Tenofovir monohydrate
[CAS 206184-49-8]

Identification

• Classification: API >> Other chemicals
• Name: Tenofovir monohydrate
• Synonyms: [[(1R)-2-(6-Amino-9H-purin-9-yl)-1-methylethoxy]methyl]phosphonic acid monohydrate
• Molecular Formula: C₉H₁₄N₅O₄P.H₂O
• Molecular Weight: 305.23
• CAS Registry Number: 206184-49-8
• EC Number: 808-956-8
• SMILES: C[C@H](CN1C=NC2=C(N=CN=C21)N)OCP(=O)(O)O.O

Properties

• Solubility: DMSO: 100 mg/mL, Water: < 10 mg/mL (Expl.)

Safety Data

• Hazard Symbols: GHS06 Danger
• Risk Statements: H301
• Safety Statements: P264-P270-P301+P316-P321-P330-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	3	H301

chemBlink Chemical Story

Tenofovir monohydrate, CAS 206184-49-8, is the 1:1 hydrate of tenofovir, the acyclic nucleotide analogue also known as PMPA. FDA's Global Substance Registration System explicitly identifies this CAS number as tenofovir monohydrate and gives the composition C9H14N5O4P.H2O. The distinction from anhydrous tenofovir, CAS 147127-20-6, is a solid-state distinction: one water molecule is incorporated into the defined hydrated form.

The underlying antiviral chemistry belongs to tenofovir itself. After cellular uptake and phosphorylation, the pharmacologically active tenofovir diphosphate competes with natural nucleotide substrates of viral polymerases. Its phosphonate group is metabolically stable and central to nucleotide mimicry, but its strong ionization also limits passive membrane permeability. This conflict led to clinically important prodrugs such as tenofovir disoproxil and tenofovir alafenamide.

Why, then, distinguish a monohydrate? In pharmaceutical and process chemistry, crystal form matters. Incorporating water into a crystal lattice can alter melting behavior, hygroscopicity, density, solubility, mechanical properties and storage stability. Hydrate and anhydrate can interconvert depending on temperature and humidity, so controlling solid form is important for reproducible manufacture and analytical identification. The water is not a new pharmacophore; it is part of the crystalline material.

This distinction is especially useful in databases. "Tenofovir" may refer broadly to the active molecular framework, whereas CAS numbers can identify a particular hydration state. FDA GSRS maps CAS 206184-49-8 specifically to tenofovir hydrate/monohydrate and CAS 147127-20-6 to anhydrous tenofovir. Keeping those records separate avoids confusion in specifications and supply chains.

Tenofovir monohydrate therefore tells a solid-state chapter of an antiviral story. The medicinal chemistry explains why the tenofovir molecule inhibits viral replication; crystal chemistry explains why the same molecular entity may need a separate CAS identity when one equivalent of water becomes an integral, reproducible part of the solid.

References:
1. U.S. FDA GSRS, Tenofovir, UNII 99YXE507IL, CAS 206184-49-8.
2. PubChem, Tenofovir, CID 464205; related CAS 206184-49-8 (hydrate).
3. Byrn SR, Pfeiffer RR, Stowell JG. Solid-State Chemistry of Drugs. 2nd ed. SSCI, 1999.

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