Solid-phase synthesis of 7-acylamino-1,4-benzodiazepine-2,5-diones

A method for the synthesis of polymer-bound 7-acylamino-benzodiazepine-2,5-diones is described. The amino group of an alpha-amino acid is linked to polystyrene or TentaGel resin via reductive amination of polymer-bound 4-alkoxy-2,6-dimethoxybenzaldehyde. Acylation with unprotected 5-nitroanthranilic acid is followed by base-catalyzed ring closure. Reduction of the nitro group yields enantiomerically pure 7-aminobenzodiazepin-2,5-dione attached via the N-4 atom to the resin. Acylation of the amino group on the aromatic ring with acid chlorides in N-methylpyrrolidone (no DMF, no base!) followed by cleavage from the resin using TFA/Me(2)S/water (90:5:5) provides the acylated benzodiazepinones in 52-69% (PS resin) and 41-48% (TG resin) yield (based on the theoretical loading) and >70% purity (HPLC, 210 nm). Using Fmoc-protected tyrosine fluoride in NMP gives the amino acid-coupled benzodiazepinones in 24% (PS resin) and 31% (TG resin) yield.     

合成乳酸正丁酯的主要催化剂述评

综述聚氯乙烯—三氯化铁树脂、强酸性阳离子交换树脂、氨基磺酸、甲基磺酸、维生素C、稀土化合物、硅胶固载硫酸钛、硫酸铁铵、硫酸氢钠、磁性固体超强酸、酸改性高岭土、杂多酸(盐)等数种不同催化剂催化合成乳酸正丁酯的实验结果.结果表明,强酸型阳离子交换树脂、硫酸氢钠、磁性固体超强酸、硅胶固载硫酸钛、活性炭固载杂多酸五种催化剂催化合成乳酸正丁酯的酯收率较高,具有实际使用价值.     

稀土氨基酸固体络合物的合成及结构分析进展

本文综述了稀土氨基酸络合物的合成,以及应用红外、核磁、X-射线衍射、热分析等方法进行结构分析研究的进展情况。     

A Photolabile Carboxyl Protecting Group for Solid Phase Peptide Synthesis

A new kind of photolabile protecting group (PLPG) for carboxyl moieties was designed and synthesized as the linker between resin and peptide. This group can be used for the protection of amino acid carboxyl groups. The peptide was synthesized on Nph (2-hydroxy-3-(2-nitrophenyl)-heptanoic acid)-derivatized resins and could be cleaved under UV exposure, thus avoiding the necessity for harsh acid-mediated resin cleavage. The PLPG has been successfully used for solid-phase synthesis of peptides.     

Solid-phase synthesis of fullerene-peptides

The solid-phase synthesis of peptides (SPPS) containing [60]fullerene-functionalized amino acids is reported. A new amino acid, fulleropyrrolidino-glutamic acid (Fgu), is used for the SPPS of a series of analogues of different length based on the natural Leu(5)-Enkephalin and on cationic antimicrobial peptides. These fullero-peptides were prepared on different solid supports to analyze the influence of the resin on the synthesis. Optimized protocols for the coupling and deprotection procedures were determined allowing the synthesis of highly pure peptides in sufficient quantities for evaluation of biological activities. In particular, to avoid side reactions of the fullerene moiety with bases and nucleophiles, the removal of the protecting groups was performed under inert conditions (nitrogen or argon in the dark). We have encountered serious problems with the recovery of the crude compounds, especially when Fgu was inserted in the proximity of the resin core as fullero-peptides tend to remain embedded inside the resin. Eventually, all of the fullero-peptides were easily purified, and the cationic peptides were tested for their antimicrobial activities. They displayed a specific activity against the Gram-positive bacterium S. aureus and also lysed erythrocytes. The availability of a fullero-amino acid easily useable in the SPPS of fullero-peptides may thus open the way to the synthesis of new types of biologically active oligomers.     

Cap and capture-release techniques applied to solid-phase synthesis of oligosaccharides

This paper reports a new strategy for oligosaccharide synthesis by combining solid-phase methods with cap and capture-release separation techniques, using the p-(5-(ethoxycarbonyl)pentyloxy)benzyl group (CPB) as a tag for the capture of desired oligosaccharides. After a complex carbohydrate mixture was obtained by solid-phase synthesis, the desired oligosaccharide containing a free carboxyl group derived from CPB was attached to an amino resin. The loaded resin was readily separated from side products by filtration and finally treated with acid to release the pure oligosaccharide product.     

A spiroisoxazolinoproline-based amino acid scaffold for solid phase and one-bead-one-compound library synthesis

An efficient, multigram synthesis of a spiroisoxazolinoproline-based amino acid, 7, requiring minimal purification, delivering good cis:trans diastereoselectivity (approximately 1:4), and providing good yields is reported. Surface-bound studies of the reduction of an arylnitro group in the presence of an isoxazoline ring with tin(II) dichloride dihydrate were undertaken to confirm the stability of the isoxazoline ring. Full derivitization of this spiroisoxazolinoproline-based amino acid scaffold was performed during the synthesis of a sample library with high yields and high purity that validated the efficiency of the chemistry that was employed in resin-bound library synthesis. A 129,600 member one-bead-one-compound (OBOC) library based on the scaffold 7 was synthesized utilizing a dual amino acid encoding method and bifunctionalization of TentaGel resin.     

Poly(styrene‐co‐glycerol dimethacrylate): Synthesis,characterization, and application as a resin for gel‐phase peptide synthesis

An efficient cross‐linked polymer support for solid‐phase synthesis was prepared by introducing glycerol dimethacrylate cross‐linker to polystyrene network using free radical aqueous suspension polymerization. The support was characterized by various spectroscopic methods. Morphological feature of the resin was analyzed by microscopy. The polymerization reaction was investigated with respect to the effect of amount of cross‐linking agent, which in turn vary the swelling, loading, and the mechanical stability of the resin. The solvent uptake of the polymer was studied in relation to cross‐linking and compared with Merrifield resin. The stability of the resin was tested in different synthetic conditions used for solid‐phase peptide synthesis. Hydroxy group of the support was derivatized to chloro and then amino groups using different reagents and reaction conditions. Efficiency of the support was tested and compared with TentaGel? resin by following different steps involved in the synthesis of the 65–74 fragment of acyl carrier protein. The results showed that the poly(styrene‐co‐glycerol dimethacrylate) (GDMA‐PS) is equally efficient as TentaGel resin in peptide synthesis. The purity of the peptides was analyzed by HPLC and identities were determined by mass spectroscopy and amino acid analysis. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4382–4392, 2005     

A novel [60]fullerene amino acid for use in solid-phase peptide synthesis

[see structure]. A fullerene derivative containing a free amino group has been condensed with N-Fmoc-L-glutamic acid alpha-tert-butyl ester to give a C60-functionalized amino acid. The carboxylic end of this amino acid has been deprotected in acidic conditions, and the resulting acid has been used for solid-phase peptide synthesis. The final peptide, cleaved from the resin, was very soluble in water solutions and showed antimicrobial activity against two representative bacteria.     

Ferrocene substitution in amino acids strengthens the axial binding in Cu(II) complexes and separates the hydrophobic and hydrophilic region in the crystals

This paper reports on the synthesis, characterization and electrochemical properties of four ferrocenylmethyl substituted L-amino acid ligands and their Cu(II) complexes. Structural characterization of the complexes of L-methionine and L-asparagine derived ligands showed axial coordination of weak thioether and amide respectively to Cu(II). Coordination of the thioether group of L-methionine to copper (2.791 A) is shorter than observed in the electron transfer protein plastocyanin (2.9 A). Methionine thioether does not bind in synthetic Cu(II) complexes. The characterization of bis-complexes (metal : ligand ratio 1 : 2) with L-serine and L-threonine derivatives showed axial coordination of water with a shorter Cu-O bond length compared to that observed in the corresponding amino acid complexes. The structures also revealed separation of the hydrophilic and hydrophobic regions due to amino acid and ferrocene respectively which resulted in the formation of interesting H-bonded networks.     

Application of HR‐MAS NMR in the solid‐phase synthesis of a glycopeptide using Sieber amide resin

The solid‐phase synthesis (SPS) of a structurally complex glycopeptide, using Sieber amide resin, was monitored by high resolution magic angle spinning NMR, demonstrating the further application of this technique. A synthetic peptidoglycan derivative, a precursor of a biologically active PGN, known to be involved in the cellular recognition, was prepared by SPS. The synthesis involved the preparation of an N‐alloc glucosamine moiety and the synthesis of a simple amino acid sequence L ‐Ala‐D ‐Glu‐L ‐Lys‐D ‐Ala‐D ‐Ala. Last step consisted the coupling, on solid‐phase, of the protected muramyl unit to the peptide chain. Proton spectra with good suppression of the polystyrene signals in swollen resin samples were obtained in DMF‐d₇ as a solvent and by using a nonselective 1D TOCSY/DIPSI‐2 scheme, thus allowing to follow the SPS without losses of compound and cleavage from the resin. The assignment of the proton spectra of the resin‐bound amino acid sequence and of the bound glycopeptide was achieved through the combination of MAS COSY, TOCSY and NOESY. Copyright © 2010 John Wiley & Sons, Ltd.     

Tetrafluoroboric acid, a useful deprotecting reagent in peptide synthesis

We have found that tetrafluoroboric acid (HBF4) in trifluoroacetic acid (TFA) in the presence of thioanisole cleaves various protecting groups currently used in peptide synthesis. HBF4 in TFA cleaves an amino acid amide from 4-methylbenzhydrylamine resin more effectively than trifluoromethanesulfonic acid in TFA. Lamprey gonadotropin-releasing hormone (a 10-residue peptide amide) was synthesized using 1 M HBF4-thioanisole in TFA by both solution-phase and solid-phase methods.     

胡蜂蜂毒肽的固相合成

采用Fmoc固相合成策略,合成了胡蜂蜂毒肽(COOH-Ile-Asn-Leu-Lys-Ala-Leu-Ala-Ala-Leu-Ala-Lys-Lys-Ile-Leu-NH₂)。以Wang树脂为载体,HBTU-HOBt为缩合剂,按照其氨基酸序列依次缩合,最终用切割试剂将其从树脂上切割下来,得到粗肽,经RP-HPLC纯化得到目标肽,纯度97.6%。经HR-MS（EI）分析,确定产物为胡蜂蜂毒肽。     

Iron porphyrins catalyze the synthesis of non-protected amino acid esters from ammonia and diazoacetates

Iron complexes of porphyrins (and corroles to a lesser extent) are the first catalysts to utilize ammonia for the synthesis of N-free amino acid esters.     

Catalytic α-allylation of unprotected amino acid esters

Catalytic α-allylation of unprotected amino acid esters to produce α-quaternary α-allyl amino acid esters is reported. Catalytic loadings of picolinaldehyde and Ni(II) salts induce preferential reactivity at the enolizable α-carbon of amino acid esters over the free nitrogen with electrophilic palladium π-allyl complexes. Fourteen examples are given. Additionally, the use of chiral ligands to access enantioenriched α-quaternary amino acid esters from racemic precursors is demonstrated by the enantioselective synthesis of α-allyl phenylalanine methyl ester from racemic phenylalanine methyl ester.     

Trinuclear Organometallic Pt−Ir−Pt Complexes: Insights into Photophysical Properties,Amino Acid Binding and Protein Sensing

The rational synthesis of trinuclear emissive organometallic complexes with two equivalent platinum(II) centres appended to the ancillary substituted 2,2′-bipyridyl ligand of the cyclometalated iridium(III) centre is reported here. The alkynyl-platinum moiety and cyclometalated iridium(III) centres have been separated through a non-conjugated CH₂−O−CH₂ linkage. The emission titration with amino acids reveals that the complexes sense free amino acids. The luminescence sensing of BSA is thus attributed to the amino acid sensing ability of the complexes and confirmed by emission anisotropy and Far-UV CD spectral study. The decrease in α-helix in the CD spectra signifies the changes in the secondary structure of protein in presence of the complexes.     

二茂钛氨基酸配合物的合成新方法

二茂钛衍生物在催化烯烃聚合、氢化、异构化等领域具有重要应用价值[1] ,同时 ,因该类衍生物还具有良好的抗癌性能 ,且其毒性远远低于顺铂类化合物[2 ] ,使人们对这类配合物的研究一直非常重视 .有文献报道 [3] ,以具有生物活性的配体取代二氯二茂钛中的氯原子 ,可以改善其生物利用率 ,提高二茂钛的抗癌活性 .二茂钛配合物的合成绝大多数都是在无水无氧的有机相中进行的 ,在两相(水相 /有机相 ) [4 ,5] 中则很少 .我们曾经在有机相和水相中合成了一些新的二茂钛氨基酸配合物 [6] ,但操作繁杂 ,反应速度慢 ,影响因素多 ,产率低等是这两种体系…     

Copper, nickel, and zinc cyclam-amino acid and cyclam-peptide complexes may be synthesized with "click" chemistry and are noncytotoxic

We describe the synthesis of cyclam metal complexes derivatized with amino acids or a tripeptide using a copper(I)-catalyzed Huisgen "click" reaction. The linker triazole formed during the synthesis plays an active coordinating role in the complexes. The reaction conditions do not racemize the amino acid stereocenters. However, a methylene group adjacent to the triazole is susceptible to H/D exchange under ambient conditions, an observation which has potentially important implications for structures involving stereocenters adjacent to triazoles in click-derived structures. The successful incorporation of several amino acids is described, including reactive tryptophan and cysteine side chains. All complexes are formed rapidly upon introduction of the relevant metal salt, including synthetically convenient cases where trifluoroacetate salts of cyclam derivatives are used directly in the metalation. None of the metal complexes displayed any cytotoxicity to mammalian cells, suggesting that the attachment of such complexes to amino acids and peptides does not induce toxicity, further supporting their potential suitability for labeling/imaging studies. One Cu(II)-cyclam-triazole-cysteine disulfide complex displayed moderate activity against MCF-10A breast nontumorigenic epithelial cells.     

Immobilized Ruthenium Catalyst for Carbon Dioxide Hydrogenation

Carbon dioxide is an ideal source of carbon for incorporation into organic molecules and hydrogenation to formic acid is an attractive choice for CO2 fixation1. When a solvent coexists with supercritical carbon dioxide in a reaction system, the solvent wo…