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AI retrosynthesis in seconds

Describe the molecule you want to make. Rasyn generates the optimal route, guides execution, analyzes results, and learns from every experiment. Turning months of work into days.

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Sessions

Synthesis Sessions

Plan retrosynthesis, generate protocols, and source reagents

New Session
New Synthesis Session
Enter SMILES notation — e.g. CC(=O)Oc1ccccc1C(=O)O
RetroTransformer v2
Try:
Search sessions...
All Status
Retrosynthesis of Theophyllinecompleted
Cn1c2c(c(=O)n(c1=O)C)[nH]cn22 hours ago
4 routes
Retro: CCOC(c)cc(c)OCC(=O)Ocompleted
CCOC(c)cc(c)OCC(=O)O2 hours ago
3 routes
Retrosynthesis of Ibuprofencompleted
CC(C)Cc1ccc(cc1)C(C)C(=O)O3 hours ago
5 routes
Retro: DCC(=O)Oc1cccK(=O)=Orunning
DCC(=O)Oc1cccK(=O)=Oabout 3 hours ago
Retrosynthesis of Paracetamolcompleted
CC(=O)Nc1ccc(O)cc14 hours ago
3 routes
Aspirin Retrosynthesiscompleted
CC(=O)Oc1ccccc1C(=O)O5 hours ago
4 routes
Retrosynthesis of Caffeinecompleted
CN1C=NC2=C1C(=O)N(C(=O)N2C)C6 hours ago
6 routes

Used by research chemists & scientists at

Yale UniversityCaltechUniversidad Autónoma de ZacatecasAragen Life SciencesHexaSynth TechnologiesIFM Therapeutics1200 PharmaAin Shams UniversityBursa Technical UniversitySphaera PharmaUniversity of OxfordPiramal GroupUniversidad de Costa RicaJubilant BiosysUniversitas Jenderal SoedirmanUniversidade de LisboaUSTCKAISTYale UniversityCaltechUniversidad Autónoma de ZacatecasAragen Life SciencesHexaSynth TechnologiesIFM Therapeutics1200 PharmaAin Shams UniversityBursa Technical UniversitySphaera PharmaUniversity of OxfordPiramal GroupUniversidad de Costa RicaJubilant BiosysUniversitas Jenderal SoedirmanUniversidade de LisboaUSTCKAISTYale UniversityCaltechUniversidad Autónoma de ZacatecasAragen Life SciencesHexaSynth TechnologiesIFM Therapeutics1200 PharmaAin Shams UniversityBursa Technical UniversitySphaera PharmaUniversity of OxfordPiramal GroupUniversidad de Costa RicaJubilant BiosysUniversitas Jenderal SoedirmanUniversidade de LisboaUSTCKAISTYale UniversityCaltechUniversidad Autónoma de ZacatecasAragen Life SciencesHexaSynth TechnologiesIFM Therapeutics1200 PharmaAin Shams UniversityBursa Technical UniversitySphaera PharmaUniversity of OxfordPiramal GroupUniversidad de Costa RicaJubilant BiosysUniversitas Jenderal SoedirmanUniversidade de LisboaUSTCKAIST

Smarter tools,
faster synthesis.

Rasyn / Search
Enter SMILES, name, or draw…⌘K
SMILES
CC(=O)Oc1ccccc1C(=O)O
AspirinC₉H₈O₄MW · 180.16
2D StructureRDKit · canonical

Research with precision

Enter a SMILES string, draw a structure, or search by name. Rasyn identifies the molecule and prepares it for retrosynthetic analysis instantly.

Retrosynthesis
Route 1/5 routes
94.2%
3 stepsLow hazard$42
Aspirin
Salicylic acid
+
Ac₂O
H₃PO₄
85 °C · 15 min
Step 1 · Protocol

Dissolve 2.0 g salicylic acid in 5 mL acetic anhydride.

Add 5 drops H₃PO₄. Heat at 85 °C for 15 min…

AI plans the synthesis

Our hybrid model ensemble (RetroTransformer v2 + LLM v6) produces ranked multi-step routes with step-by-step protocols, scored by confidence, safety, and cost.

Reagent Sourcing
Vendors4 found · sorted by stock
Sigma-Aldrich
A5376-100G$28.50
In Stock
Fisher Scientific
AC158180250$31.00
In Stock
TCI America
A0097$22.00
2-3 days
Alfa Aesar
A15716$26.80
In Stock
All reagents sourced
3 of 3 starting materials available

Source every reagent automatically

PubChem-powered vendor search finds every starting material with stock status across Sigma-Aldrich, Fisher, TCI, and more. One click to purchase.

Agent

One agent.
500+ chemistry tools.

Ask in plain English. Rasyn picks the right tools, runs them in sequence, and returns a complete plan with citations — retrosynthesis, protocol generation, vendor sourcing, and safety checks, all from one prompt.

See how it works
Rasyn / Agent
Paracetamol synthesis·session #1284
RetroTransformer v2 · LLM v6Live
Ask Rasyn anything / it picks the right tools.

Features

Built for
real chemistry.

Model Ensemble
RetroTransformer v269.7% top-1
94.2%
87.1%
72.4%
RSGPT v6 LLM61.7% top-1
91.0%
84.3%
20× SMILES augmentation
Canonical targets · randomized inputs
Copy/pointer mechanism
80% of product atoms copied directly

Multi-model AI engine

RetroTransformer v2 (69.7% top-1) and RSGPT v6 LLM run in parallel with 20x SMILES augmentation and a copy/pointer mechanism. Complementary architectures maximize route coverage.

Protocol
Step 1 · Esterificationaspirin · 0.5 mmol
1

Weigh 2.0 g salicylic acid (14.5 mmol) into a 100 mL round-bottom flask.

2

Add 5 mL acetic anhydride and 5 drops conc. H₃PO₄.

3

Heat to 85 °C in a water bath for 15 min.

CorrosiveFume hood85 °C
TLC checkpoint
EtOAc:Hex 3:7 · Rf 0.45 (product)
Expected yield
Based on literature precedent
85%

AI-generated protocols

Step-by-step experimental procedures with exact reagent quantities, temperatures, TLC checkpoints, safety warnings, and expected yields / ready to execute in the lab.

Audit Trail
Route generated
Dr. Chen·14:32:01
a3f8c1…
Protocol approved
Dr. Patel·14:45:18
7b2e4d…
E-signature applied
Dr. Patel·14:45:22
9c1fa2…
Export to ELN
Dr. Chen·15:01:07
d4e7b8…
Electronic signature
21 CFR Part 11 compliant
Dr. Patel / Approved
Tamper-evident hash chain
4 entries verified · chain intact

21 CFR Part 11 compliance

Hash-linked audit trail, electronic signatures, tamper-evident logging, and full traceability for GxP-regulated environments. Every action is recorded and verifiable.

Ready to accelerate your synthesis?

Start with a free account. Input any target molecule and get AI-generated routes, protocols, and vendor sourcing in seconds.

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Scientist using Rasyn on a laptop