Microsoft ResearchFelix Pultar, John Gardner, Guoqing Liu, Marwin Segler5 min readintermediate
Improving synthesis prediction of small molecules at scale with RetroChimera
Summary
RetroChimera is an open‑source retrosynthesis system that ensembles a Transformer‑based de‑novo model and a GNN template selector with a learned ranking layer. In blind expert evaluations it achieved a 90 % route acceptance rate, far above prior models.
- RetroChimera combines R‑SMILES 2 (Transformer) and NeuralLoc (GNN) using a learned voting scheme to rank predictions.
- The ensemble matches the stronger sub‑model per reaction class, improving recall of rare reaction types.
- Expert chemists accepted 90 % of full routes from RetroChimera versus 20‑50 % for baseline models.
- The code, pretrained weights, and Azure Foundry access are released under an MIT license.
Chemists and ML engineers building synthesis planning pipelines should care because RetroChimera offers higher-quality routes and an open‑source, extensible framework for scaling retrosynthesis.
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