Synthesis of Unnatural Amino Acids via β‐Aminoaldehyde C–H Arylation using HAT‐Metallaphotoredox Catalysis

Abstract Unnatural amino acids play a crucial role in advancing protein engineering and drug development. In this study, we present the synthesis of a series of γ‐aryl‐keto‐α‐amino acids through the direct C−H arylation of readily accessible β‐aminoaldehydes and aryl bromides, promoted by hydrogen atom transfer combined with metallaphotoredox catalysis. This direct and mild methodology provides access to enantiopure L‐ and D‐ amino acids, either N ‐protected or unprotected, with broad functional group compatibility, including pyridine heterocycles. These features highlight the potential relevance of this strategy for pharmaceutical synthesis and biotechnological research.