Bioactive peptides (BP) are organic substances formed by amino acids joined by covalent bonds known as amide or peptide bonds. Although some BP exist free in its natural source, the vast majority of known BP are encrypted in the structure of the parent proteins and are released mainly by enzymatic processes. Some BP have been prepared by chemical synthesis. BP play a significant role in human health by affecting the digestive, endocrine, cardiovascular, immune, and nervous systems. BP are considered the new generation of biologically active regulators; they can prevent oxidation and microbial degradation in foods and also improve the treatment of various diseases and disorders, thus increasing the quality of life. The growing interest in BP has incentivized the scientific community and the food industry to exploring the development of new food additives and functional products based on these peptides. The present review highlights the recent findings on the identification, bioassays, and use of BP, as well as their potential use as food additives and in the development of functional products.

A convenient base-mediated two-step synthesis of cotinine analogs and a one-pot base-free synthesis of iso-cotinine derivatives featuring an Ugi-4CR/cyclization protocol are reported. These approaches exploit the reactivity of the peptidyl position present in the Ugi adducts, allowing the facile construction of the γ-lactam core, as well as the introduction of a N-substituted methyl group into the analogs in a straightforward manner. A plausible mechanism for the cyclization step is discussed.

A very simple, yet efficient synthetic methodology, to obtain 3,4-diaryl-substituted pyrroles is described. The approach is based on the Knoevenagel condensation between arylacetonitriles and substituted aromatic aldehydes, followed by conjugate addition of cyanide to afford succinonitriles in excellent yields. The products thus obtained were subjected to DIBAL-H reduction, followed by cyclization under acidic conditions to produce the corresponding pyrroles in good overall yields. The utility of this protocol is exemplified by the synthesis of the marine alkaloids lamellarins O and Q.

A practical one-pot synthesis of nicotine analogs from Ugi 4-CR/propargyl adducts is reported. This methodology allows the rapid construction of the pyrrolidine moiety present in nicotine through an intramolecular base-promoted 5-endo cycloisomerization process, followed by a reduction of the resulting mixture of 2- and 3-pyrrolines to afford nicotine analogs in good overall yields.

Palladium (Pd) coupling reactions have become an indispensable tool in modern synthetic organic chemistry. A simple procedure to obtain isoindolinones 7 bearing a quaternary C-atom, featuring a Pd-mediated tandem process, is presented. Readily available iodoamidoacrylate 3 and boronic acids 6 are used as the starting materials.

8-Methoxy-1-tetralone was synthesized in a concise and efficient manner involving a sequential palladium-mediated cross-coupling reaction (Heck), catalytic hydrogenation, and intramolecular acylation mediated by Eaton’s reagent or Lewis acids. The pivotal step in the synthesis was the use of a bromine substituent at the benzenoid C4 position of the intermediate methyl 4-arylbutyric ester to ensure cyclization ortho to the methoxy moiety and obviate cyclization at the para position to the thermodynamically preferred 6-methoxy-1-tetralone, the sole product obtained in the absence of this blocking group.