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1.
Molecular templates bind particular reactants, thereby increasing their effective concentrations and accelerating the corresponding reaction. This concept has been successfully applied to a number of chemical problems with a strong focus on nucleic acid templated reactions. We present the first protein‐templated reaction that allows N‐terminal linkage of two peptides. In the presence of a protein template, ligation reactions were accelerated by more than three orders of magnitude. The templated reaction is highly selective and proved its robustness in a protein‐labeling reaction that was performed in crude cell lysate.  相似文献   

2.
While photochemical synthesis offers access to spatiotemporal reaction control, its potential to selectively address specific reactions by the colour of light is usually limited by ubiquitous spectral absorption overlaps of the reactive groups. Herein, a new concept is introduced that actively suppresses one ligation reaction by triggering the cycloreversion of the [2+2] cycloaddition of styrylpyrene. Combination of the photoreversible styrylpyrene chemistry with the [4+4] cycloaddition of 9‐triazolylanthracene makes it possible to initially induce chain coupling using UV light and to subsequently ligate the formed single‐chain nanoparticle (SCNP) with a second polymer chain using blue light. Seizing upon the first sequence‐independent λ‐orthogonal reactivity established here, the same macromolecular architecture was obtained in reverse irradiation sequence, by blue and subsequent violet light irradiation—completely foregoing high‐energy UV light.  相似文献   

3.
4.
Native chemical ligation enables the chemical synthesis of proteins. Previously, thiol‐containing auxiliary groups have been used to extend the reaction scope beyond N‐terminal cysteine residues. However, the N‐benzyl‐type auxiliaries used so far result in rather low reaction rates. Herein, a new Nα‐auxiliary is presented. Consideration of a radical fragmentation for cleavage led to the design of a new auxiliary group which is selectively removed under mildly basic conditions (pH 8.5) in the presence of TCEP and morpholine. Most importantly and in contrast to previously described auxiliaries, the 2‐mercapto‐2‐phenethyl auxiliary is not limited to Gly‐containing sites and ligations succeed at sterically demanding junctions. The auxiliary is introduced in high yield by on‐resin reductive amination with commercially available amino acid building blocks. The synthetic utility of the method is demonstrated by the synthesis of two antimicrobial proteins, DCD‐1L and opistoporin‐2.  相似文献   

5.
6.
The transamination reaction of M[N(SiMe3)2]2 with (2‐pyridylmethyl)(tert‐butyldimethylsilyl)amine yields the corresponding homoleptic metal bis[(2‐pyridylmethyl)(tert‐butyldimethylsilyl)amides] of Mg ( 1 ), Mn ( 2 ), Fe ( 3 ), Co ( 4 ) and Zn ( 5 ). All these compounds crystallize from hexane isotypic in the space group C2/c. From toluene the zinc derivative precipitates as toluene solvate 5 ·toluene. The molecular structures of these compounds are very similar with large NMN angles to the amide nitrogen atoms with NMN values of 148° ( 1 ) and 150° ( 5 ) for the diamagnetic compounds and 156° for the paramagnetic derivatives 2 and 3 . The Co derivative 4 displays a rather small NCoN angle of 142°. Different synthetic routes have been explored for compound 3 which is also available via the metallation reaction of bis(2,4,6‐trimethylphenyl)iron with (2‐pyridylmethyl)(tert‐butyldimethylsilyl)amine and via the metathesis reaction of lithium (2‐pyridylmethyl)(tert‐butyldimethylsilyl)amide with [(thf)2FeCl2]. In course of the metathesis reaction, an equimolar amount of lithium (2‐pyridylmethyl)(tert‐butyldimethylsilyl)amide and [(thf)2FeCl2] yields heteroleptic (2‐pyridylmethyl)(tert‐butyldimethylsilyl)amido iron(II) chloride ( 6 ) which crystallizes as a centrosymmetric dimeric molecule. The oxidative C‐C coupling reaction of 5 with Sn[N(SiMe3)2]2 leads to the formation of tin(II) 1,2‐bis(2‐pyridyl)‐1,2‐bis(tert‐butyldimethylsilylamido)ethane, tin metal and Zn[N(SiMe3)2]2.  相似文献   

7.
8.
The preparative value of one-pot, multicomponent, sequential Michael-Michael-ring-closure reactions followed by aromatization is illustrated in two ways: (1) by a multi-gram example, and (2) by a total synthesis of juncunol, an unusual vinyldihydrophenanthrene.  相似文献   

9.
The substitution and insertion reactions of H2SiLiF (A) with CH3XHn−1 (X = F, Cl, Br, O, N; n = 1, 1, 1, 2, 3) have been studied using density functional theory. The results indicate that the substitution reactions of A with CH3XHn−1 proceed via two reaction paths, I and II, forming the same product H2SiFCH3. The insertion reactions of A with CH3XHn−1 form H2SiXHn−1CH3. The following conclusions emerge from this work. (i) The substitution reactions of A with CH3XHn−1 occur in a concerted manner. The substitution barriers of A with CH3XHn−1 for both pathways decrease with the increase of the atomic number of the element X for the same family systems or for the same row systems. Path I is more favorable than path II. (ii) A inserts into a C-X bond via a concerted manner, and the reaction barriers increase for the same-row element X from right to left in the periodic table, whereas change very little for the systems of the same-family element X. (iii) The substitution reactions occur more readily than the insertion reactions for A with CH3XHn−1 systems. (iv) All substitution and insertion reactions of A with CH3XHn−1 are exothermic. (v) In solvents, the substitution reaction process of A with CH3XHn−1 is similar to that in vacuum. The barrier heights in solvents increase in the order CH3F < CH3Cl < CH3Br < CH3OH < CH3NH2. The solvent polarity has little effects on the substitution barriers. The calculations are in agreement with experiments.  相似文献   

10.
11.
The light‐induced formation of a covalent bond between an alkene group and a tetrazole moiety has been used for the selective labeling of proteins in vitro and in live cells. This bioorthogonal ligation initiated by brief irradiation with UV light leads to a fluorescent pyrazoline adduct (see scheme).

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12.
Here we report on our studies on combinations of amino acids and copper(I) for catalyzing multicomponent reactions (MCRs). We aimed to prepare both diene and dienophiles simultaneously, under very mild and environmentally friendly conditions, thus giving the constituents for a stereocontrolled Diels-Alder reaction, which in turn yields compounds 4 to 8. A diversity-oriented synthesis of polysubstituted spirotriones 4 to 6 were assembled from simple substrates like 1-(triphenylphosphanylidene)-propan-2-one, two aldehydes, and cyclic-1,3-diketones through Wittig/Knoevenagel/Diels-Alder and aldol/Knoevenagel/Diels-Alder reaction sequences in one pot under stereospecific organocatalysis. Chemical diversity libraries of polysubstituted spirotrione-1,2,3-traizoles 8 were assembled from simple substrates by means of Wittig/Knoevenagel/Diels-Alder/Huisgen cycloaddition reaction sequences in one pot under stereospecific organo/Cu(I) catalysis. Functionalized dispirolactones such as 6 are biologically active antioxidants and radical scavengers, and spirotrione-1,2,3-traizoles 8 have found wide applications in chemistry, biology, and materials science. Experimentally simple and environmentally friendly, organocatalytic, asymmetric four-component Diels-Alder (AFCDA) reactions of 1-(triphenylphosphanylidene)- propan-2-one, two different aldehydes, and cyclic-1,3-diketones produced diastereospecific and highly enantioselective substituted spirotriones 4 by means of a Wittig/Knoevenagel/Diels-Alder reaction sequence in one pot. Additionally we have developed an organocatalytic, asymmetric three-component Michael (ATCM) reaction of 1-(triphenylphosphanylidene)-propan-2-one, aldehyde, and cyclic-1,3-diketones that produced Michael adducts 15, 16 through a Wittig/Michael reaction sequence in a highly enantioselective one-pot process.  相似文献   

13.
Herein, the reaction of (1-methyl-1 H-benzo[d]imidazol-2-yl)methanamine ( L1 ) with Co(H2O)6Cl2, in CH3CN at 120 °C, leading to the 2,3,5,6-tetrakis(1-methyl-1 H-benzo[d]imidazol-2-yl)pyrazine ( 3 ), isolated as a dimeric cluster {[CoII2( 3 )Cl4] ⋅ 2 CH3CN} ( 2 ), is reported. When O2 and H2O are present, (1-methyl-1 H-benzo[d]imidazole-2-carbonyl)amide (H L1′ ) is first formed and crystallized as [CoIII( L1 )2( L1′ )]Cl2 ⋅ 2 H2O ( 4 ) before fusion of H L1′ with L1 , giving 1-methyl-N-(1-methyl-1 H-benzo[d]imidazol-2-carbonyl)-1 H-benzo[d]imidazol-2-carboxamide (H L2′′ ) forming a one-dimensional (1D) chain of [CoII3( L2′′ )2Cl4]n ( 5 ). The combination of crystallography and mass spectrometry (ESI-MS) of isolated crystals and the solutions taken from the reaction as a function time reveal seven intermediate steps leading to 2 , but six steps for 5 , for which a different sequence takes place. Control and isotope labeling experiments confirm the two carbonyl oxygen atoms in 5 originate from both air and water. The dependence on the metals, compared with FeCl3 ⋅ 6 H2O leading to a stable triheteroarylmethyl radical, is quite astounding, which could be attributed to the different oxidation states of the metals and coordination modes confirmed by DFT calculations. This metal and valence dependent process is a very useful way for selectively obtaining these large molecules, which are unachievable by common organic synthesis.  相似文献   

14.
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16.
The synthesis of cyclopenta[c]pyrazoles from γ,δ-unsaturated aldehydes by a domino sequence involving one-carbon homologation and intramolecular azomethine imine 1,3-dipolar cycloaddition is disclosed. The fused pyrazoles bearing aromatic and aliphatic substituents are obtained in good yields and excellent diastereomeric purity. Additionally, the synthetic utility of the pyrazole products generated by this method has been highlighted in a series of functionalization reactions. The method presented opens strategic opportunities for the synthesis of pyrazole-containing biologically active compounds.  相似文献   

17.
18.
α,β-Unsaturated aldehydes were smoothly alkylated by radicals generated through photosensitised hydrogen abstraction of benzophenone. In this way, and by using 1,3-dioxolane as radical precursor, monoprotected 1,4-dialdehydes were obtained from crotonaldehyde, 2-hexenal, 4-methyl-2-pentenal and cyclohexencarboxyaldehyde in a moderate yield, and in a low yield from β-aryl-α,β-unsaturated aldehydes. With 2-alkyl-1,3-dioxolanes, monoprotected 1,4-ketoaldehydes were analogously prepared. By using methanol, ethanol and isopropanol as radical precursors γ-lactols were likewise obtained from the above aliphatic aldehydes. These single-step syntheses compared favorably with multi-step approaches previously proposed for some of these compounds. The lactols were conveniently oxidized to the corresponding γ-lactones. An alternative to the photosensitisation in organic medium was the use of mixed aqueous-organic solvent and a hydrosoluble photosensitiser (benzophenone disodium disulfonate was prepared for this purpose and successfully used), which allowed a more convenient work up.  相似文献   

19.
An efficient and regioselective procedure for the synthesis of a series of alkyl(aryl/heteroaryl) substituted 3-trifluoromethyl-1H-1-phenylpyrazoles and alkyl 3-carboxylate analogs, from the cyclocondensation reactions of 4-alkoxy-1,1,1-trihaloalk-3-en-2-ones [CX3C(O)CR2=CR1(OMe/OEt), where R1 = H, Me, Ph, 2-Furyl; R2 = H; R1-R2 = -C4H8- and X = F, Cl] and 1-phenylsemicarbazide in an acidified alcoholic medium (R3OH/H2SO4), where R3 = Me, Et, Pri was successfully applied and is described here in detail.  相似文献   

20.
Optimal conditions for the preparation of 9-ethyl-, 9,12-diethyl, 8,9,12-triethyl-, and 8,9,10,12-tetraethyl-o-carboranes under the action of EtBr on o-carborane in the presence of AICl3 were determined. The behavior of these o-carborane derivatives towards electrophilic and nucleophilic reagents was studied. The presence of four ethyl groups in positions 8, 9, 10, and 12 of the carborane polyhedron increases the electron density on the boron atoms in positions 4, 5, 7, and II to the point where they are able to enter into reactions of electrophilic substitution, and in positions 3 and 6 to the point that they become resistant to the action of nucleophilic reagents. Reactions of 1,2-dilithium-8,9,10,12-tetraethyl-o-carborane with various electrophilic reagents were studied.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp 2755–2763, November, 1996.  相似文献   

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