Dipeptides Phe-Ala

The fundamental problem in the synthesis of peptides is that amino acids must be connected in a defined sequence by specifically forming a peptide bond between the carboxylic acid group of one amino acid and the amino group of another. The potential difficulties arising in such endeavors may be illustrated by considering the synthesis of the simple dipeptide Ala-Phe from the individual amino acids L-alanine (Ala) (3) and L-phenylalanine (Phe) (4), as seen in Equation 24.2. Formation of peptide bonds in a random manner could lead to four different dipeptides. This mixture arises because the carboxylic acid of Ala may react with either the amino... 

Consult with your instructor before performing this experiment, in which you will prepare the dipeptide L-alanyl-L-phenylalanine by hydrolysis of the methyl ester of the monoprotected dipeptide Ala-Phe-OMe (11). The ester may be hydrolyzed in either aqueous base or acid and you should design procedures for both. You should oonsider the ohemical and physical properties of 11 and develop a reaction and a work-up prooedure that will most easily enable you to isolate the product. Obtain the IR, H, and NMR spectra of the purified product for characterization and compare these with the literature data. 

Amino acids used include Gly, Ala, Phe, Leu, His, co-aminoheptanoic acid, and Ala-His dipeptide. It was found that not only single amino acids were added to the dextran, but also poly(amino acid) chains formed during the reaction. 

Dipeptides (gly-leu, ala-phe, leu-gly, ala-val)—Prepare 25 glass test tubes (13 X 100 mm) and 25 microcentrifuge tubes each containing 2 mg of one of the dipeptides. Number each of the tubes in matching sets. Keep a record of the students names and their unknown numbers. Any dipeptide can be used, provided that cysteine, tryptophan, arginine, glutamine, and asparagine are not present. 

AF (= Ala-Phe) (dipeptide) Triticum aestivum (wheat) (Poaceae) [wheatgerm proteolytic hydrolysate] ACE (15)... 

The unique sensitivity of the Phe-Met bond has aroused interest. The dipeptide, H-Phe-Met-OH, is not hydrolyzed nor are tri- or tetrapeptides containing a Phe-Met bond. However, this bond is hydrolyzed in the penta-peptide, H-Ser-Leu-Phe-Met-Ala-OMe (Hill, 1968,1969) and reversing the positions of serine and leucine in this pentapeptide, to give the correct sequence for K-casein, increases the susceptibility of the Phe-Met bond to... 

Thurst S, Koksche B (2003) Protease-catalysed peptide synthesis for the site specific incorporation of alpha-fluoroalkyl amino acids into peptides. J Org Chem 68 2290-2296 Trusek-Holownia A (2003) Synthesis of Z-Ala-Phe.OMe, the precursor of bitter dipeptide in the two-phase ethyl acetate-water system catalysed by thermolysin. J Biotechnol 102 153-163 Tuchscherer G, Mutter M (1996) Template assisted protein de novo design. Pure Appl Chem 68(11) 2153-2162... 

Figure 13 Scatchard plots of data obtained by rebinding peptides to a polymer prepared using His-Ala as the template peptide (a) template dipeptide His-Ala, (b) dipeptide His-Phe, and (c) tripeptide His-Ala-Phe.

Phe dipeptide or Tyr-Ala-Phe tripeptide led to formation of cyclic dipeptides, appropriate diketopiperazines [190,191]. 

Figure 7.5 Two-dimensional LDA score plot for the dipeptide analytes Gly—Ala, Val-Phe, Ala-Phe, Phe-Ala, and D-Phe—Ala. The five different peptides can cleariy be distinguished.

To convert the diprotected dipeptide Boc-Ala-Phe-OMe (10) into Ala-Phe, it is necessary to remove the protecting groups from the nitrogen atom of the N-terminal L-alanine and the carboxylic acid of the C-terminal L-phenylalanine. This might be accomplished by hydrolysis of both groups under acidic conditions. However, the zwitterionic Ala-Phe is difficult to isolate, so in this experiment you will only selectively remove the Boc group from the L-alanine residue to give... 

Starting with the monoprotected dipeptide 11 and the unprotected amino acid L-valine, outline a sequence of reactions for the preparation of the monoprotected tripeptide Val-Ala-Phe. 

Fig. 1 Selected IR/UV spectra of isolated peptides, hydrates and clusters in various spectral ranges. Far-IR (a) conformer X of the Ac-Phe-NH2 monohydrate [51] amide I and II. (b) Ac-Ala-Phe-NH-Me dipeptide (adapted from [52] with permission of AIP), amide A NH stretch region, (c) Ac-Phe-NH2 H2O (X) (adapted from [53] with the permission of ACS), (d) Gramicidin S (adapted from [54] with the permission of Wiley), (e) H-Trp-OH (methanol) clusters. Adapted from [55] with the permission of ACS...

Streptococcal peptides Enantiomeric dipeptides, Tiy- Dy. Ala-Ala, Phe-Phe, Tyr-Tyr, Lys-Ala, Asp-Ala (synthesized) Bovine serum-albumin, bovine y-globulin, o-chyrootrypsin, cytochrome c, bemo obin, lysozyme, myoglobin, ovalbumin, ovomucoid, pepsin, ribonuclease, thyroglobulin, trypsin (SephadexG-100,G-200) Ornithine carbamoylphosphate transferase (Sephadex G-200, G-200 superfiiK)... 

---