Role of hydrogen bonding in the selectivity of aromatic Mannich reaction of tyramines: Macrocyclization vs. linear condensation

Enhancement of the Antioxidant and Antimicrobial Activities of Porphyran through Chemical Modification with Tyrosine Derivatives

“…The electron density on the aromatic ring can be gauged by the pKa of the phenolic hydroxyl group, as the increased aromatic ring substitution with electron-donating alkyl groups is reported to increase the pKa of the phenol [ 46 , 47 , 48 , 49 ]. In turn, a higher pKa can indicate an increased reactivity of the phenol towards electrophilic aromatic substitution reactions, [ 50 , 51 , 52 ] as is the case of the phenolic Mannich reaction [ 53 ].…”

“…To minimize this occurrence, formaldehyde was the last reagent to be added to the reaction mixture. The objective of this reagent addition order was to favor the rapid scavenging of the disodium tyrosinate imine electrophile upon its formation by the disubstituted phenols [ 53 ].…”

“…The regioselectivity of this reaction was checked by NMR ( Figures S2–S4 ), namely by heteronuclear multiple bond correlation (HMBC). The HMBC spectrum of L2 in acidic acetone presented 3-bond correlations which indicated that the reaction proceeded with the desired regioselectivity [ 53 ].…”

“…To minimize this occurrence, formaldehyde was the last reagent to be added to the reaction mixture. The objective of this reagent addition order was to favor the rapid scavenging of the disodium tyrosinate imine electrophile upon its formation by the disubstituted phenols [53]. The selectivity of this reaction towards the formation of the desired product relied on the different nucleophilic characters of the disubstituted phenols and the side chain of tyrosine.…”

Synthesis, characterization and biological activity of new complexes from Manniche base ligands derived from amoxicillin

“…The name of this type of interaction was associated with the name of the first scientist concerned with its study, C. Manniche (5). Manniche's rules have been classified as popular compounds for a long time, and interest in these compounds continues due to their effectiveness in the pharmaceutical fields (6,7) and their industrial applications, such as polymers used in coatings and coatings as their applications in various areas. Manniche bases have been used in soil chemistry, where Manniche base compounds regulate plant growth (8), and as auxiliary and bonding materials in polymer chemistry (9).…”