Several groups have used β-amino acids in the Ugi reaction to prepare β-lactams.[19] This approach relies on acyl transfer in the Mumm rearrangement to form the four-membered ring. The reaction proceeds in moderate yield at room temperature in methanol with formaldehyde or a variety of aryl aldehydes. For example, p-nitrobenzaldehyde reacts to form the β-lactam shown in 71% yield as a 4:1 diastereomeric mixture: