Pyroglutamic acid structure

Fig. 13. Primary structures in the family of tachykinins Pyr = pyroglutamic acid...

Figure 1 Examples of insect and crustacean neuropeptides of similar structure with the same or different functions. Pandanus borealis is a shrimp. pGlu, pyroglutamic acid.

It was of interest to examine the use of chiral bi-2-naphthol to resolve the racemic amino alcohol 11 that can be prepared starting from pyroglutamic acid (Scheme 9). Preliminary studies revealed that die resolution can be readily carried out using B(OH)] and chiral bi-2-naphthol (Scheme 9).17 Further optimisation of the results and structural analysis of the borate complex involved in this reaction are under way. 

A substantial proportion of biologically active peptides carry an acylated A-terminus or A-terminal pyroglutamic acid and are therefore not amenable to chemical degradation from the A-terminus (Edman sequence analysis). However, these A-blocked peptides and A-protected peptides, prepared through laboratory peptide synthesis for which one needs routine checks on structure, can be studied by MS. 

Glp refers to a modified form of glutamic acid, pyroglutamic, whose structure is shown in Table 5. 

Moreover, RA-IX (155) and RA-X (156) were also included in this RA-series. Their structures were determined by spectroscopic and chemical methods. RA-IX contained a pyroglutamic acid instead of the Ala-2 found in RA-VII, and RA-X had glutamic acid instead of Ala-2. RA-XI (157) was similar to RA-X having a glutamic acid moiety. Recently, RA-XII (158) - XVI (162) have been isolated as glucosides from the same plant (Fig. 17) [80-83]-... 

Pyroglutamic acid was used as the starting material in a synthesis of (+)-ipalbidine, an analgesic alkaloid obtained from the seeds of the white moonflower, Ipomoea alba. No bonds are made or broken to the chirality center of (5)-pyroglutamic acid in this synthesis. Which of the following is the structure of (+)-ipalbidine ... 

Fig. 4A,B. Gas chromatography - mass spectroscopy of the acid hydrolysate of the stored material. A The ion chromatogram of a 2 N HCl hydrolysate with the inset depicting the fragmentation pattern and structure of the glutamic acid derivative. B The spectrum and structure of pyroglutamic acid seen in a 0.5 N HCl hydrolysate. (From [24] with permission)...

Syntheses for all but the feline peptide have been reported. All are 17-residue peptides having the amino end blocked by a pyrrolidone carboxylic acid (PCA, pyroglutamic acid) residue, and the carboxyl group blocked as the amide. The structures of these peptides, which differ by no more than two amino acids, are shown below K... 

Fig. 14. Structure of gephyrotoxin. The absolute configuration is based on x-ray analysis of hydrobromide and is depicted on the right (86). The natural compound is the 1-enantiomer (107). It is, therefore, inexplicable that synthesis from L-pyroglutamic acid (107) of the enantiomeric configuration revealed by x-ray analysis should yield the d-enantiomer. Fujimoto and Kism (107) proposed that the true configuration of natural gephyrotoxin must be opposite to that revealed by x-ray analysis. The x-ray analysis was done on gephyrotoxin isolated from the same population of frogs as the material shown by optical rotation measurements to be the levorotatory enantiomer. However, the two samples of gephyrotoxin were from extracts obtained in different years...

Fig. 5. Primary structure and site of phosphorylation of k-CN A-1P, and the site of cleavage by chymosin (V). The N-terminal amino acid is pyroglutamate (Eigel et al., 1984 Thompson et al., 1985).

Previous papers have investigated the suitable use of xylan in papermaking [10] and textile printing [21]. In the drug delivery field, xylan extracted from birch wood has been used for the production of nanoparticles after structural modification by the addition of different ester moieties, namely those with furoate and pyroglutamate functions [21]. On the other hand, the esterification of xylan from beech wood via the activation of the carboxylic acid with iV,iV -carbonyldiimidazole has been carried out in order to produce prodrugs for ibuprofen release [10, 21, 22, 37]. 

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