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Updated: Jun 19, 2026

Preparation of Stable Bicyclic Aziridinium Ions and Their Ring-Opening for the Synthesis of Azaheterocycles
Published on: August 22, 2018
Rapid access to N-substituted diketopiperazines by one-pot Ugi-4CR/deprotection+activation/cyclization (UDAC)
Cristiano R B Rhoden1, Daniel G Rivera, Oliver Kreye
1Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, Weinberg 3, D-06120, Halle (Saale), Germany.
Abstract:
The most efficient diversity generating approaches to heterocycles are combinations of a multicomponent (MCR) with a cyclization reaction, for example, by Ugi-deprotection-cylization (UDC) protocols. If the desired post-Ugi reaction requires more than one deprotection, for example of two initially protected Ugi-reactive groups, or if it requires additional activation, for example, by an Ugi-activation-cyclization (UAC), either the isolation of intermediates or a sequential process or both become necessary. A recently introduced convertible isonitrile reagent allows a mild and chemoselective in situ post-Ugi activation of the isonitrile-born carboxylate with simultaneous deprotection of the nucleophilic amine, that is, liberation and activation of two Ugi-reactive groups, if desired also under subsequent lactam formation. This is exemplified by the synthesis of peptide-peptoid diketopiperazines.
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