- Synthesis of Fmoc-Protected Amino Alcohols via the Sharpless Asymmetric Aminohydroxylation Reaction Using FmocNHCl as the Nitrogen Source
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The aminohydroxylation of various alkenes using FmocNHCl as a nitrogen source is reported. In general, in the absence of a ligand, the reaction provided racemic Fmoc-protected amino alcohols with excellent regioselectivity but in low to moderate yields. However, in some instances, the yield of an amino alcohol product and the regioselectivity could be altered by the addition of a catalytic amount of triethylamine (TEA). The Sharpless asymmetric variant of this reaction (Sharpless asymmetric aminohydroxylation (SAAH)), using (DHQD)2PHAL (DHQD) or (DHQ)2PHAL (DHQ) as chiral ligands, proceeded more readily and in higher yield compared to the same reaction in the absence of a chiral ligand. The enantiomeric ratios (er) of all but two examples exceeded 90:10 with many examples giving er values of 95:5 or higher, making FmocNHCl a highly practical reagent for preparing chiral amino alcohols. The SAAH reaction using FmocNHCl was used for the preparation of d-threo-β-hydroxyasparagine and d-threo-β-methoxyaspartate, suitably protected for Fmoc solid phase peptide synthesis.
- Moreira, Ryan,Diamandas, Matthew,Taylor, Scott D.
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p. 15476 - 15485
(2019/11/21)
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- Alzheimer's disease: Identification and development of β-secretase (BACE-1) binding fragments and inhibitors by dynamic ligation screening (DLS)
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The application of dynamic ligation screening (DLS), a methodology for fragment-based drug discovery (FBDD), to the aspartic protease β-secretase (BACE-1) is reported. For this purpose, three new fluorescence resonance energy transfer (FRET) substrates we
- Fernandez-Bachiller, Maria Isabel,Horatscheck, Andre,Lisurek, Michael,Rademann, Joerg
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p. 1041 - 1056
(2013/07/26)
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- N-urethane-protected amino alkyl isothiocyanates: Synthesis, isolation, characterization, and application to the synthesis of thioureidopeptides
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(Chemical Equation Presented) Synthetically useful N-Fmoc amino-alkyl isothiocyanates have been described, starting from protected amino acids. These compounds have been synthesized in excellent yields by thiocarbonylation of the monoprotected 1,2-diamines with CS2/TEA/p-TsCl, isolated as stable solids, and completely characterized. The procedure has been extended to the synthesis of amino alkyl isothiocyanates from Boc- and Z-protected amino acids as well. The utility of these isothiocyanates for peptidomimetics synthesis has been demonstrated by employing them in the preparation of a series of dithioureidopeptide esters. Boc-Gly-OH and Boc-Phe-OH derived isothiocyanates 9a and 9c have been obtained as single crystals and their structures solved through X-ray diffraction. They belong to the orthorhombic crystal system, and have a single molecule in the asymmetric unit (Z′ = 1). 9a crystallizes in the centrosymmetric space group Pbca, while 9c crystallizes in the noncentrosymmetric space group P212121.
- Sureshbabu, Vommina V.,Naik, Shankar A.,Hemantha,Narendra,Das, Ushati,Guru Row, Tayur N.
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supporting information; experimental part
p. 5260 - 5266
(2009/12/06)
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- Efficient synthesis of N-fmoc-aminoalkoxy pentafluorophenyl carbonates: Application for the synthesis of oligopeptidyl carbamates
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N-Fmoc-Aminoalkoxy pentafluorophenyl carbonates have been synthesized through the reaction of N-Fmoc-aminoalkoxy carbonyl chloride with pentafluorophenol. The reaction was clean and high yielding, and the products have been fully characterized using infra
- Sureshbabu, Vommina V.,Hemantha
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body text
p. 3555 - 3566
(2009/12/26)
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- Truly catalytic and chemoselective cleavage of benzylidene acetal with phosphomolybdic acid supported on silica gel
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Phosphomolybdic acid supported on silica gel provides a truly catalytic method for the chemoselective cleavage of benzylidene acetals having sensitive functional groups under mild conditions. It is easy to perform on large scale owing to minimal catalyst loading (0.5 mol-%). Several sensitive functional groups such as TBDPS ether, -OMs, -OAc, allyl ether, N-Boc, N-Fmoc and N-Cbz are stable under the reaction conditions. In addition, benzylidene acetal is selectively cleaved in the presence of isopropylidene ketal. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Kumar, Ponminor Senthil,Kumar, Gaddale Devanna Kishore,Baskaran, Sundarababu
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supporting information; scheme or table
p. 6063 - 6067
(2009/05/27)
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- Efficient loading of primary alcohols onto a solid phase using a trityl bromide linker
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The Letter describes an improved, rapid and mild strategy for the loading of primary alcohols onto a polystyrene trityl resin via a highly reactive trityl bromide linker. This protocol facilitates an efficient resin loading even of acid-sensitive or heat-
- Crestey, Fran?ois,Ottesen, Lars K.,Jaroszewski, Jerzy W.,Franzyk, Henrik
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body text
p. 5890 - 5893
(2009/04/05)
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- Synthesis of Fmoc-protected β-amino alcohols and peptidyl alcohols from Fmoc-amino acid/peptide acid azides
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An efficient synthesis of Nα-9H-fluoren-9- ylmethoxycarbony(Fmoc)-β-amino alcohols by the reduction of Fmoc-α-amino acyl azides employing aqueous NaBH4 as a reducing agent has been described. The reduction is found to be simple and almost complete. All the Fmoc-β-amino alcohols prepared are fully characterized by 1H and 13C NMR and mass spectrometry. Further, the method is extended for the reduction of seven Fmoc-dipeptidyl acids to the corresponding alcohols. Their reduction is also found to be smooth and complete.
- Babu, Vommina V. Suresh,Kantharaju,Sudarshan, Naremaddepalli S.
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p. 1880 - 1886
(2007/10/03)
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- Asymmetric synthesis of highly substituted azapolycyclic compounds via 2-alkenyl sulfoximines: Potential scaffolds for peptide mimetics
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The application of metalated, enantiomerically pure acyclic and cyclic 2-alkenyl sulfoximines for the synthesis of highly substituted aza(poly)cyclic ring systems is described. The method relies on a one-pot combination of a reagent-controlled allyl transfer reaction to α- or β-amino aldehydes, followed by a Michael-type cyclization of the intermediate vinyl sulfoximines generated in the first step. The sulfur-free target compounds are preferentially obtained by samarium iodide treatment of the sulfonimidoyl substituted heterocycles. In addition to this methodological work, initial results on the biological activity of selected examples are reported. Furthermore, a concept for the transformation of peptidic lead structures into non-peptide mimetics is described, and the relevance of the new approach to highly substituted azaheterocycles in this context is discussed.
- Reggelin, Michael,Junker, Bernd,Heinrich, Timo,Slavik, Stefan,Buehle, Philipp
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p. 4023 - 4034
(2007/10/03)
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- A facile, catalytic, and environmentally benign method for selective deprotection of teri-butyldimethylsilyl ether mediated by phosphomolybdic acid supported on silica gel
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An environmentally benign PMA supported on SiO2 is found to be an efficient catalyst for the chemoselective deprotection of TBDMS ethers under very mild conditions. Various labile functional groups such as isopropylidene acetal, OTBDPS, OTHP, Oallyl, OBn, alkene, alkyne, OAc, OBz, N-Boc, N-Cbz, N-Fmoc, mesylate, and azide are found to be stable under the reaction conditions. This "truly catalytic" heterogeneous reaction does not require aqueous workup, and the supported catalyst and the solvent can be readily recovered and recycled.
- Kishore Kumar,Baskaran, Sundarababu
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p. 4520 - 4523
(2007/10/03)
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- A mild, efficient, and inexpensive protocol for the selective deprotection of TBDMS ethers using KHSO4
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Potassium hydrogensulfate in 30% aq. methanol deprotects a variety of tert-butyldimethylsilyl ethers at room temperature in excellent yields.
- Arumugam, Pandurangan,Karthikeyan, Ganesan,Perumal, Paramasivan T.
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p. 1146 - 1147
(2007/10/03)
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