amides derived from two or more amino carboxylic acid molecules (the same or different) by formation of a covalent bond from the carbonyl carbon of one to the nitrogen atom of another with formal loss of water. The term is usually applied to structures formed from α-amino acids, but it includes those derived from any amino carboxylic acid.
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(R may be any organyl group, commonly but not necessarily one found in natural amino acids).
See also: proteins, retro, carboxylic acids
Sources:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1356 (https://doi.org/10.1351/pac199567081307)
White Book, 2nd ed., p. 48 (https://www.qmul.ac.uk/bibliog/white.html)