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Relevant academic research and scientific papers

Oxybenzotriazole free peptide coupling reagents for N-methylated amino acids

The main product of N-methylated amino acid coupling, when oxybenzotriazole is present in the reagent (BOP, PyBOP, HBPyU) or as an additive (DCC/HOBt), is the weakly reactive benzotriazolyl ester. On the other hand, the corresponding new halogenated reage

2-Mercaptopyridine-1-oxide-based peptide coupling reagents

The thiouronium salts S-(1-oxido-2-pyridinyl)-1,1,3,3-tetramethylthiouronium hexafluorophosphate (HOTT) and tetrafluoroborate (TOTT), and S-(1-oxido-2-pyridinyl)-1,3-dimethyl-1,3-trimethylenethiouronium hexafluorophosphate (HODT) and tetrafluoroborate (TODT), prepared from 2-mercaptopyridine-1-oxide and 1,1,3,3-tetramethylurea (TMU) or 1,3-dimethylpropyleneurea (DMPU), have been employed as reagents in solution and solid-phase peptide coupling chemistry. Furthermore, 2-mercaptopyridine-1-oxide has been employed as racemization-reducing additive combined with the new thiouronium salts and other frequently used peptide coupling reagents such as DCC or TBTU.

Coupling N-Methylated Amino Acids Using PyBroP and PyCloP Halogenophosphonium Salts: Mechanism and Fields of Application

PyBroP (1) and PyCloP (2), two halotripyrrolidinophosphonium hexafluorophosphates, are peptidecoupling reagents highly efficient for coupling N-methylated amino esters, in contrast with PyBOP (3), the hydroxybenzotriazolyl analogue.These halogenophosphonium salts 1 and 2 are convenient (one-pot reactions) stable solids soluble in conventional solvents.Use of them gave an excellent peptide yield with essentially no epimerization.Activation with these reagents probably involves the formation of an (acyloxy)phosphonium, as shown in the case of 2,4,6-trimethylbenzoic acid activation.In the case of reagents 1 and 2, oxazolone and/or a symmetrical anhydride were intermediates which were rapidly aminolyzed.In contrast, the benzotriazolyl ester intermediate which was formed with PyBOP (3) was poorly reactive with N-methylated amino esters.PyBroP (1) and PyCloP (2) were less efficient in the coupling of some Boc-amino acids because of N-carboxyanhydride formation; this was particularly the case when Boc-Val-OH or Boc-MeVal-OH was coupled with MeVal-OMe.

Polymer-bound N-hydroxysuccinimide as a solid-supported additive for DCC-mediated peptide synthesis

Polymer-supported N-hydroxysuccinimide (P-HOSu) has been prepared from a styrene/maleic anhydride co-polymer and used as an easily removable activating and racemization-reducing additive for the peptide coupling of amino acid derivatives using DCC.

Polymer-bound TBTU as a new solid-supported reagent for peptide synthesis

A new polymer-supported TBTU (P-TBTU) has been prepared from polystyrene-bound 1-hydroxybenzotriazole (P-HOBT) and used efficiently as a solid-supported reagent for peptide-coupling reactions, and is even effective with wet solvents. The P-HOBT can be rec

Convergent synthesis of dolastatin 15 by solid phase coupling of an N- methylamino acid

Convergent synthesis of dolastatin 15 (1), a cytostatic depsipeptide isolated from the Indian Ocean sea hare, has been described. For construction of the backbone, a single-step condensation of peptide fragment 2 and pyrrolidone fragment 3 was successfull

CF3-BOP, CF3-PyBOP and CF3-HBTU: New peptide coupling reagents specially suited for α-aminoisobutyric acid condensations

The peptide-coupling reagents CF3-BOP (1b), CF3-PyBOP (1c) and CF3-HBTU (2a) with built-in 1-hydroxy-6-(trifluoromethyl)benzotriazole proved to be highly efficient for the coupling of α-aminoisobutyric acid residues.

BroP: A new reagent for coupling N-methylated amino acids

BroP (bromo tris(dimethylamino) phosphonium hexafluorophosphate) is a particularly suitable reagent for coupling N-methylated amino acids. It is stable and gives very high yields in short reaction times. Dipeptides are obtained without appreciable epimeri

Amino Acids and Peptides, 63. - Peptide Synthesis via N- or O-Activation of Amino Acids with 1,2-Dihydro-4,6-dimethyl-2-thioxo-3-pyridinecarbonitrile. - Synthesis of the 8-11 Tetrapeptide Sequence of Cyclosporin

Peptides and N-methyl peptides have been prepared in high yields and nearly free of racemisation via N-activation (Scheme 1) or O-activation (Scheme 2) of N-acylamino acids and N-acyl-N-methylamino acids, respectively, by 1,2-dihydro-4,6-dimethyl-2-thioxo