Photo-induced coupling of tertiary amines with Ugi-derived dehydroalanines as a practical device in the synthesis to 2,4-diaminobutyric acid derivatives

An lr-mediated photocatalytic coupling of tertiary amines with Ugi-dehydroalanines was developed as an entry to medicinally important 2,4-diaminobutyric acid derivatives. In the process the 2,4-diaminobutyric acid framework is assembled directly embedded into a peptoide structure, via the construction of the C-3(sp(3))-C-4(sp(3)) bond, through a C-H functionalization. The photocatalyzed oxidation of the tertiary amine produce a free radical intermediate which reacts with the double bond present in the dehydroalanines. The complete protocol comprises an Ugi 4-CR followed by an elimination reaction and the photo induced coupling. Using this strategy, 15 new diversely substituted unnatural alpha,gamma-diamino acids peptide derivatives were prepared in low to good yields. (C) 2019 Elsevier Ltd. All rights reserved.