Microsoft releases RetroChimera model for planning chemical synthesis

Microsoft Research released RetroChimera's implementation and model weights under an MIT license, making the system available through GitHub and Microsoft Foundry. The model plans how to make a target molecule by ranking routes backward from that molecule to simpler starting materials. RetroChimera combines a transformer that can generate unfamiliar reaction patterns with a graph model constrained by templates extracted from training data. A learned voting system merges their ranked proposals. Microsoft says PhD-level chemists in blind tests preferred its individual reaction predictions over those from earlier models and recorded literature reactions, but the company also notes that unconstrained generation can hallucinate.