Peptide synthesis with

For a review of peptide synthesis with dicyclohexylcarbodiimide and other coupling agents, see Klausner, Y.S. Bodansky, M. Synthesis, 1972, 453. 

Application of amino acid silyl esters or A-silyl amino acid silyl esters as amino components is very convenient in peptide synthesis with CDI, because the resulting peptide silyl esters are easily hydrolyzed to dipeptides during the usual work up. They need not be saponified in a separate step, as would be the case with the corresponding alkyl esters. Furthermore, no racemization occurs with this method.tl8],tl9]... 

F Weygand, P Huber, K Weiss. Peptide synthesis with symmetrical anhydrides I. Z Naturforsch 22B, 1084, 1967. 

H Hagenmeier, H Frank. Increased coupling yields in solid phase peptide synthesis with a modified carbodiimide coupling procedure. Hoppe-Seyler s Z Physiol Chem 353, 1973, 1972. 

HC Beyerman, J Hirt, P Kranenburg, JLM Syrier, A van Zon. Excess mixed anhydride peptide synthesis with histidine derivatives. Rec Trav Chim Pays-Bas 93, 256, 1974. 

DS Kemp, S-W Wang, J Rebek, RC Mollan, C Banquer, G Subramanyam. Peptide synthesis with benzisoxazolium salts-II. Activation chemistry of 2-ethyl-7-hydroxy-benzisoxazolium fluoroborate coupling chemistry of 3-acyloxy-2-hydroxy-V-ethyl-benzamides. Tetrahedron 30, 3955, 1974. 

JK Inman. Peptide synthesis with minimal protection of side-chain functions, in The Peptides Analysis, Synthesis, Biology, Vol. 3, pp 253-302, Academic Press, New York, 1981. 

The acylated peptides (Myr)GCX-Bimane 31 a-e (X = G, L, R, T, V), which are found in certain nonreceptor tyrosine kinases and ct-subunits of several heterotrimeric G-proteins, were synthesized in solution using common solution-phase peptide synthesis with X-myristoylglycine as a building block. These model peptides were used for acylation studies with palmitoyl-CoA in phospholipid vesicles at physiological pH. For such uncatalyzed spontaneous reactions only a modest molar excess of acyl donor species (2.5 1) was necessary. Unprotected side chains of threonine or serine are not interfering with this S-acylation (Scheme 14). 

As discussed above, proteases are peptide bond hydrolases and act as catalysts in this reaction. Consequently, as catalysts they also have the potential to catalyze the reverse reaction, the formation of a peptide bond. Peptide synthesis with proteases can occur via one of two routes either in an equilibrium controlled or a kinetically controlled manner 60). In the kinetically controlled process, the enzyme acts as a transferase. The protease catalyzes the transfer of an acyl group to a nucleophile. This requires an activated substrate preferably in the form of an ester and a protected P carboxyl group. This process occurs through an acyl covalent intermediate. Hence, for kineticmly controlled reactions the eii me must go through an acyl intermediate in its mechanism and thus only serine and cysteine proteases are of use. In equilibrium controlled synthesis, the enzyme serves omy to expedite the rate at which the equilibrium is reached, however, the position of the equilibrium is unaffected by the protease. 

T. Michei, B. Koksch, S.N. Osipov, A.N. Golubev, J. Sieler, K. Burger, Peptide synthesis with a-(difluoromethyl)-substituted ot-amino acids. Coll. Czech. Chem. Commun. 67(10) (2002) 1533-1559. 

Side Products in Peptide Synthesis with Cystine Derivatives... 

Peptide Synthesis with S-Famesylated Cysteine Derivatives and Cysteine... 

Celovsky, V. and Bordusa, F. (2000). Protease-catalyzed fragment condensation via substrate mimetic strategy a useful combination of solid-phase peptide synthesis with enzymatic methods. /. Pept. Res., 55, 325-9. 

The optimum yield of a condensation product is obtained at the pH where Ka has a maximum. For peptide synthesis with serine proteases this coincides with the pH where the enzyme kinetic properties have their maxima. For the synthesis of penicillins with penicillin amidase, or esters with serine proteases or esterases, the pH of maximum product yield is much lower than the pH optimum of the enzymes. For penicillin amidase the pH stability is also markedly reduced at pH 4-5. Thus, in these cases, thermodynamically controlled processes for the synthesis of the condensation products are not favorable. When these enzymes are used as catalysts in thermodynamically controlled hydrolysis reactions an increase in pH increases the product yield. Penicilhn hydrolysis is generally carried out at pH about 8.0, where the enzyme has its optimum. At this pH the equiUbrium yield of hydrolysis product is about 97%. It could be further increased by increasing the pH. Due to the limited stability of the enzyme and the product 6-aminopenicillanic acid at pH>8, a higher pH is not used in the biotechnological process. 

Because no treatment with acid is required during peptide assembly, peptide synthesis with Fmoc amino acids can be conducted on acid-sensitive supports (e.g. Tenta-gel) and with acid-labile linkers. Wang resin is suitable for most purposes, but other supports, such as Sasrin or 2-chlorotrityl resin, can also be used. CPG, macroporous... 

Acyl chlorides. Acyl chlorides are formed rapidly by reaction of carboxylic acids with SOCl2 and pyridine in CH2C12 at 25°. The dicyclohexylammonium salts of carboxylic acids react particularly rapidly (ca. 1 minute). The acid chlorides prepared in situ in this way react with amines in the presence of DMAP or DBU to form amides in >85% yield. This SOCl2-Py method is also useful for peptide synthesis with slight racemization. 

More recent advances in the synthesis of head-to-tail cyclic peptides combine solid-phase peptide synthesis with solid-phase cyclization reactions whilst the peptide is still attached to the resin. 25 Such methods have obvious merits as they reduce manipulation of the peptides in solution. The method typically requires a suitable side-chain functional group... 

Table 7 Enzymatic Peptide Synthesis With ACV Synthetase... 

A typical coupling cycle for peptide synthesis with Boc-amino acids on a peptide synthesizer (Beckman Model 990) was as follows ... 

Scheme 6.1.4. Reverse (N —> C) directed solid-phase peptide synthesis with the 2-chlorotrityl resin.

Sheehan and another Nobel laureate Khorana showed independently that the mild carbodiimide mediated synthesis is very useful in the condensation reaction of N-blocked amino acids with a different amino acid to form a peptide bond. The O-blocking of carboxylic acid groups in peptide synthesis with amino nucleophiles, such as glycine esters or amides, " or novel silicon containing protective groups is also mediated by carbodiimides. Likewise, alcohols are protected with 4-benzyloxybutyric acid, using EDC/DMPA. ... 

Kearney, T. and Giles, J. (1989) Fmoc peptide synthesis with a continuous flow synthesizer. Amer. Biotechnol. Lab. 7, 34-44. 

Similarly, carbonylimidazolinm salts have been introduced. For example, CBMIT 15 is described as an efficient amino acylating reagent for peptide synthesis with sterically hindered amino acids (36). 

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