Cyclic Imines in Ugi and Ugi-Type Reactions.

Area of Science:

• Organic Chemistry
• Medicinal Chemistry
• Synthetic Chemistry

Background:

• Ugi four-component reactions (U-4CRs) efficiently synthesize pseudopeptides but lack conformational restriction for drug development.
• The conformational rigidity of drug candidates is crucial for potent biological target interactions.

Purpose of the Study:

• To review the redesign of synthetic routes for Joullié-Ugi three-component reactions (JU-3CRs).
• To highlight the preparation of diverse heterocyclic compounds linked to peptide backbones.
• To explore novel N-heterocycles with pharmaceutical significance.

Main Methods:

• Utilizing cyclic imines in place of amine/oxo components in Ugi reactions to form JU-3CRs.
• Replacing α-acidic isocyanides or azides with standard isocyanides or acids.
• Synthesizing three-, five-, six-, and seven-membered heterocyclic compounds.

Main Results:

• JU-3CRs offer a robust single-step synthesis of peptide-N-heterocycle conjugates.
• JU-3CRs exhibit superior diastereoselectivity compared to U-4CRs.
• The approach enables the synthesis of N-heterocycles attached to oxazoles or tetrazoles.

Conclusions:

• JU-3CRs provide a versatile platform for generating conformationally restricted molecules.
• This methodology facilitates the creation of diverse libraries of natural products and drug-like compounds.
• The review serves as a guide for chemists designing novel synthetic strategies.