- CF3-NO2-PyBOP: A New and Highly Efficient Coupling reagent for N-Methyl Amino Acids
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1-hydroxy-4-nitro-6-(trifluoromethyl)benzotriazole-containing phosphonium salt CF3-NO2-PyBOP (1h) proved to be a powerful reagent for in situ coupling of N-methylated amino acids.
- Wijkmans, J.C.H.M.,Blok, F.A.A.,Marel, G.A. van der,Boom, J.H. van,Bloemhoff, W.
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- Convergent synthesis of dolastatin 15 by solid phase coupling of an N- methylamino acid
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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
- Akaji, Kenichi,Hayashi, Yuzo,Kiso, Yoshiaki,Kuriyama, Naohiro
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p. 405 - 411
(2007/10/03)
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- Coupling N-Methylated Amino Acids Using PyBroP and PyCloP Halogenophosphonium Salts: Mechanism and Fields of Application
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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.
- Coste, Jacques,Frerot, Eric,Jouin, Patrick
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p. 2437 - 2446
(2007/10/02)
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- CF3-BOP, CF3-PyBOP and CF3-HBTU: New peptide coupling reagents specially suited for α-aminoisobutyric acid condensations
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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.
- Wijkmans, Jac C. H. M.,Kruijtzer, John A. W.,Marel, Gijs A. van der,Boom, Jacques H. van,Bloemhoff, Wim
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p. 394 - 397
(2007/10/02)
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- N-methyl N-carboxyanhydride: An unexpected by-product when coupling boc-n-methyl amino acids
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Activation of Boc-amino acids and Boc-N-methyl amino acids leads to the corresponding NCA. This side reaction explains the low yields obtained when coupling N-methyl amino acids. It was not observed with the Z-or Fmoc-protective groups.
- Frerot, Eric,Coste, Jacques,Poncet, Joel,Jouin, Patrick,Castro, Bertrand
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p. 2815 - 2816
(2007/10/02)
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- Oxybenzotriazole free peptide coupling reagents for N-methylated amino acids
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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
- Coste, Jacques,Frerot, Eric,Jouin, Patrick,Castro, Bertrand
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p. 1967 - 1970
(2007/10/02)
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- BroP: A new reagent for coupling N-methylated amino acids
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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
- Coste,Dufour,Pantaloni,Castro
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p. 669 - 672
(2007/10/02)
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