategies, and anticipate procedural challenges. It is also a profoundly creative activity. For half a century, efforts to automate the retrosynthetic design of natural products and other complex molecules have drawn on catalogued reactions, and the resulting tools now report near-complete success on benchmarks built from that same source. But these tools were shaped to fit benchmarked chemistry, and they falter on many natural products, the frontier of the field, whose densely functionalized, polycyclic architectures demand precisely the inventive chemistry the record contains least. Whether a machine could reasonably design such syntheses like an expert chemist does has remained unclear. Here, we show that SynthEx, an agentic framework built on large language models, plans routes to complex natural products that lie beyond the reach of conventional design algorithms. SynthEx proposes competing strategies, assembles a sequence of routine and key steps into a cohesive route, and critiques and improves its own design; the chemistry it favours is more convergent than existing tools produce, and spans a region of reaction space that catalogue-based tools cannot match. Most notably, in blinded assessments, expert chemists judged its key steps comparable to those of published human syntheses and engaged with them as genuine synthesis plans, a response algorithmic route prediction has not previously accomplished. We release routes to more than a thousand natural products as SynthAtlas, an open, interactive database, and anticipate it will become a shared resource for a collection of complex target molecules that lack existing literature routes.