Convergent solid phase peptide synthesis. v. synthesis of the 1-4, 32-34, and 53-59 protected segments of the toxin ii of androctonus australis hector.

Two protected peptide segments corresponding to the sequence 32-34 and 53-59 of toxin II of the north African scorpion Androctonus australis Hector have been synthesized on a photolabile Nbb-resin using the TFA-labile Boc -amino protection and HF-labile side chain protecting groups. A third protected peptide corresponding to segment 1-4 has been synthesized on the same resin but with a t-butyl group for β protection of aspartic acid and a Z group on the lysine side chain. For this last segment a combination of Boc and Fmoc groups for -amino protection has been used successfully on the Nbb-resin. After photolysis the crude peptides have been treated by solvent extraction and semi-preparative HPLC to yield highly purified segments. These syntheses show the flexibility of the convergent solid phase approach and how segments with different and independent protecting groups can be assembled by solid phase peptide procedure.     

Convergent solid phase peptide synthesis-III : Synthesis of the 44-52 protected segment of the toxin II of androctonus australis hector

The synthesis of the fully protected peptideBoc-Asn-Ala-Cys(Acm)-Tyr(cHex)-Cys(Acm)-Tyr(cHex)-Lys(Z)-Leu-Pro-OHwhich corresponds to the 44–52 sequence of the Androctonus australis Hector toxin II is described. The synthesis has been carried out on a bromomethyl-Nbb-resin which provides a photolabile anchorage of the peptide. The experimental conditions of the photolysis reaction are very critical in order to obtain satisfactory cleavage yields. The influence of the solvent in this reaction is discussed taking into account the swelling properties of different solvent mixtures and the formation coloured side-reaction products Finally, dimethylformamide/water precipitation followed by reverse phase HPLC is shown to be a very convenient approach to the purification of fully protected peptides.     

Convergent solid phase peptide synthesis IV. : Synthesis of the 35–43 and 32–34 protected segments of the toxin II of androctonus australis hector

The protected peptide segments corresponding to the sequences 35–43 and 32–34 of toxin II of the scorpion Androctonus australis Hector have been synthesized on a -alkoxybenzyl ester resin using the base-labile Fmoc -amino protection and HF-labile side chain protecting groups. Crude peptides obtained after trifluoroacetic acid cleavage have been purified by solvent extraction, dimethylacetamide-water precipitation and semi-preparative reversed phase HPLC. Both synthetic and purification protocols have been optimized for good yields and high purity. Fast atom bombardment mass spectrometry has proved to be a very useful technique to characterize protected peptide segments.     

Convergent solid phase peptide synthesis. I. Synthesis of protected segments on a hydroxymethylphenyloxymethyl resin using the base labile FMOC α-amine protection. Model synthesis of LHRH.

Convergent solid phase peptide synthesis has been applied to yield LHRH. The segments 1–6 and 7–10 of LHRH were synthesized on a hydroxymethylphenyloxymethyl resin using the base labile Fmoc protecting group on the α-amines. The side chains were protected by HF labile groups. Purification of the segments was performed on Sephadex LH-20 columns and by HPLC on Silica Gel 60 columns. The two segments were then assembled on an α-aminobenzyl resin to yield entire sequence of LHRH. After HF treatment and standard purification on Sephadex G-15 and carboxymethylcellulose CM-52 the desired LHRH was obtained. Synthesis of the segments by the same strategy on carbazoyloxymethylphenyloxymethyl resin showed up unexpected difficulties.     

Efficient enantioselective synthesis of orthogonally protected (R)-α-alkylserines compatible with the solid phase peptide synthesis

The Schöllkopf methodology for the asymmetric synthesis of α-amino acids, which was previously not applicable to the construction of quaternary α-amino acids, has been rendered not only suitable but also practical for this purpose and applied to a highly efficient enantioselective synthesis of orthogonally protected (R)-α-alkylserines suitable for the solid phase synthesis.     

Convergent solid phase peptide synthesis. II. Synthesis of the 1–6 apamin protected segment on a NBB-resin. Synthesis of apamin

The article deals with the use of the NBB-resin for synthesis of protected segments followed by solid phase segment condenstaion. Solid phse synthesis on a NBB-resin of the segment 1–6 of apamin yielded either the (1–6) apamin-OH segment after photolysis or (1–6) apamin-NH-NH₂ after hydrazinolysis. The two protected segments were purified on Sephaex LH-20 followed by Bio-Beads S-X1 chromatography and respectively coupled onto a resin on which the 7–18 sequence of apamin was assembled stepwise with the standard solid phase procedure. On a portion of the resin, stepwise synthesis was continued to complete apamin. After HF treatment, deprotection of the cysteines, formation of the disulfide bonds and purification, biologically active apamin was obtained in the three cases.     

An improved procedure for the preparation of aminomethyl polystyrene resin and its use in solid phase (peptide) synthesis

2-Aminoethanol was used to successively replace hydrazine in the preparation of aminomethyl polystyrene resin thereby facilitating purification and by-product removal. The syntheses of the polypeptides ACP (65-74) and oxytocin demonstrated that the use of aminomethyl polystyrene resin prepared in this manner was equal to or better than that prepared using the hydrazine method.