Threonine dipeptide

Peters, D., and J. Peters. 1982a. Quantum Theory of the Structure and Bonding in Proteins Part 15. The threonine dipeptide. J. Mol. Struct. (Theochem) 90, 321-334. 

Access to the imino group of oxazolidine-4-carboxylic acid is even more sterically hindered when substitutions are performed at the C2 position. For such cases, the typical procedure is based on the conversion of the desired serine or threonine dipeptides with unprotected hydroxy groups into the oxazolidine rings by reaction with aldehydes or ketones,1139,1691 as described in Vol. E 22a, Section 2.3.2.4. 

Table 5. Principal Component Analysis of the Free Energies of Serine and Threonine Dipeptides in Methanol at 300 K" ...

Principal component analysis can also be carried out by using simulation data obtained at different conditions, such as at different temperatures, so that more observables can be used to construct a larger sensitivity matrix. This has been done for the evaluation of serine and threonine dipeptides in methano , but the key findings were essentially the same as those described above when the results from only two simulations were used in the analysis. 

Chou et compared Karplus curves parametrized by using experimental V couplings with those derived by best-fitting the results of DFT calculations carried out on conformers of valine and threonine dipeptide analogues. The experimentally parametrized Karplus curves agreed well with the curves obtained from DFT calculations. 

Scheme 1 Phosphinite derivatives of serine, threonine and tyrosine containing dipeptides 1 R = H, Boc-Phe-Ser(OPPh2)OMe 2 R = Me, Boc-Phe-Thr(OPPh2)OMe 3 R = Ph, Boc-Phe-Tyr(OPPh2)OMe 4R = cyhex, Boc-Phe-Tyr(OPcyhex2)OMe.

In NRPS, the cyclization domain catalyzes cyclization of the side-chain nucleophile from a dipeptide moiety such as AA-Ser or AA-Cys (AA = amino acids) to form a tetrahedral intermediate, followed by dehydration to form oxazolines and thiazolines (Scheme 7.1) [20]. The synthesis of a 2-methyl oxazoline from threonine follows a similar mechanism. Once a heterocycle is formed, it can be further modified by reductase to form tetrahydro thiazolidine in the case of pyochelin biosynthesis. Conversely, oxidation of the dehydroheterocycles lead to heteroaro-mahc thiazoles or oxazoles as in the case of epothilone D (Figure 7.2) [21]. 

Scheme 8 Synthesis of a Peptide-Based 5-Methyloxazole from a Dipeptide Containing a Threonine Residue via an Oxidation-Cyclodehydration Sequence 631...

Stereochemically controlled synthesis of this subunit, which contains five stereogenic centers, is important to an efficient bleomycin synthesis. (2S,3S,4i )-4-(/er/-Butoxycarbonyl-amino)-3-hydroxy-2-methylpentanoic acid (15) was obtained via a stereoselective syn aldol addition of a boron Z-enolate with (27 )-2-(tert-butoxycarbonylamino)propanal (Scheme 4). Similarly, the L-threonine subunit 18 was prepared by diastereoselective syn aldol addition of an N- acy I ox azo I i di n one stannous Z-enolate with acetaldehyde. The bithiazole unit 19 was prepared using a direct DCC-promoted condensation of 3-(methylsulfanyl)propylamine. Convergent access to tetrapeptide S was obtained by coupling of acid 15 and deprotected 18 to give dipeptide 20, followed by further coupling with the bithiazole 19 to ultimately give tetrapeptide S (21). 

The synthesis of threonine can be made stereospecific using optically active complexes of the type L-[Co(en)2Gly]2+ but with low asymmetric yield.442 In the case of dipeptide complexes only... 

As Scheme 47 illustrates, the threonine derivative 149 is coupled with 147b to furnish the dipeptide 150, which, after protecting group manipulation and further... 

Based on these results, what two amino acids are present in your unknown dipeptide As shown in Table 6-1, it may be difficult to resolve some PTC-amino acids (PTC-arginine and PTC-threonine). Still, this mobile-phase gradient will resolve the majority of the PTC-amino acid derivatives. How might the conditions of this experiment be changed to resolve molecules such as PTC-arginine and PTC-threonine ... 

Fig. 10 Enzyme-catalyzed dipeptide synthesis with a subsequent threonine - phenylalanine exchange to form a more stable assembly...

Coupling of 15 with D-threonine methyl ester in the presence of PyBroP and DMAP gives the dipeptide 73. The oxazole 74 is formed after Dess-Martin oxidation and cyclodehydration with triphenylphosphine/iodine. After formation of the methylamide function, an iterative sequence of deprotection with TBAF and coupling with 15 leads to the dipeptide 75, then to the tripeptide 76 and finally to the tetrapeptide 77. The coupling reagent is PyBroP in each case. The overall yield (74 —> 77) is 21 %. After cata-... 

As a result of GC-MS analyses, 103 metabolites were determined, of which 66 were successfully identified and 18 were used to create a diagnostic model. Of these 18 metabolites, 5 (suberic acid, glycine, L-tyrosine, L-threonine, and succinic acid) had significantly higher levels in patients with HCC than in healthy volunteers (p < 0.05). Other metabolites (oxalic acid, xylitol, urea, phosphates, propanoic acid, threonine, pimelic acid, butyric acid, trihydroxypentanoic acid, hypoxanthine, arabinofuranose, dipeptide of hydroxyproline, and tetrahydroxypentanoic acid) showed higher levels in healthy volunteers (p < 0.05). In addition, Wu et al. determined the levels of AFP using an ELISA test in serum from the same patients and healthy volunteers as in the metabolomic study of urine samples. An AFP concentration above 20 ng/mL suggests a positive result and the presence of... 

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