# Microsoft releases RetroChimera model for planning chemical synthesis

_Published Monday, September 21, 2026 at 12:07 PM EDT · AI, Science · Latest · Tier 2 — Notable_

![Microsoft releases RetroChimera model for planning chemical synthesis — Primary](https://www.microsoft.com/en-us/research/wp-content/uploads/2026/09/RetroChimera-TWLIFB-1200x627-1.jpg)

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.

## Sources

- [Microsoft Research](https://www.microsoft.com/en-us/research/blog/improving-synthesis-prediction-of-small-molecules-at-scale-with-retrochimera/)

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Canonical: https://techandbusiness.org/newswire/q5lHARLUBI0WFAehJMBm9Z
Published: 2026-09-21T16:07:57.669Z
Story chronology: 2026-09-21T15:30:19.000Z
Retrieved: 2026-09-21T18:19:51.725Z
Publisher: Tech & Business (techandbusiness.org)