Rezafungin acetate
[CAS 1631754-41-0]

Identification

• Classification: Organic raw materials >> Carboxylic compounds and derivatives >> Carboxylic esters and their derivatives
• Name: Rezafungin acetate
• Synonyms: 2-[[(3S,9S,11R,15S,18S,20R,21R,24S,25S,26S)-6-[(1S,2S)-1,2-dihydroxy-2-(4-hydroxyphenyl)ethyl]-11,20,25-trihydroxy-3,15-bis[(1R)-1-hydroxyethyl]-26-methyl-2,5,8,14,17,23-hexaoxo-18-[[4-[4-(4-pentoxyphenyl)phenyl]benzoyl]amino]-1,4,7,13,16,22-hexazatricyclo[22.3.0.09,13]heptacosan-21-yl]oxy]ethyl-trimethylazanium;acetate
• Molecular Formula: C₆₅H₈₈N₈O₁₉
• Molecular Weight: 1285.44
• CAS Registry Number: 1631754-41-0
• SMILES: CCCCCOC1=CC=C(C=C1)C2=CC=C(C=C2)C3=CC=C(C=C3)C(=O)N[C@H]4C[C@H]([C@H](NC(=O)[C@@H]5[C@H]([C@H](CN5C(=O)[C@@H](NC(=O)[C@@H](NC(=O)[C@@H]6C[C@H](CN6C(=O)[C@@H](NC4=O)[C@@H](C)O)O)[C@@H]([C@H](C7=CC=C(C=C7)O)O)O)[C@@H](C)O)C)O)OCC[N+](C)(C)C)O.CC(=O)[O-]

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H302-H315-H319-H335
• Safety Statements: P261-P280-P301+P312-P302+P352-P305+P351+P338

chemBlink Chemical Story

Rezafungin acetate is the acetate salt associated with rezafungin, a long-acting echinocandin antifungal developed as CD101 and Biafungin. Echinocandins inhibit fungal beta-(1,3)-D-glucan synthase, weakening synthesis of an essential fungal cell-wall polymer absent from human cells. Rezafungin was engineered for improved chemical stability and a prolonged pharmacokinetic profile enabling once-weekly intravenous administration. FDA approved REZZAYO in March 2023 for adults with candidemia and invasive candidiasis who have limited or no alternative treatment options. The acetate counterion belongs to the drug-substance salt identity; pharmacological activity is attributed to rezafungin.

The exact registry identity matters because related free forms, salts, hydrates, stereoisomers, process intermediates and finished medicines can have separate CAS numbers even when their names share a familiar stem. In pharmaceutical and fine-chemical work this distinction is practical: composition changes formula weight and can alter solubility, crystallization, analytical standards, manufacturing specifications and interpretation of physical-property data.

The molecule also illustrates how chemists use functional groups as deliberate handles. Aromatic rings and heterocycles establish shape and electronic character, while amines, alcohols, carbonyl groups, carboxylic acids, esters or ionic centers control reactivity and intermolecular interactions. In a multistep route, an intermediate may be valuable precisely because one group can be transformed selectively while another survives for a later operation.

Modern development is equally an analytical problem. Chemists must demonstrate identity and purity, control stereochemistry or salt composition where relevant, follow process-related impurities and establish reproducible specifications. Reference materials and isolated intermediates therefore have scientific importance even when they are never administered to a patient or sold as the final commercial product.

A careful Chemical Story must distinguish documented use from structural possibility. A familiar scaffold can suggest a biological hypothesis, but resemblance is not evidence that the exact CAS substance has been tested, approved or commercially adopted for that purpose. The account therefore emphasizes verified identity, development history and supported applications, and deliberately leaves unsupported claims out.

Seen more broadly, the compound shows that useful molecular design rarely depends on one functional group in isolation. Performance emerges from the whole structure, stereochemistry and physical form, the route used to make it, and the environment in which it operates. Connecting those molecular details to a real manufacturing, analytical or therapeutic role turns a technical registry entry into a meaningful chemical story.

The exact registry identity matters because related free forms, salts, hydrates, stereoisomers, process intermediates and finished medicines can have separate CAS numbers even when their names share a familiar stem. In pharmaceutical and fine-chemical work this distinction is practical: composition changes formula weight and can alter solubility, crystallization, analytical standards, manufacturing specifications and interpretation of physical-property data.

The molecule also illustrates how chemists use functional groups as deliberate handles. Aromatic rings and heterocycles establish shape and electronic character, while amines, alcohols, carbonyl groups, carboxylic acids, esters or ionic centers control reactivity and intermolecular interactions. In a multistep route, an intermediate may be valuable precisely because one group can be transformed selectively while another survives for a later operation.

Modern development is equally an analytical problem. Chemists must demonstrate identity and purity, control stereochemistry or salt composition where relevant, follow process-related impurities and establish reproducible specifications. Reference materials and isolated intermediates therefore have scientific importance even when they are never administered to a patient or sold as the final commercial product.

References:
1. U.S. FDA. Integrated Review: REZZAYO, NDA 217417, 2023.
2. U.S. FDA. Drug Trials Snapshots: REZZAYO.
3. FDA GSRS. Rezafungin acetate.

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