Proline, acidity

THF) containing 10% (v/v) of trifluoroacetic acid (TFA). After microwave irradiation for 25 s at 60 °C, the mixture was concentrated to dryness, 5 equivalents each of N,N-diisopropylethy]amine (DIEA) and (S)-proline acid chloride in bdmimPF6/ THF were added, and the resulting mixture was stirred at room temperature for 3 min. Finally, after in situ deprotection with 20% piperidine (v/v) in bdmimPF6/ THF at 60 °C for 1 min in the microwave reactor, the target compounds were obtained as mixtures of diastereomers. 

Our laboratory started to work on circadian rhythms by serendipity, while studying the liver-specific transcription of the serum albumin gene. We isolated a cDN A copy for a transcription factor that we dubbed DBP (for albumin promoter D-element Binding Protein). DBP, a basic leucine zipper (bZip) transcription factor, is the founding member of the PAR (proline-acidic amino acid rich)-domain bZip transcription factors, a small subfamily of bZip proteins consisting of DBP, TEF and HLF. It turned out that DBP protein and mRNA accumulation undergo circadian cycles with amplitudes in excess of one hundred-fold (Wuarin Schibler 1990). 

The reaction of iV-benzyloxycarbonyl L-proline acid chlorides 134 with imine 135 in the presence of triethylamine, at room temperature, gave the corresponding spiro-(3-lactams 136, 137 as a 1 1 mixture of diastereoisomers, which were separated by column chromatography. The Staudinger reaction proceeds with complete stereoselectivity with a cis relative disposition of the pyrrolidine nitrogen and the phenyl group, but no asymmetric induction was observed. However, very... 

An isolated example of Grignard acylation by proline acid chloride was achieved by the use of a large excess of acid chloride (43). The keto aldehyde (45) was obtained in 71% yield (equation 33). Unfortunately, the reaction with stoichiometric amounts of the acid halide were not discussed. In light of the results of Sato and Eberle, the real capabilities of this reaction were apparently not explored. 

This protocol was also applied to diazepam derivatives 6 [49]. When these compounds were treated with N-benzyloxycarbonyl-L-proline acid chloride and tetrahydrofuroyl chloride, the expected spirocyclic systems 7 (Scheme 2) were obtained in good yields. In the case of the N-benzyloxycarbonyl-L-proline acid chloride, the reaction was carried out at room temperature, while the process involving the tetrahydrofuroyl chloride needed to be performed in refluxing toluene. This higher temperature was the likely cause of the loss of selectivity observed in the latter case, in which a 10 1 mixture of diastereoisomers was obtained. 

Variant Glutathione 5-Oxo- proline Acid-base balance Reticulo- cytes ... 

The positions of the three amino-acids are shown clearly by the colour of their zones or spots, the proline being yellow and the glycine and phenylalanine being blue. Note the Rp value for each amino-acid ... 

The synthesis described met some difficulties. D-Valyl-L-prolyl resin was found to undergo intramolecular aminoiysis during the coupling step with DCC. 70< o of the dipeptide was cleaved from the polymer, and the diketopiperazine of D-valyl-L-proline was excreted into solution. The reaction was catalyzed by small amounts of acetic acid and inhibited by a higher concentration (protonation of amine). This side-reaction can be suppressed by adding the DCC prior to the carboxyl component. In this way, the carboxyl component is "consumed immediately to form the DCC adduct and cannot catalyze the cyclization. 

Proline is relatively compact because of the cyclic nature of its side chain It has less conformational flexibility than the other ammo acids and the presence of proline affects the shape of a peptide more than other ammo acids... 

One of the homochiral starting materials (45) for the acetylcholinesterase (ACE) inhibitor captopril [62571 -86-2] (47) is produced by a Hpase enzyme-catalyzed resolution of racemic 3-methyl-4-acetylthiobutyric acid (44) and L-proline (46) (65). 

L-tyrosine D-tyrosine DL-tyrosine Heterogclic proline [60-18 ] [556-02-5] [556-03-6] [7005-20-1 ] Pro 2-pyrrobdine-carboxyb c acid N COOH 115.13... 

The principle of this method depends on the formation of a reversible diastereomeric complex between amino acid enantiomers and chiral addends, by coordination to metal, hydrogen bonding, or ion—ion mutual action, in the presence of metal ion if necessary. L-Proline (60), T.-phenylalanine (61),... 

Thin-Layer Chromatography (tic). Tic (126) is used widely for quahtative analysis and micro-quantity separation of amino acid mixtures. The amino acids detected are developed by ninhydrin coloring, except for proline and hydroxyproline. Isatia has been recommended for specific coloring of pToline (127). 

L-Glutamic acid does not racemize in neutral solution, even at 100°C. Deviation of pH from neutral to greater than 8.5 results in thermal racemization with loss of taste characteristics. Racemization in neutral solution occurs at 190 °C after formation of the lactam, 5-oxo-L-proline, pyroglutamic acid [98-79-3]. 

Fig. 1. The side chain R of the 20 standard amino acids +H3N—CHR—COO at pH 7. For proline, the complete stmcture is shown. Amino acid side chains can be categorized as aUphatic (Gly, Ala, Val, Leu, and He), hydrophilic (Ser, Thr, Asp, Glu, Asn, Gin, Lys, and Arg), sulfur-containing (Cys and...

Fig. 10. Sequences (see Table 1) of betabeUins. In each case, only one-half of the P-sandwich is shown. The dimer is formed from identical monomeric sets of four P-strands. In the pattern sequence, e is for end, p is for polar residue, n is for nonpolar residue, and t and r are for turn residues. Lower case f is iodophenyialanine lower case a, d, k, and p are the D-amino acid forms of alanine, aspartic acid, lysine, and proline, respectively B is P-alanine (2,53,60,61).

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