- Deprotection of heteroaromatic carbamates via a base-catalyzed methanolysis
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A simple and mild method for the deprotection of heteroaromatic carbamates via methanolysis using a catalytic amount of base such as sodium methoxide, DBU, or Verkade's base (proazaphosphatranes) is presented. Carbamate protecting group of an aliphatic amine is not affected under these conditions.
- Shieh, Wen-Chung,Xue, Song,McKenna, Joe,Prasad, Kapa,Repi?, Oljan,Blacklock, Thomas
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p. 5645 - 5648
(2007/10/03)
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- An efficient synthesis of N-methyl amino acids by way of intermediate 5-oxazolidinones
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N-Methyl amino acids occur in many natural products. Experimental strategies are presented for a unified approach to the synthesis of N-methyl derivatives through 5-oxazolidinones of the 20 common L-amino acids. The amino acids with reactive side chains that required protecting groups or devoted syntheses for side chain construction for N-methylation to proceed included serine, threonine, tyrosine, cysteine, methionine, tryptophan, asparagine, histidine, and arginine. The studies have provided improved methods for the preparation of N-methyl serine, threonine, and tyrosine. All 20 of the common L-amino acids are now available in suitable forms for solid or solution-phase peptide synthesis.
- Aurelio, Luigi,Box, John S.,Brownlee, Robert T. C.,Hughes, Andrew B.,Sleebs, Marianne M.
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p. 2652 - 2667
(2007/10/03)
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- A novel synthesis of N-methyl asparagine, arginine, histidine, and tryptophan
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(graph presented) R = CH2(3-indolyl) tryptophan R = CH2CONH2 asparagine R = CH2(2-imidazolyl) histidine R = CH2CH2CH2(guanidyl) arginine N-Methyl amino acid residues in peptides
- Aurelio, Luigi,Brownlee, Robert T. C.,Hughes, Andrew B.
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p. 3767 - 3769
(2007/10/03)
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- Selective cleavage of Cbz-protected amines
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(MatrixPresented) Under conditions of catalytic Ni(0) and in most cases just over 1 equiv of Me2NH·Br3/K2CO3 or Cs2CO3, a Cbz-protected nitrogen, which is part of a heteroaromatic ring, can
- Lipshutz, Bruce H.,Pfeiffer, Steven S.,Reed, Anthony B.
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p. 4145 - 4148
(2007/10/03)
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- Protease-catalysed synthesis of peptides containing histidine and lysine
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The kinetically controlled α-chymotrypsin- and trypsin-catalysed syntheses of peptides starting from simple acyl donor esters containing histidine at the P1-position (nomenclature according to Schechter and Berger) and lysine derivatives as amino components were examined on the basis of their kinetic parameters. Despite higher specificity constants (k(cat)/K(M)) of trypsin-catalysed ester hydrolysis, α-chymotrypsin- catalysed acyl transfer to N(ε)unprotected lysine derivatives gave higher peptide yields as compared to trypsin-catalysed reactions, whereas in acyl transfer to N(ε)-protected lysine derivatives the trypsin-catalysed reaction gave higher yields. α-Chymotrypsin-catalysed acyl transfer reactions in frozen systems demonstrated the yield-enhancing effect of freezing. Using specific ester leaving groups, both the amount of enzyme and the reaction time can be reduced. In frozen systems the ε-amino function of H-Lys-OH acts as an acyl acceptor at pH ≤9.
- Beck-Piotraschke, Karin,Jakubke, Hans-Dieter
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p. 1505 - 1518
(2007/10/03)
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- Amino acids and peptides. Part 45. Development of a new Nπ-protecting group of histidine, Nπ-(1-adamantyloxymethyl)-histidine, and its evaluation for peptide synthesis
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Nπ-(1-Adamantyloxymethyl)histidine, His(Nπ-1-Adom), is prepared and its properties are examined. The 1-Adom group can be easily removed by trifluoroacetic acid and it is stable to 20% piperidinedimethylformamide and 1 mol dm-3 NaOH. His(Nπ-1-Adom) derivatives can suppress racemization during coupling reactions. His(Nπ-1-Adom) can be used in solid-phase peptide synthesis in combination with fluoren-9-ylmethoxycarbonyl as an Nα-protecting group. Thyrotropin-releasing hormone is successfully synthesized by using His(Nπ-1-Adom).
- Okada, Yoshio,Wang, Jidong,Yamamoto, Takeshi,Mu, Yu,Yokoi, Toshio
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p. 2139 - 2143
(2007/10/03)
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- Synthesis and evaluation of deglycobleomycin A2 analogues containing a tertiary N-methyl amide and simple ester replacement for the L-histidine secondary amide: Direct functional characterization of the requirement for secondary amide metal complexation
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The synthesis and comparative examination of 3-5, analogues of deglycobleomycin A2 (2) which address the inferred importance of the L-histidine secondary amide directly, are detailed. The agent 3 lacks only the L-histidine β-hydroxy group of deglycobleomycin A2 and the corresponding agents 4 and 5 incorporate a tertiary N-methyl amide and simple ester in place of the L-histidine secondary amide. The DNA cleavage properties of 3 proved essentially indistinguishable from those of deglycobleomycin A2 (2) confirming that the distinctions between bleomycin A2 (1) and deglycobleomycin (2) are due to the removal of the disaccharide and not the introduction of the L-histidine free β-hydroxy group. The agents 4 and 5 containing a tertiary N-methyl amide and ester in place of the L-histidine secondary amide were found to cleave duplex DNA but to do so in a nonsequence selective fashion with a substantially reduced efficiency and a diminished double to single strand cleavage ratio that are only slightly greater than that of free iron itself. These latter observations establish the functional requirement for the L-histidine secondary amide and are consistent with the proposals that the L-histidine deprotonated secondary amide is required for functional metal chelation and activity.
- Boger, Dale L.,Teramoto, Shuji,Cai, Hui
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p. 179 - 193
(2007/10/03)
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- Functionalized Basket-Shaped Hosts. Synthesis and Complexation Studies with (Alkali) Matal and Ammonium and Diammonium Ions
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Functionalized basket-shaped hosts have been synthesized from the concave building block 1,3:4,6-bis(3,6-dihydroxy-1,2-xylylene)tetrahydro-3a,6a-diphenylimidazoimidazole-2,5(1H,3H)-dione (1).To this end, N-substituted 1,4,10,13-tetraoxa-7-azatridecamethylene bridges were attached to the 3,6- and 3',6'-positions of the xylylene rings of 1.The substituents at the nitrogen atom in the bridge include: 5-hydroxy-3-oxapentyl, benzyl, hydrogen, 5-(N-(benzyloxycarbonyl)-L-histidyl)-3-dioxapentyl, and 5-acetyl-3-oxapentyl.The baskets complex alkali metal and ammonium guests, as well as aliphatic and aromatic diammonium guests, all in a 1:1 ratio.Using the picrate extraction technique, free energies of binding for the new hosts with 19 guests were determined.Extremely strong binding (-ΔG0 values up to 18 kcal mol-1) was observed for the complexes between the hosts and o-phenylenediammonium dipicrate.The origin of this phenomenon is discussed.The host with histidyl substituents easily forms a 1:1 complex with Zn(OTf)2.
- Smeets, Jan W.,Dalen, Lydia van,Kaats-Richter, Veronica E. M.,Nolte, Roeland J. M.
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p. 454 - 461
(2007/10/02)
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- Peptide-bond Formation, Chemoselective Acylation of Amino Acids, and Crosslinking Reaction between Amino Acids Utilizing a Functional Five-membered Heterocycle, 1,3-Thiazolidine-2-thione
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The monitored aminolysis of 3-acyl-1,3-thiazolidine-2-thiones has been extended to the peptide-bond formation, the chemoselective acylation of amino acids having multifunctional groups, and the crosslinking reaction between amino acids.
- Nagao, Yoshimitsu,Miyasaka, Tadayo,Seno, Kaoru,Fujita, Eiichi,Shibata, Daisuke,Doi, Etsushiro
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p. 2439 - 2446
(2007/10/02)
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