5-Fluorouracil (5-FU)

Name: 5-Fluorouracil (5-FU)
Brand: Royalchem
Rating: 5.0 (7 reviews)

CAS NO. 51-21-8

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Brand:
Royalchem
Code:
51-21-8

Product Description

5-Fluorouracil (5-FU, CAS 51-21-8) is a fluorinated analogue of uracil. It is an established anticancer drug substance and the fluoropyrimidine starting material for flucytosine, tegafur and 2,4-dichloro-5-fluoropyrimidine. Royalchem quotes 5-FU for pharmaceutical synthesis and research, with batch COA and SDS.

Product Name	5-Fluorouracil (5-FU) Also: Fluorouracil; 5-Fluoro-1H-pyrimidine-2,4-dione; 5-Fluoro-2,4(1H,3H)-pyrimidinedione
Identifiers	CAS 51-21-8 \| EC No. 200-085-6 \| MDL MFCD00006018
Formula / MW	C₄H₃FN₂O₂ / 130.08
Structure
Properties	White to almost white crystalline powder; mp 282–286 °C (dec.); sparingly soluble in water (about 12 g/L at 20 °C), soluble in DMSO, DMF and dilute ammonia; light sensitive.
Grade	Synthesis, research or pharmacopoeial grade — confirmed at quotation. Assay alone does not make a product USP / EP or GMP API grade; those claims apply only when stated on the quote and supported by documents.

Specification

Specification on request. Please state your required assay (HPLC), related substances, loss on drying, residue on ignition and documents (COA, SDS, USP / EP compliance). The supplier batch COA governs.

Applications

Flucytosine (5-FC): chlorination with POCl₃ gives 2,4-dichloro-5-fluoropyrimidine; amination and hydrolysis give the antifungal flucytosine.
Tegafur and fluorinated nucleosides: N-alkylation of 5-FU gives the oral prodrug tegafur; glycosylation gives nucleosides such as floxuridine.
Fluoropyrimidine building block: 2,4-dichloro-5-fluoropyrimidine (CAS 2927-71-1) from 5-FU is a versatile intermediate for substituted 5-fluoropyrimidines.
Oncology research: reference thymidylate synthase inhibitor in cell and pharmacology studies.

5-Fluorouracil vs Flucytosine

Item	5-Fluorouracil (5-FU)	Flucytosine (5-FC)
CAS	51-21-8	2022-85-7
Formula	C₄H₃FN₂O₂	C₄H₄FN₃O
Main use	Anticancer drug; starting material	Antifungal drug; capecitabine / emtricitabine intermediate
Link	Different compounds, not interchangeable. 5-FU can be converted chemically to 5-FC; inside fungal cells, 5-FC is converted to 5-FU.

Packing, Storage & Transport

Packing	UN-approved packaging for Class 6.1 solids; pack size per order.
Storage	Tightly closed, locked up, protected from light, in a cool, dry, ventilated place away from strong oxidizers and bases.
Transport	Dangerous goods: UN 2811, Toxic solid, organic, n.o.s. (5-Fluorouracil), Class 6.1, PG III. Batch SDS and carrier requirements govern.

Safety: GHS Danger — toxic if swallowed; SDS also list mutagenic, carcinogenic and reproductive hazards. Handle as a cytotoxic compound: avoid dust, use containment, gloves, eye and respiratory protection. See the SDS.

Sourcing 5-Fluorouracil for flucytosine, tegafur or research?
Royalchem quotes 5-FU (CAS 51-21-8) with batch COA and SDS, shipped as UN 2811 dangerous goods. Please tell us your intended use, required assay and impurity limits, documents and quantity.

FAQ

What is 5-Fluorouracil (CAS 51-21-8)?	5-Fluorouracil (5-FU) is 5-fluoro-1H-pyrimidine-2,4-dione, C₄H₃FN₂O₂, MW 130.08 — a white crystalline powder (mp 282–286 °C, dec.). It is an anticancer drug substance and a starting material for other fluoropyrimidines.
Is 5-Fluorouracil the same as flucytosine?	No. 5-Fluorouracil (5-FU, CAS 51-21-8) and flucytosine (5-FC, CAS 2022-85-7) are different compounds. 5-FU can be converted chemically to 5-FC.
What is 5-FU used to make?	Flucytosine (via 2,4-dichloro-5-fluoropyrimidine), the prodrug tegafur, fluorinated nucleosides such as floxuridine, and other substituted 5-fluoropyrimidines.
Is 5-Fluorouracil hazardous to ship?	Yes. It ships as UN 2811, Toxic solid, organic, n.o.s., Class 6.1, Packing Group III, and is classified GHS Danger (toxic if swallowed).
Does ≥99% assay mean USP or EP grade?	No. USP / EP grade requires meeting the full monograph with supporting documents. Tell us the grade you need; batch COA and SDS come with every shipment.