Solid-phase peptide synthesis, general procedure

Automated Stepwise Solid-Phase Peptide Synthesis General Procedure 177-791... 

The major disadvantage of solid-phase peptide synthesis is the fact that ail the by-products attached to the resin can only be removed at the final stages of synthesis. Another problem is the relatively low local concentration of peptide which can be obtained on the polymer, and this limits the turnover of all other educts. Preparation of large quantities (> 1 g) is therefore difficult. Thirdly, the racemization-safe methods for acid activation, e.g. with azides, are too mild (= slow) for solid-phase synthesis. For these reasons the convenient Menifield procedures are quite generally used for syntheses of small peptides, whereas for larger polypeptides many research groups adhere to classic solution methods and purification after each condensation step (F.M. Finn, 1976). 

It is obviously extremely difficult to make generalized statements as to the limitations of any synthetic technique, particularly with one such as solid phase peptide synthesis, where there are so many factors other than Just the success of chain assembly that can affect the overall overcome of the procedure. Nevertheless, it is not unreasonable to expect peptide sequences of up to 50 residues in length to be prepared in moderate to good purity by... 

Linkers, Resins, and General Procedures for Solid-Phase Peptide Synthesis. .. 23... 

Solid-Phase Synthesis of a Reduced Peptide Bond General Procedure 18 ... 

Considering all these features and limitations, it is understandable that currently there is no general procedure available, such as the Fmoc or Boc protocols that are available for nonfunctionalized peptides. However, several approaches have been developed in the last two decades to make lipidated peptides accessible. This chapter describes both the corresponding solution-phase approaches and solid-support approaches for the synthesis of lipidated peptides. In line with the framework sketched above, both the different protecting groups and solid-phase linker systems that have been developed will be reviewed. 

Chemical ligation methods for peptide synthesis using thioester chemistry in solution have been previously documented (see Vol. E 22a, Section 4.1.5). Generalized procedures for solid-phase ligation have been developed that simplify the overall procedure. One method uses a safety-catch acid labile linker at the C-terminus and was used for the synthesis of a 71-amino acid chemokine, vMIP I (Section 5.3.2.1). Another procedure uses a selectively cleavable glycolate ester linkage (Section 5.3.2.2). 

A major advancement in the Fmoc-based solid-phase synthesis of Tyr(P)-peptides was realized with the Fmoc-Tyr[PO(OR1)2]-OH derivatives 7 (R1 = Bzl, tBu, Mdpse) [Mdpse = 2-(methyldiphenylsilyl)ethyl] in which the acid-labile phosphate esters offered simple cleavage by TFA treatment. While the initial difficult synthesis of derivatives 7 restricted general synthetic usage, the subsequent commercial availability of these derivatives and their compatibility with solid-phase synthesis has provided a simple and efficient procedure for the routine synthesis of large complex Tyr(P)-peptides. 

Synthesis of the peptide Ac-A-Bn-C-OH was performed by a stepwise solid-phase fragment condensation approach, as shown in Scheme 3, using the general procedures of the automated solid-phase method. The synthesis began with Boc-C-resin support and continued with the stepwise addition of protected peptide fragments until the completed peptide was assembled on the resin. The supported peptide Ac-A-Bn-C-resin was obtained after deprotection of Boc-A-Bn-C-resin and acetylation of the free amino groups. 

Solid-Phase Synthesis of Dialkyl Peptide-Amphiphiles 12 General Procedure 144-66 ... 

Solid-Phase Synthesis of Monoalkyl Peptide-Amphiphiles 15 General Procedure 64-65 ... 

Besides these specific examples related to peptides of therapeutic importance, similar thematic variations can, in general, be used to (1) assess the purity of natural and synthetic peptides isolated by alternative procedures (2) analyze the crude reaction product mixtures from solution- or solid-phase synthesis, thus allowing deletion or partially deprotected products to be rapidly recognized and the progress of a synthesis to be followed (3) confirm the identity of a peptide by co-chromatpgraphy with... 

Synthesis of the four-helix bundles was accomplished by a two-step procedure (outlined as a flow chart in Figure 2). Proteins were synthesized by solid phase methods in accordance with general principles (62-64) using a peptide synthesizer (model 431, Applied Biosystems (ABI), Foster City, CA). L-con-figuration amino acid derivatives were used (The Peptide Institute, Osaka, Japan). The acid-labile fert-butyloxycarbonyl- (f- Boc)-protecting groups were... 

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