20-(tert-Butoxy)-20-oxoicosanoic Acid 683239-16-9: Uses & Structure

2026.08.20

20-(tert-Butoxy)-20-oxoicosanoic Acid (CAS 683239-16-9): Structure, Uses and Research Applications

20-(tert-Butoxy)-20-oxoicosanoic acid, CAS 683239-16-9, is a mono-protected C20 dicarboxylic acid derivative. It is also commonly referred to as Eicosanedioic Acid Mono-tert-butyl Ester.

PubChem lists the compound with the molecular formula C₂₄H₄₆O₄ and a molecular weight of 398.6 g/mol. Its structure contains a long C20 framework with one free carboxylic acid group and one terminal carboxyl group protected as a tert-butyl ester.

That combination is what makes the molecule useful. Rather than behaving as a symmetric diacid, it gives chemists two differently protected ends to work with during multistep molecular design.

What Makes the Structure Different?

The parent compound, Eicosanedioic Acid, contains two free terminal carboxyl groups. In 20-(tert-Butoxy)-20-oxoicosanoic acid, one of those groups is temporarily protected.

A simple way to view the structure is:

Free COOH → C20 long-chain framework → tert-butyl-protected carboxyl group

This makes the compound relevant when a synthetic route requires one end of a long-chain diacid to remain available while the second end is held in a protected state.

Main 20-(tert-Butoxy)-20-oxoicosanoic Acid Uses

Long-Chain Functional Intermediates

As a long-chain dicarboxylic acid intermediate, CAS 683239-16-9 can be evaluated as a C20 building block for more complex functional structures.

The free carboxyl group provides a point for downstream modification, while the protected end allows the molecule to retain differentiated terminal functionality.

Multistep Organic Chemistry

Mono-protection is particularly useful when a project involves sequential reactions.

Instead of working with two similar carboxyl groups at the same time, researchers can address the free end first and process the protected end later according to the route design.

Fatty-Acid Side-Chain Research

CAS 683239-16-9 also appears in published peptide-related side-chain chemistry. A U.S. patent application describing a Tirzepatide preparation route specifically uses 20-(tert-butoxy)-20-oxoicosanoic acid during construction of a C20-containing side-chain moiety.

This does not make the material a complete peptide side chain. It is one upstream C20 structural building block within a larger sequence of intermediates.

For a closer look at this application, see our guide to CAS 683239-16-9 in Tirzepatide side-chain chemistry

What Should Be Checked Before Use?

For technical evaluation, confirm the exact CAS number, molecular identity, protection state and batch specification.

This is particularly important with long-chain diacids because the free acid, mono-protected derivative and more advanced side-chain intermediates may have closely related names but different roles in a synthetic route.

FAQ

Is Eicosanedioic Acid Mono-tert-butyl Ester the same as CAS 683239-16-9?
Yes. PubChem includes icosanedioic acid mono-tert-butyl ester and Eicosanedioic Acid Mono-Tert-Butyl Ester among the synonyms associated with this compound.

Why is one carboxyl group protected?
The protected terminus allows the two ends of the C20 framework to be differentiated during multistep structural modification.

For project evaluation, product identity, purity and batch-specific analytical information should be reviewed against the intended downstream process.

For research use only.