Kleomenis Barlos

Darstellung Geschützter Peptid-Fragmente unter Einsatz substituierter Triphenylmethyl-Harze

Zusammenfassung Substituted triphenylmethyl(trityl) resins have been tested for their applicability for the synthesis of protected peptide fragments. Among them the 2-chlorotrityl resin 3c fulfills all requirements needed to obtain the desired fragments in high yield and purity, using Fmoc-amino acids protected at their side chains with groups of the t-butyl type.

Veresterung von partiell geschützten peptid-fragmenten mit harzen. Einsatz von 2-chlortritylchlorid zur synthese von Leu15 -gastrin I

Zusammenfassung The esterification of several partially protected peptide fragments through the C-terminal or a free side chain carboxy group with hydroxy groups containing resins and the 2-chlorotritylchloride resin 8 is described. As an application example crude protected Leu 15 - gastrin I ( 15a ) has been obtained in 99% yield by the “solid-phase” method using 8 as the solid support. Crude 15a has been deprotected to free Leu 15 - gastrin ( 16 ) which is thus obtained in 92% yield and 90% purity.

Short-Term Monotherapy in HIV-Infected Patients with a Virus Entry Inhibitor Against the gp41 Fusion Peptide

An optimized derivative of a natural HIV-1 entry inhibitor targeting the gp41 fusion peptide shows antiviral potency and minimal side effects in a Phase I/II clinical trial. Anchors Away: Blocking HIV Entry Combination antiretroviral therapy has been very successful for treating infection with the human immunodeficiency virus (HIV-1), which causes AIDS. However, drug resistance is emerging and there is a need to develop new antiretroviral drugs that work earlier in the virus life cycle, for example, by preventing HIV-1 from entering host cells. Two such virus entry inhibitors, maraviroc and T-20, are in clinical use, but both have drawbacks. Forssmann, Kirchhoff and their colleagues have now developed a new virus entry inhibitor called VIRIP (VIRus-Inhibitory Peptide), a 20-peptide fragment of α1-antitrypsin, an abundant circulating serine protease inhibitor. VIRIP and its optimized derivative VIR-576 are so-called anchoring inhibitors because they prevent the gp41 fusion peptide of HIV-1 from inserting itself into the host cell membrane. This then blocks the next step in the virus life cycle, which is fusion of the virion envelope with the host cell membrane. Forssmann and co-workers now report on a Phase I/II clinical trial in which 18 HIV-1–infected patients who were not on any other antiretroviral therapy were treated for 10 days with three different doses of VIR-576 (0.5, 1.5, 5.0 g/day). They show that VIR-576 reduced the viral load in the plasma of patients on the highest dose by an order of magnitude and that the drug was well tolerated. Previous studies have shown that the gp41 fusion peptide is essential for HIV-1 entry into host cells, and suggest that it may be difficult for HIV-1 to develop resistance to VIR-576 because the fusion peptide is highly conserved and hardly tolerates changes without loss of function. This anchoring inhibitor, unlike other HIV entry inhibitors, is also active against many different HIV strains and has a different target (the gp41 fusion peptide). Thus, VIR-576 represents a potential new class of HIV entry inhibitor. However, VIR-576 does have some drawbacks too. Because VIR-576 is a peptide, it will be costly and time-consuming to produce and it must be administered intravenously. This has prompted Kirchhoff and colleagues to start searching for a small molecule that would block the gp41 fusion peptide in the same way as VIR-576 but would have the advantage that it could be made cheaper and given orally. To infect host cells, most enveloped viruses must insert a hydrophobic fusion peptide into the host cell membrane. Thus, fusion peptides may be valuable targets for developing drugs that block virus entry. We have shown previously that a natural 20-residue fragment of α1-antitrypsin, designated VIRus-Inhibitory Peptide (VIRIP), that binds to the gp41 fusion peptide of HIV-1 prevents the virus from entering target cells in vitro. Here, we examine the efficacy of 10-day monotherapy with the optimized VIR-576 derivative of VIRIP in treatment-naïve, HIV-1–infected individuals with viral RNA loads of ≥10,000 copies per ml. We report that at the highest dose (5.0 grams per day), intravenous infusion of VIR-576 reduced the mean plasma viral load by 1.23 log10 copies per ml without causing severe adverse effects. Our results are proof of concept that fusion peptide inhibitors suppress viral replication in human patients, and offer prospects for the development of a new class of drugs that prevent virus particles from anchoring to and infecting host cells.

9-Fluorenylmethyloxycarbonyl/ tbutyl-based convergent protein synthesis.

Besides linear solid phase peptide synthesis, segment condensation in solution and chemical ligation, convergent peptide synthesis (CPS) was developed in order to enable the efficient preparation of complex peptides and small proteins. According to this synthetic strategy, solid phase synthesized and suitably protected peptide fragments corresponding to the entire peptide/protein-sequence are condensed on a solid support or in solution, to the target protein. This review summarizes CPS performed utilizing the mild 9-fluorenylmethyloxycarbonyl/tbutyloxycarbonyl-based protecting scheme for the amino acids.

A new reagent for the cleavage of fully protected peptides synthesised on 2-chlorotrityl chloride resin

A mixture of hexafluoroisopropanol–dichloromethane (1:4 v/v) acts as a fast, effective and convenient reagent for cleaving protected peptide fragments with a minimal amount of racemization from 2-chlorotrityl chloride resin.

Solid phase synthesis of benzothiazolyl compounds

2-Aminobenzenethiol, bound through its thiol function to the 2-chlorotrityl (Clt)-, trityl (Trt)-, 4-methyltrityl (Mtt)- and 4-methoxytrityl (Mmt)-resins, was acylated at the amino-function by aliphatic and aromatic acids. The obtained 2-N-acyl-aminobenzenethiols were cleaved from the resin by treatment with trifluoroacetic acid solutions in dichloromethane. The 2-N-acyl-aminobenzenethiols released from the resin were cyclised to the corresponding 2-substituted benzothiazoles, by standing in a solution of dithiothreitol in DMF or methanol for 1–3 h at room temperature.

Preparation of MUC-1 oligomers using an improved convergent solid-phase peptide synthesis.

The sequentially repeating nature of the core mucin polypeptide chain MUC-1 on the surface of malignant cells makes it an excellent target for cancer immunotherapy. We describe a reliable and efficient method of synthesizing oligomers, up to five tandem repeats and oligomer heterotope derivatives with a 15-amino acid epitope from tetanus toxin using an improved convergent solid-phase peptide synthesis. The different oligomers were easily distinguishable by reverse-phase high pressure liquid chromatography, but they were poorly fixed and migrated with the same migration rate, irrespective of size, in electrophoretic studies. In contrast, the oligomer heterotopes exhibited size-dependent electrophoretic behavior but in high pressure liquid chromatography chromatograms the different heterotopes were eluted simultaneously in two peaks representing thel- and d-enantiomers of the derivatives. The oligomer heterotopes were recognized as antigens in Western blotting with a murine monoclonal antibody against the epitope APDTR. In enzyme immunoassay studies with the same antibody an increasing reactivity was observed against the larger oligomers and confirmed by inhibition assays as the MUC-1 pentamer was the most efficient inhibitor. These results support the suggestion that the pentamer attains a structure closer to the native conformation and is more immunogenic. In conclusion, large composite peptides can be reliably synthesized with the convergent solid-phase peptide strategy offering an attractive option to vaccine designing and development.

Application of 2-chlorotrityl chloride in convergent peptide synthesis

Abstract Fmoc/tBu-protected peptides, synthesized on 2-chlorotrityl resin (CLTR), have been quantitatively esterified by treatment with 2-chlorotrityl chloride (Clt-chloride) and diisopropylethylamine (DIPEA). The obtained peptide Clt-esters have been deprotected at the Nα-function and subsequently condensed in solution to larger peptides. The Clt-function of the obtained products could be selectively removed by treatment with acetic acid.

Resin-bound aminothiols: synthesis and application

Abstract Aminothiols were attached through their thiol group onto the 4,4′-dimethoxytrityl (Dmt)-, 4-methoxytrityl (Mmt)-, 4-methyltrityl (Mtt)-, trityl (Trt)- and 2-chlorotrityl (Clt)-resins. The new resins were used in the solid-phase synthesis of aminothiol containing peptides utilizing N -Fmoc amino acids. The synthesized peptides were cleaved from the resins by treatment with trifluoroacetic acid (TFA) solutions using triethylsilane (TES) or ethanedithiol (EDT) as scavengers.

Darstellung und einsatz von N-Fmoc-O-Trt-hydroxyaminosäuren zur “solid phase” synthese von peptiden

Zusammenfassung The preparation of the N-Fmoc-O-Trt derivatives of serine, threonine and tyrosine is described. Their usefulness in peptide synthesis has been determined in the successful solid phase preparation of the partially protected ACTH (fragment 1–10) and peptide T 12 . The latter, having six hydroxy amino acid side chains protected with Trt groups, can be quantitatively cleaved from the applied 2-chlorotrityl resin with simultaneous side chain deprotection.