HOOBt

HOOBt

Efficient preparation of Fmoc-aminoacyl-N-ethylcysteine unit, a key device for the synthesis of peptide thioesters.[Pubmed:21842100]

Org Biomol Chem. 2011 Oct 7;9(19):6807-13.

The synthesis of Fmoc-aminoacyl-N-ethyl-S-triphenylmethylcysteine, an N- to S-acyl migratory device for the preparation of peptide thioesters by Fmoc-SPPS (solid-phase peptide synthesis) is described. Condensation of Fmoc-aminoacyl pentafluorophenyl ester and N-ethyl-S-triphenylmethylcysteine was efficiently performed in the presence of HOOBt (3-hydroxy-3,4-dihydro-4-oxo-1,2,3-benzotriazine) in DMF. A small amount of diastereomer yielded during the reaction was easily separated by HPLC purification and the highly pure devices were obtained for most of the proteinogenic amino acids.

Synthesis of biantennary complex-type nonasaccharyl asn building blocks for solid-phase glycopeptide synthesis.[Pubmed:21612260]

J Org Chem. 2011 Jul 1;76(13):5229-39.

The biantennary complex-type N-glycans bearing LacNAc and LacdiNAc as the nonreducing end motif were synthesized in a protected form suitable to use in the Fmoc solid-phase peptide synthesis studies. Two approaches for the nonasaccharide synthesis were examined by taking advantage of the highly beta-selective glycosylation with GlcNTCA (N-phenyl)trifluoroacetimidate. An earlier approach, which involved the reaction of the trisaccharide donor (Gal-GlcNTCA-Man) and trisaccharide acceptor (Man-GlcNPhth(2)-N(3)), produced a mixture of nonasaccharide isomers. On the other hand, mannosylation of the trisaccharide acceptor (Man-GlcNPhth(2)-N(3)) stereoselectively afforded the known pentasaccharide (Man(3)-GlcNPhth(2)-N(3)), which was reacted with the disaccharyl glycosyl donor (Gal-GlcNTCA or GalNTCA-GlcNTCA) to produce the desired nonasaccharide as a single stereoisomer. Selective dephthaloylation followed by N-acetylation furnished the GlcNAc(2) functionality. The resulting nonasaccharyl azides were condensed with Fmoc-Asp(OPfp)-OBu(t) or Fmoc-Asp(OPfp)-OPac in the presence of Ph(CH(3))(2)P and HOOBt. Finally, the Zn reduction and cleavage of the tert-butyl ester or Zn reduction alone produced the targeted nonasaccharyl Asn building blocks.

Synthesis of a membrane protein with two transmembrane regions.[Pubmed:11991206]

J Pept Sci. 2002 Apr;8(4):172-80.

A membrane protein with two transmembrane domains was synthesized by means of the thioester method. The F1F0 ATP synthase subunit c (Sub.c), which consists of 79 amino acid residues (MW 8257), was chosen as a target. For synthetic purposes, two building blocks, Boc-[Lys34(Boc)]-Sub.c(1-38)-SCH2CH2CO-Ala and Sub.c(39-79), were synthesized via solid-phase methods using Boc chemistry. RP-HPLC purification conditions for the transmembrane peptide were examined. As a result, a combination of a mixture of formic acid, 1-propanol and water with a phenyl column was found to be useful for separating the transmembrane peptide. The purified building blocks were condensed in DMSO in the presence of silver chloride, 3,4-dihydro-3-hydroxy-4-oxo-1,2,3-benzotriazine (HOOBt), N,N-diisopropylethylamine to give the product, Sub.c, after removal of Boc groups (yield 16%). The yield of the condensation reaction could be improved to 23% by raising the reaction temperature to 50 degrees C, and to 26% when a mixture of chloroform and methanol was used as a solvent.

Aza-cycloisodityrosine analogue of RA-VII, an antitumor bicyclic hexapeptide.[Pubmed:24268554]

Bioorg Med Chem Lett. 2013 Dec 15;23(24):6728-31.

An aza-cycloisodityrosine analogue of RA-VII, 3, was designed and synthesized. The key aza-cycloisodityrosine unit was prepared by copper(II)-acetate-mediated intramolecular phenylamine/arylboronic acid coupling of dipeptide followed by connection with the tetrapeptide segment to afford a hexapeptide. Subsequent macrocyclization of the hexapeptide with EDC . HCl and HOOBt under dilute conditions gave 3. Analogue 3 showed significant cytotoxic activity against human promyelocytic leukemia HL-60 cells and human colon carcinoma HCT-116 cells, but its activity was weaker than that of parent peptide RA-VII (1).

Determination of gibberellins in soybean using tertiary amine labeling and capillary electrophoresis coupled with electrochemiluminescence detection.[Pubmed:24184838]

J Chromatogr B Analyt Technol Biomed Life Sci. 2013 Dec 15;941:62-8.

A novel sensitive method based on tertiary amine labeling for the analysis of gibberellins (GAs) by capillary electrophoresis (CE) coupled with electrochemiluminescence (ECL) detection was proposed. GA3 was tagged with 2-(2-aminoethyl)-1-methylpyrrolidine (AEMP) using N, N'-dicyclohexylcarbodiimide (DCC) and 3,4-dihydro-3-hydroxy-4-oxo-1,2,3-benzotriazine (HOOBt) as coupling agents in acetonitrile to produce GA3-AEMP-derivative. The GA3-AEMP-derivative was injected into CE by electrokinetic injection and detected by Ru(bpy)3(2+)-based ECL. The parameters affecting derivatization, detection and separation such as concentration of reactants, detection potential, pH and concentration of separation buffer, were investigated in detail. Under optimum conditions, the linear concentration range for GA3 was from 2.0x10(-7) to 1.28x10(-4)M with a correlation coefficient of 0.9997. The detection limit was 8x10(-8)M (S/N=3). The relative standard deviations of migration time, peak intensity and peak area for nine continuous injections of 2.0x10(-5)M GA3-AEMP-derivative were 1.0%, 2.1% and 4.2%, respectively. The developed approach was successfully applied to the determination of total GAs in the stem, leaf and seed of soybean (Glycine max [L.] Merr.) with recoveries in the range from 89.6% to 99.3%.