Bond, Link amide

A key biochemical reaction of ammo acids is their conversion to peptides polypeptides and proteins In all these substances ammo acids are linked together by amide bonds The amide bond between the ammo group of one ammo acid and the carboxyl of another IS called a peptide bond Alanylglycme is a representative dipeptide... 

When an amine reacts with an acid chloride, an amide is formed. What would happen, though, if a diamine and a diacid chloride were allowed to react Each partner could form two amide bonds, linking more and more molecules together until a giant polyamide resulted. In the same way, reaction of a diol with a diacid would lead to a polyester. 

It was anticipated that fragments 147 and 214 could be united through an amide bond linking the nitrogen atom of the latter with C-8 of the former. Indeed, the active ester formed by treatment of carboxylic acid 147 with 1,3-diisopropylcarbodiimide and 1-hydro-xybenzotriazole reacts efficiently with amine 214 to afford dihydroxy amide 215 in 95 % yield. This convergent union creates a molecule that possesses all but two carbon atoms of the natural product. 

In the following sections, we discuss compounds whose amide group is adjacent to an aromatic system. A distinction is made between aromatic amides derived from aromatic acids (e.g., benzamides) or from aromatic amines (e.g., anilides). The discussion will be completed with compounds in which the amide bond links two aromatic systems. 

Having discussed amides that carry an aromatic group on either the nitrogen or the carboxy side of the amide bond (i.e., anilides or benzamides, respectively), we continue our presentation with compounds in which the amide bond links two aromatic systems. The simplest structure in this class is A-phenylbenzamide (4.154). The influence of the nature and position of substitution on the rate of hydrolysis of a series of A-phenylbenzamides was investigated in mouse and sheep liver homogenates, with the goal of elucidating the metabolism of the anthelminthic niclosamide (4.158) [102],... 

Due to the vast numbers and rapidity of novel developments in solid-phase synthesis over the past ten years, a number of reports currently found in the literature deal with solid-phase syntheses of lanthionine peptides. There are at least two different approaches to synthesize lanthionine peptides in which the sulfide bond links amino acid halves that are not direct neighbors within the peptide chain (Scheme 10). One obvious approach, method A, is based on the coupling of a preformed, orthogonally protected lanthionine monomer to the N-terminus of a peptide oxime resin. 48 This is then followed by acid-catalyzed cyclization and simultaneous release from the resin during amide bond formation with the C-terminal carboxy group via the peptide cyclization method on oxime resin (see Section 6.73.2.2). The alternative approach is lanthionine formation after peptide synthesis from amino acid derivatives, such as serine and cysteine (method B). 

The conclusions drawn from the data are that in terms of structural or electrostatic interactions with this antagonist site on the receptor, the amide bond linking residues two and three may not be as critical as those linking residues three to four and four to five. 

In this assay, enzymes with chymotrypsin-like specificity readily bind the side chain of Phe at the primary substrate binding site (SI) and subsequently hydrolyze the adjacent amide bond linking the Phe residue to the p-NA moiety. On cleavage, the release of p-NA is measured by the increase in absorbance at 410 nm (e4l0 = 8480 M 1 cm-1) with time, using a recording spectrophotometer. 

The planarity of the amide linkers in the protein backbone restricts rotation around the carbon-nitrogen bond. This provides some restrictions on the number of conformers that can be adopted. The linkage joining amino acids in a polymer is quite stable, but not infinitely so, and it can be relatively easily hydrolyzed by enzymes to allow turnover of proteins within cells. This propitious combination of properties is conferred by the amide bonds linking the amino acids in the polymer polymers linked by ester, thioester, ether, or carbon-carbon bonds lack one or more these properties. 

Aakeroy et al. were also able to prepare building blocks based upon Ag(I) centres coordinated in a trigonal planar manner by three isonicotinamide ligands. The isostructural perchlorate and tetrafluoroborate salts of these cationic complexes involve amide-amide hydrogen-bonded links from each cation to six others, resulting in 3D interpenetrated networks that resemble the network found in a-ThSi [53]. 

Figure 20 Part of the four-fold interpenetrated 3D diamondoid network formed by [Cu(L)4]+ [L = 3-cyano-6-methylpyrid-2(l//)-one] as its PF6 salt [58], Hydrogen-bonded links are provided by R2(8) synthons involving all amide groups. Oxygen, nitrogen and key hydrogen atoms are shaded.

Rg. 1.24 Key interactions between the active enantiomer BMS270394 and RAR-y. A key interaction involves a hydrogen bond between the ligand hydroxyl group and the sulfur of Met-272. Notice that the linking amide group makes complementary interactions with the enzyme. 

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