# An Unorthodox Enolate–Triggered Radical Relay Directs the Chemo Upgrading of Levulinic Acid Into Citramalic Acid

## TL;DR

A new chemical method converts levulinic acid into citramalic acid using a radical pathway and enolate chemistry, offering a sustainable route for producing valuable chemicals.

## Contribution

A transition-metal-free, scalable method for converting levulinic acid into citramalic acid via an unorthodox enolate and radical pathway is introduced.

## Key findings

- Potassium tert-butoxide and molecular oxygen enable the selective transformation of levulinic acid into citramalic acid.
- Radical intermediates are involved in the oxygenation sequence, as shown by TEMPO and benzoic acid trapping experiments.
- Citramalic acid is a sustainable platform chemical for producing high-value feedstocks like itaconic acid and amino acid derivatives.

## Abstract

We report a transition‐metal‐free and highly selective chemical transformation of levulinic acid into citramalic acid via t‐butoxide‐mediated enolate chemistry, complementing both the biotransformation of glucose and glycerol using E. coli as well as transition‐metal‐catalyzed processes based on levulinic acid. The atypical behavior of t‐butoxide—classically recognized as a base that favors kinetic enolate formation in carbonyl chemistry—proves crucial for accessing the thermodynamic enolate under elevated temperatures and extended reaction times, thereby directing the reaction toward citramalic acid as the major product. Radical‐trapping experiments with TEMPO (2,2,6,6‐tetramethylpiperidine 1‐oxyl) and benzoic acid significantly diminished the product yield, indicating the involvement of radical intermediates in the initial oxygenation sequence and providing clear mechanistic insight into the operative pathway. Moreover, citramalic acid serves as a sustainable, bio‐based platform chemical that is amenable to downstream valorization into high‐value feedstocks, such as unnatural amino acid derivative and itaconic acid.

Unorthodox Thermodynamic
Enolate Coupled with a Radical Pathway A transition‐metal‐free oxidation of biomass‐derived levulinic acid to citramalic acid is achieved through an unorthodox enolate in combination with a radical pathway using potassium tert‐butoxide (KOtBu) and molecular oxygen (O2). The transformation is readily scalable and provides citramalic acid as a versatile platform for accessing propene precursors, unnatural amino acid derivatives, and itaconic acid.© 2026 WILEY‐VCH GmbH