Aqueous solid-phase peptide synthesis (ASPPS): A novel concept of peptide synthesis (original) (raw)
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European Journal of Organic Chemistry, 2014
A collection of N-triazinylammonium sulfonates, designed according to the concept of "superactive esters", was obtained by treatment of ammonium sulfonates with 2-chloro-4,6-dimethoxy-1,3,5-triazine. The structure of the tertiary amine as well as sulfonate anion influenced their reactivity and stability in N,N-dimethylformamide (DMF) solution. The reagents were successfully used in solution-and solid-phase synthesis of Z-, Boc-, and Fmoc-protected peptides containing natural and unnatural sterically hindered amino acids as
ACS Sustainable Chemistry & Engineering, 2019
mixture (2 × 3 mL each). A solution of Fmoc-Leu-OH (3 equiv), N,N′-diisopropylcarbodiimide (DIC) (3 equiv), and Oxyma Pure (3 equiv) in the proper mixture, preactivated for 5 min, was charged onto the resin and stirred for 1 h. After the peptide coupling, the resin was washed with DMF, DCM and DMF or mixture, iPrOH, and mixture (2 × 3 mL each). Then, 20% piperidine in DMF or selected mixture was charged on the resin (2 × 3 mL × 15 min). The resin was washed and ready for the subsequent couplings, deprotections, and washings, as reported before, to obtain the pentapeptide. The peptide was cleaved from the resin with trifluoroacetic acid (TFA)/H 2 O/ triisopropylsilane (TIS) (95:2.5:2.5) solution for 2 h at room temperature. The crude was directly analyzed by HPLC-MS. Solid-Phase Synthesis of H-D-Phe-Cys-Phe-D-Trp-Lys-Thr-Cys-Thr-ol (Linear Octreotide) in 70:30 Anisole/Dimethyl Carbonate (Method 8). The synthesis was performed in a glass syringe, attached at the bottom to a vacuum source to remove excess of reagents and solvents. The resin (H-Thr(tBu)-ol-2CT-PS 0.6 mmol/g, 500 mg) was washed with 3 mL of Mix C3, 3 mL of iPrOH, and 3 mL of Mix C3. A preactivated solution of Fmoc-Cys(Trt)-OH (3 equiv), DIC (3 equiv), and Oxyma Pure (3 equiv) in Mix C3 (3.3 mL) was charged onto the resin and stirred for 1 h. After the peptide coupling, the resin was washed with 3 mL of Mix C3, 3 mL of iPrOH, and 3 mL of Mix C3. Fmoc removal was performed by adding 2 × 3 mL of 20% piperidine in Mix C3 on the resin, shaking it for 10 min each. After the deprotection, the resin was washed with 4 × 3 mL of Mix C3. The resin was ready for the subsequent couplings, deprotections, and washings, as reported before, to obtain the decapeptide. The final washings were performed with Mix C3 (4 × 3 mL) and iPrOH (3 × 2 mL). The peptide was cleaved from the resin with TFA/TIS/1-dodecanthiol (9 mL/0.7 mL/0.6 mL) solution for 4 h at room temperature. The solution was recovered by filtration. Diisopropyl ether (37 mL) was added dropwise at 0−5°C to the acidic solution until precipitation of peptide was achieved. The resulting mixture was stirred for 1.5 h at 0−5°C. The precipitate was filtered, washed with diisopropyl ether and petroleum ether, and dried under vacuum, affording an off-white solid. The crude was analyzed by HPLC-MS. For the synthesis with method 1, as a substitution for Mix C3 and iPrOH, DMF and DCM were used. Cyclization of Linear Octreotide. Crude trifluoroacetate linear Octreotide (1 g of a raw synthetic product containing 82.3% or 88.0%
An Improved Procedure for N- to C-Directed (Inverse) Solid-Phase Peptide Synthesis
Journal of Combinatorial Chemistry, 2000
A method for solid-phase peptide synthesis in the N-to C-direction that delivers good coupling yields and a low degree of epimerization is reported. The optimized method involves the coupling, without preactivation, of the resin-bound C-terminal amino acid with excess amounts of amino acid tri-tert-butoxysilyl (Sil) esters, using HATU as coupling reagent and 2,4,6-trimethylpyridine (TMP, collidine) as a base. For the amino acids investigated, the degree of epimerization was typically 5%, except for Ser(t-Bu) which was more easily epimerized (ca. 20%). Five tripeptides (AA 1 -AA 2 -AA 3 ) with different properties were used as representative model peptides in the development of the synthetic method: Asp-Leu-Glu, Leu-Ala-Phe, Glu-Asp-Val, Asp-Ser-Ile, and Asp-D-Glu-Leu. The study used different combinations of HATU and TBTU as activating agents, N,N-diisopropylethylamine (DIEA) and TMP as bases, DMF and dichloromethane as solvents, and cupric chloride as an epimerization suppressant. The epimerization of AA 2 in the coupling of AA 3 was further reduced in the presence of cupric chloride. However, the use of this reagent also resulted in a decrease in loading onto the resin and significant cleavage between AA 1 and AA 2 . Experiments indicated that the observed suppressing effect of cupric chloride on epimerization in the present system merely seemed to be a result of a base-induced cleavage of the oxazolone system, the key intermediate in the epimerization process. Consequently, the cleavages were most pronounced in slow couplings. An improved synthesis of fully characterized amino acid tri-tert-butoxysilyl (Sil) ester hydrochloride building blocks is presented. The amino acid Sil esters were found to be stable as hydrochlorides but not as free bases. Although only a few peptides have been used in this study, we believe that the facile procedure devised herein should provide an attractive alternative for the solid-phase synthesis of short (six residues or less) C-terminally modified peptides, e.g., in library format.
Helvetica Chimica Acta, 2012
Dedicated to Prof. Dieter Seebach on the occasion of his 75th birthday The enantioselective condensing reagent 4,6-dimethoxy-1,3,5-triazine (DMT)/strychnine/BF À 4 was obtained by treatment of 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) with strychnine tetrafluoroborate. The reagent was useful under typical conditions of solid-phase peptide synthesis (SPPS) with enantiomerically homogeneous substrates. By SPPS, desired dipeptides were obtained in 84-94% yield using 4 equiv. of racemic Fmoc-Ala, Fmoc-Phe, and/or Fmoc-Tyr for 1 equiv. of Wang resin loaded with Gly, Ala, Leu, Phe, Glu(t Bu), and/or Pro, respectively. For all three Fmoc-protected amino acids, the configuration of the enantiomer preferred under SPPS conditions was independent of the structure of the acylated component and identical to that established in condensations proceeding in solution. In all cases, the enantiomer ratios l/d (er) were in a similar range, and varied from 9 : 92 to 2 : 98 for alanine, and from 90 : 10 to 100 : 0 for aromatic amino acids. The synthesis of Ac-l-Lys(Ac)-d-Ala-d-Ala-OH from racemic Fmoc-Ala gave an l/d ratio of 10 : 90 for the esterification of Wang resin, and 0 : 100 for the formation of peptide bonds.
Solid-phase peptide synthesis using Nα-trityl-amino acids
Letters in Peptide Science, 2001
The preparation of N α -trityl-amino acids is described. Several derivatives of trifunctional amino acids carrying acid-and base-labile side-chain protecting groups and the trityl group at the N α position are prepared for first time. The incorporation of N α -trityl-amino acids into peptide sequences using solid-phase protocols was achieved. The use of the trityl group for the protection of the α-amino group in conjunction with base-labile side-chain protecting groups constitutes a new method for the assembly of peptides in mild conditions.
Solid-phase peptide synthesis using N-alpha-trityl-amino acids
Letters in Peptide Science
The preparation of N α -trityl-amino acids is described. Several derivatives of trifunctional amino acids carrying acid-and base-labile side-chain protecting groups and the trityl group at the N α position are prepared for first time. The incorporation of N α -trityl-amino acids into peptide sequences using solid-phase protocols was achieved. The use of the trityl group for the protection of the α-amino group in conjunction with base-labile side-chain protecting groups constitutes a new method for the assembly of peptides in mild conditions.
Molecules
The growing applications of peptide-based therapeutics require the development of efficient protocols from the perspective of an industrial scale-up. T3P® (cyclic propylphosphonic anhydride) promotes amidation in the solution-phase through a biomimetic approach, similar to the activation of carboxylic moiety catalyzed by ATP-grasp enzymes in metabolic pathways. The T3P® induced coupling reaction was applied in this study to the solution-phase peptide synthesis (SolPPS). Peptide bond formation occurred in a few minutes with high efficiency and no epimerization, generating water-soluble by-products, both using N-Boc or N-Fmoc amino acids. The optimized protocol, which was successfully applied to the iterative synthesis of a pentapeptide, also allowed for a decrease in the solvent volume, thus improving process sustainability. The protocol was finally extended to the liquid-phase peptide synthesis (LPPS), where the isolation of the peptide was performed using precipitation, thus also s...
Amino Acids, 2013
A simple and efficient one-pot procedure that enables rapid access to orthogonally protected N,N 0-diaminoalkylated basic amino acid building blocks fully compatible with standard Boc and Fmoc solid-phase peptide synthesis is reported. Described synthetic approach includes double reductive alkylation of N a-protected diamino acids with N-protected amino aldehydes in the presence of sodium cyanoborohydride. This approach allows preparation of symmetrical, as well as unsymmetrical, basic amino acid derivatives with branched side-chains that can be further modified, enhancing their synthetic utility. The suitability of the synthesized branched basic amino acid building blocks for use in standard solid-phase peptide synthesis has been demonstrated by synthesis of an indolicidin analogue in which the lysine residue was substituted with the synthetic derivative N a-(9H-fluorenyl-9-methoxycarbonyl)-N b ,N b0-bis[2-(tert-butoxycarbonylamino)ethyl]-L-2,3-diaminopropionic acid. This substitution resulted in an analogue with more ordered secondary structure in 2,2,2-trifluoroethanol and enhanced antibacterial activity without altering hemolytic activity. Keywords N-alkylation Á Reductive amination Á One-pot procedure Á Branched basic amino acids Á Solid-phase peptide synthesis Á Indolicidin
Solid-phase synthesis of C-terminal modified peptides
Biopolymers, 2003
In this paper, a straightforward and generic protocol is presented to label the C-terminus of a peptide with any desired moiety that is functionalized with a primary amine. Amine-functional molecules included are polymers (useful for hybrid polymers), long alkyl chains (used in peptide amphiphiles and stabilization of peptides), propargyl amine and azido propyl-amine (desirable for 'click' chemistry), dansyl amine (fluorescent labeling of peptides) and crown ethers (peptide switches/hybrids). In the first part of the procedure, the primary amine is attached to an aldehyde-functional resin via reductive amination. To the secondary amine that is produced, an amino acid sequence is coupled via a standard solid-phase peptide synthesis protocol. Since one procedure can be applied for any given amine-functional moiety, a robust method for C-terminal peptide labeling is obtained.