Four-component condensation (Ugi reaction) at high pressure: novel synthesis of peptides containing very bulky α,α-disubstituted glycines

Abstract
Peptides, Z-Val-X-Gly-OMe, containing a very bulky α,α-disubstituted glycine, such as N-benzyl-α,α-diisopropylglycine or N-benzyl-α,α-diphenylglycine, as the residue X can be synthesized in moderate yields by four-component condensation (Ugi reaction) at high pressure (9 kbar, 0.9 GPa).