Amide linearity

Among the different types of compounds whose complexation properties have been studied are various amides linear oxoamide 9 [22], fumaramide 10 [23,24] and methanetricarboxamide 11 [25], biphenyl derivatives 12 [26], and derivatives of tartaric acid 13-16, that can also be prepared in an optically active form [27], The above-mentioned chiral hosts have been found to form inclusion complexes with chiral guests 17 and 18. Molecular recognition between chiral hosts and... 

ANTHELMINTIC which was never marketed, helodermin is a 35 amino acid residue Af-terminally amidated linear peptide, isolated from the venom of the Gila monster Heloderma suspectum. It is a vasoactive intestinal PEPTIDE RECEPTOR AGONIST and Stimulates adenylate cyclase in rat pancreatic membranes. 

Much of protein engineering concerns attempts to explore the relationship between protein stmcture and function. Proteins are polymers of amino acids (qv), which have general stmcture +H3N—CHR—COO , where R, the amino acid side chain, determines the unique identity and hence the stmcture and reactivity of the amino acid (Fig. 1, Table 1). Formation of a polypeptide or protein from the constituent amino acids involves the condensation of the amino-nitrogen of one residue to the carboxylate-carbon of another residue to form an amide, also called peptide, bond and water. The linear order in which amino acids are linked in the protein is called the primary stmcture of the protein or, more commonly, the amino acid sequence. Only 20 amino acid stmctures are used commonly in the cellular biosynthesis of proteins (qv). 

Dialkyl and diarylthaHium(III) derivatives are stable, crystalline soHds that melt at 180—300°C. The dimethylthaHium derivatives of CN , CIO, BF, and NO 2 contain linear (CH2)2T1 cations and the free anions (19). In aqueous solutions, they ionize to the (CH2)2T1(H20) ions, except those derivatives containing alkoxide, mercaptide, or amide anions, which yield dimeric stmctures (20,21). 

Caprolactam is an amide and, therefore, undergoes the reactions of this class of compounds. It can be hydrolyzed, Ai-alkylated, O-alkylated, nitrosated, halogenated, and subjected to many other reactions (3). Caprolactam is readily converted to high molecular weight, linear nylon-6 polymers. Through a complex series of reactions, caprolactam can be converted to the biologically and nutritionally essential amino acid L-lysine (10) (see Amino acids). 

The role of IR spectroscopy in the early penicillin structure studies has been described (B-49MI51103) and the results of more recent work have been summarized (B-72MI51101). The most noteworthy aspect of a penicillin IR spectrum is the stretching frequency of the /3-lactam carbonyl, which comes at approximately 1780 cm" This is in contrast to a linear tertiary amide which absorbs at approximately 1650 cm and a /3-lactam which is not fused to another ring (e.g. benzyldethiopenicillin), which absorbs at approximately 1740 cm (the exact absorption frequency will, of course, depend upon the specific compound and technique of spectrum determination). The /3-lactam carbonyl absorptions of penicillin sulfoxides and sulfones occur at approximately 1805 and 1810 cm respectively. The high absorption frequency of the penicillin /3-lactam carbonyl is interpreted in terms of the increased double bond character of that bond as a consequence of decreased amide resonance, as discussed in the X-ray crystallographic section. Other aspects of the penicillin IR spectrum, e.g. the side chain amide absorptions at approximately 1680 and 1510 cm and the carboxylate absorption at approximately 1610 cm are as expected. 

The addition of phenylisocyanate to aldehyde-derived enamines resulted in the formation of aminobutyrolactams (438,439). As aminal derivatives these produets can be hydrolyzed to the linear aldehyde amides and thus furnish a route to derivatives of the synthetically valuable malonaldehyde-acid system. With this class of reactions, a second acylation on nitrogen becomes possible and the six-membered cyclization products have been reported (440). Closely related to the reactions of enamines with isocyanates is the condensation of cyclohexanone with urea in base (441). 

The reaction of ACPC with linear aliphatic amines has been investigated in a number of Ueda s papers [17,35,36]. Thus, ACPC was used for a interfacia] polycondensation with hexamethylene diamine at room temperature [17] yielding poly(amide)s. The polymeric material formed carried one azo group per repeating unit and exhibited a high thermal reactivity. By addition of styrene and methyl methacrylate to the MAI and heating, the respective block copolymers were formed. 

Fig. 3.3.4 Reaction mechanism of the coelenterazine bioluminescence showing two possible routes of peroxide decomposition, the dioxetanone pathway (upper route) and linear decomposition pathway (lower route). The Oplopborus bioluminescence takes place via the dioxetanone pathway. The light emitter is considered to be the amide-anion of coelenteramide (see Section 5.4).

The best results were obtained with amides of (S)- or (/ )-3-methoxy-l-phenyl-2-propylamine, which gave, with linear aliphatic aldehydes, products with enantiomeric excesses greater than 75% using titanium(IV) chloride as the Lewis acid. A transition state involving coordination of the titanium by the carbonyl oxygens of both the amide and the aldehyde was proposed95. 

Another important type of condensation polymer are the linear polyesters, such as poly (ethylene terephthalate) (PET) and poly (butylene terephthalate) (PBT). Copolymers of polyesters and PA have been studied in detail, and it has been shown that random copolyesteramides have a low structural order and a low melting temperature. This is even the case for structurally similar systems such as when the group between the ester unit is the same as that between the amide unit, as in caprolactam-caprolactone copolymers (Fig. 3.10).22 Esters and amide units have different cell structures and the structures are not therefore isomorphous. If block copolymers are formed of ester and amide segments, then two melting temperatures are present. 

The second problem involves the measurement of pKa values for carbonyl and thiocarbonyl derivatives. Grieg and Johnson (157) have pointed out that the measurement of pKa values for very weak bases (11) is an inaccurate and arbitrary process. Of particular difficulty for our purposes is the fact that different carbonyl derivatives may require different acidity functions. As a result of this situation, no attempt was made to make correlations of pKa data for carbonyl and thiocarbonyl derivatives with eq. (2). Because accurate pKa values can be measured for imines, these values were correlated with eq. (2), although the conformational problem remains. The imine sets were first studied by Charton and Charton (73), who correlated them with eq. (2). No correlations of data for carbonyl or thiocarbonyl derivatives with eq. (2) are extant in the literature. Bhaskar, Gosavi, and Rao (158) have reported that AG values for complex formation of substituted thioureas with iodine are a linear function of the Taft a values. Drago, Wenz, and Carlson (159) have reported similar results for complex formation between iodine and substituted amides. Oloffson (160) has reported a linear relationship between -AH for the complex of substituted N,N-dimethylamides with SbCls and the ffj constants. 

The catalytic hydroformylation of alkenes has been extensively studied. The selective formation of linear versus branched aldehydes is of capital relevance, and this selectivity is influenced by many factors such as the configuration of the ligands in the metallic catalysts, i.e., its bite angle, flexibility, and electronic properties [152,153]. A series of phosphinous amide ligands have been developed for influencing the direction of approach of the substrate to the active catalyst and, therefore, on the selectivity of the reaction. The use of Rh(I) catalysts bearing the ligands in Scheme 34, that is the phosphinous amides 37 (R ... 

A number of amide- and ester-linked fatty acids and (/ )-3-hydroxy acids are components of the lipid A part in the LPS from Gram-negative bacteria. The acids have been tabulatedand the chemistry of lipid A summarized. The most common acids in lipid A from Enterobacteriaceae are the saturated 12 0,14 0, and 16 0, and the (/ )-3-hydroxy-14 0, The last is linked to N-2 and 0-3 of the 2-amino-2-deoxy-D-glucopyranosyl residues, and the others are ester-linked to the hydroxy acid, as in the lipid A (44) of Salmonella minnesota. Other linear and branched fatty acids, unsaturated acids, S)-2- and (/ )-3-hydroxy acids, and 3-oxotetradecanoic acid are components of lipid A from certain different species. In the lipid A from Rhizobium trifolii, 2,7-dihydroxyoctanoic acid is linked as amide to a 2-amino-2-deoxy-D-gl ucopy ranosy 1 residue. ... 

Listowsky and coworkers showed that the c.d. of this sugar derivative is due entirely to lactic acid, and confirmed that this chromophore is in the D configuration for muramic acid. N-Acetylmuramic acid, in which the amino group is replaced by an amido group at C-2, has a c.d. spectrum that is roughly a linear combination of the lactic acid in muramic acid and the amide in 2-acetamido-2-deoxy-D-glucose. This indicates that the amide chromophore and the lactic acid chromophore in N-acetylmuramic acid behave independently. 

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