Several groups have used β-amino acids in the Ugi reaction to prepare β-lactams. 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: Combination of carbonyl compound and carboxylic acid Zhang et al. have combined aldehydes with carboxylic acids and used the Ugi reaction to create lactams of various sizes. Short et al. have prepared γ-lactams from keto-acids on solid-support. Applications Chemical libraries The Ugi reaction is one of the first reactions to be exploited explicitly to develop chemical libraries. These chemical libraries are sets of compounds that can be tested repeatedly. Using the principles of combinatorial chemistry, the Ugi reaction offers the possibility to synthesize a great number of compounds in one reaction, by the reaction of various ketones (or aldehydes), amines, isocyanides and carboxylic acids. These libraries can then be tested with enzymes or living organisms to find new active pharmaceutical substances. One drawback is the lack of chemical diversity of the products. Using the Ugi reaction in combination with other reactions enlarges the chemical diversity of possible products. Examples of Ugi reaction combinations: Isoquinolines from Ugi and Heck reactions. Pharmaceutical industry Crixivan can be prepared using the Ugi reaction. Additionally, many of the caine-type anesthetics are synthesized using this reaction. Examples include lidocaine and bupivacaine. See also Passerini reaction References Carbon-carbon bond forming reactions Multiple component reactions Name reactions Amide synthesis reactions