Ammonium Chloride Promoted Ugi Four-Component, Five-Center Reaction of α-Substituted α-Isocyano Acetic Acid:  A Strong Solvent Effect BonneDamien DekhaneMouloud ZhuJieping 2004 Conditions have been developed for the multicomponent synthesis of di- and tetrapeptide (<b>7</b>) based on the unique reactivity of α-isocyano acetic acid (<b>4</b> and its α -substituted derivatives) by an Ugi four-component, five-center reaction. Simply mixing <b>4</b>, a carbonyl compound (aldehyde or ketone, <b>8</b>), and a secondary amine (<b>9</b>) (ratio:  1:1:2) in toluene in the presence of 1.5 equiv of ammonium chloride afforded the desired product in good to excellent yield as a mixture of two diastereomers.