201353-89-1Relevant articles and documents
General Fmoc-Based Solid-Phase Synthesis of Complex Depsipeptides Circumventing Problematic Fmoc Removal
Lobo-Ruiz, Ariadna,Tulla-Puche, Judit
supporting information, p. 183 - 192 (2020/01/24)
Development of an Fmoc-based solid-phase depsipeptide methodology has been hampered by base-promoted fragmentation and diketoperazine formation upon Fmoc group elimination. Such a strategy would be a useful tool given the number of commercially available Fmoc-protected residues. Herein we report that the addition of small percentages of organic acids to the Fmoc-removal cocktail proves effective to circumvent these drawbacks and most importantly, allowed the development of an exclusively solid-phase stepwise methodology to prepare a highly complex depsipeptide with multiple and consecutive esters bonds. Alongside, the optimal protecting group scheme for residue incorporation, which is not as straightforward as it is for traditional peptide synthesis, was explored. The developed stepwise strategy proved effective for the synthesis of a highly complex cyclodepsipeptide, being comparable to the yields obtained when using traditional combined chemistry approaches.
Polypeptide raw material N-fluorenylmethoxycarbonyl-O-tert-butyl threonine preparation method
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Paragraph 0012-0014, (2019/01/23)
The invention discloses a polypeptide raw material N-fluorenylmethoxycarbonyl-O-tert-butyl threonine preparation method, and mainly solves the technical problems of complexity, long cycle, more wastegas, waste water and industrial residues, high cost, high dangerousness and the like in an original process. The preparation method includes the steps: first, suspending threonine in methanol, reducing temperature, dropping thionyl chloride and then removing solvents by concentration after temperature reaction to obtain threonine methyl ester hydrochloride; second, dissolving the threonine methylester hydrochloride in methylene dichloride, leading in isobutene, concentrating sulfuric acid and performing sealed reaction treatment to obtain oily O-tert-butyl threonine methyl ester; third, dissolving the O-tert-butyl threonine methyl ester in water and acetone, adding sodium hydroxide, enabling pH (potential of hydrogen) to be 11-12, performing reaction to obtain O-tert-butyl threonine solution, adding 9-fluorenylmethyl-N-succinimidyl carbonate, maintaining the pH of 8-9 of a system by the aid of alkali liquor, performing washing acidification extraction after reaction and performing treatment to obtain N-fluorenylmethoxycarbonyl-O-tert-butyl threonine serving as a final product.
A mild removal of Fmoc group using sodium azide
Chen, Chun-Chi,Rajagopal, Basker,Liu, Xuan Yu,Chen, Kuan Lin,Tyan, Yu-Chang,Lin, Fui,Lin, Po-Chiao
, p. 367 - 374 (2014/03/21)
A mild method for effectively removing the fluorenylmethoxycarbonyl (Fmoc) group using sodium azide was developed. Without base, sodium azide completely deprotected Nα-Fmoc-amino acids in hours. The solvent-dependent conditions were carefully studied and then optimized by screening different sodium azide amounts and reaction temperatures. A variety of Fmoc-protected amino acids containing residues masked with different protecting groups were efficiently and selectively deprotected by the optimized reaction. Finally, a biologically significant hexapeptide, angiotensin IV, was successfully synthesized by solid phase peptide synthesis using the developed sodium azide method for all Fmoc removals. The base-free condition provides a complement method for Fmoc deprotection in peptide chemistry and modern organic synthesis. Graphical Abstract: [Figure not available: see fulltext.]
DIARYLSULPHID BACKBONE CONTAINING PHOTOLABILE PROTECTING GROUPS
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Page/Page column 42, (2012/10/18)
The present invention relates to photoactivable protecting groups containing a diarylsulphid chromophore, a method for the synthesis thereof and their use as photoactivable protecting groups using maskless photolithography based array synthesis. wherein R2 is [Formula II] or wherein R2 is [Formula III] or [Formula IV] wherein R7 is a natural amino acid, a non-natural amino acid or an amino acid derivative forming an urethan bond to formula Ib, or wherein formula IV represents the carboxy function of a natural amino acid, a non-natural amino acid or an amino acid derivative, forming an ester bond to formula Ib.
Total synthesis of the large non-ribosomal peptide polytheonamide B
Inoue, Masayuki,Shinohara, Naoki,Tanabe, Shintaro,Takahashi, Tomoaki,Okura, Ken,Itoh, Hiroaki,Mizoguchi, Yuki,Iida, Maiko,Lee, Nayoung,Matsuoka, Shigeru
supporting information; scheme or table, p. 280 - 285 (2010/09/03)
Polytheonamide B is by far the largest non-ribosomal peptide known at present, and displays extraordinary cytotoxicity (EC50 =68 pg ml -1 , mouse leukaemia P388 cells). Its 48 amino-acid residues include a variety of non-proteinogenic d- and l-amino acids, and the absolute stereochemistry of these amino acids alternate in sequence. These structural features induce the formation of a stable β-strand-type structure, giving rise to an overall tubular structure over 30A? in length. In a biological setting, this fold is believed to transport cations across the lipid bilayer through a pore, thereby acting as an ion channel. Here, we report the first chemical construction of polytheonamide B. Our synthesis relies on the combination of four key stages: syntheses of non-proteinogenic amino acids, a solid-phase assembly of four fragments of polytheonamide B, silver-mediated connection of the fragments and, finally, global deprotection. The synthetic material now available will allow studies of the relationships between its conformational properties, channel functions and cytotoxicity.
Thermal cleavage of the Fmoc protection group
Hoeck, Stefan,Marti, Roger,Riedl, Rainer,Simeunovic, Marina
experimental part, p. 200 - 202 (2011/08/05)
The Fmoc protection group is among the most commonly used protection groups for the amino function. A fast method for the thermal deavage of this protection group under base-free conditions without the need for dibenzofulvene scavengers is presented. The advantages of this method include straightforward testability by means of a simple high-temperature NMR experiment, usually high yields, and good selectivity towards the BOC protection group and t-butyl ethers.
2,2-Difluoro-1,3,2-oxazaborolidin-5-ones: Novel approach for selective side-chain protection of serine and threonine
Wang, Jidong,Okada, Yoshio,Li, Wei,Yokoi, Toshio,Zhu, Jintao
, p. 621 - 624 (2007/10/03)
2,2-Difluoro-1,3,2-oxazaborolidin-5-ones 1, which are synthesized from BF3 and salts of amino acids, are highly effective, convenient and, moreover, inexpensive intermediates for the simultaneous protection of both α-amino and α-carboxy groups in α-amino acids. The new method streamlines the hitherto tedious procedures for side-chain protection of Ser and Thr. Ser(Bu′), Thr(Bu′), Ser(Bzl) and Thr(Bzl) are obtained by this procedure in high yields and in pure form using highly reactive reagents.
Effect of the Side Chain on the Racemization of Amino Acids in Aqueous Solution
Smith, Grant Gill,Reddy, G. Vanita
, p. 4529 - 4535 (2007/10/02)
The rate of racemization of 13 amino acids possessing hydroxy, carboxy, alkoxy, carboalkoxy, alkyl, aryl, and thioether side chains were compared.Reaction conditions were identical for all amino acids studied.Gas chromatography was used to determine the percent of D isomer present.Hydroxy amino acids racemized most rapidly, but conversion to an ether function reduced the rate considerably.The increased racemization rate of methionine (R = CH2CH2SCH3) over Ala (R = CH3) has been attributed to orbital overlap from the sulfur.Asp racemized faster than Glu, α-aminoadipic acid, and pyroglutamic acid. β- and γ-monomethyl esters of aspartic and glutamic acids, respectively, racemized only slightly faster than the corresponding free acids.The slight increase in rate appears attributable to a solvent change brought on by ester hydrolysis.Under the reaction conditions, pH 8 and 140 deg C, hydrolysis of the esters competed favorably with racemization at the methine carbon.The relatively lower racemization rate observed in the case of Glu compared with Asp resulted from the slow formation of pyroglutamic acid.Pyroglutamic acid racemized at a considerably slower rate than acidic amino acids.The differences in the racemization rates with changes in the R group are discussed in terms of several factors, including intramolecular reactions, direct field effects, orbital overlap, and solvation effects, as well as inductive, resonance, and steric factors.
Process for preparing tert-butyl ether or ester containing polyfunctional organic compounds
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, (2008/06/13)
For the preparation of polyfunctional organic compounds having at least one functional group of medium nucleophilic character selectively blocked by a tertiary butyl group, the corresponding unblocked compound is dissolved in a solution of concentrated sulfuric acid in an organic ether, and excess liquid isobutene is added to the solution at a temperature of not more than 5° C.
Studies on 2-Aziridinecarboxylic Acid. VI. Synthesis of β-Alkoxy-α-Amino Acids via Ring-opening Reaction of Aziridine
Nakajima, Kiichiro,Neya, Masahiro,Yamada, Shinichi,Okawa, Kenji
, p. 3049 - 3050 (2007/10/02)
The reaction of aziridine derivatives having a urethane-type protecting group with several alcohols in the presence of boron trifluoride etherate afford the corresponding optically pure O-alkylserine and O-alkylthreonine derivatives via a ring-opening reaction of aziridine in good yield.
