1142-20-7Relevant articles and documents
The peculiar behavior of Picha in the formation of metallacrown complexes with Cu(ii), Ni(ii) and Zn(ii) in aqueous solution
Marchi, Luciano,Marchetti, Nicola,Atzeri, Corrado,Borghesani, Valentina,Remelli, Maurizio,Tegoni, Matteo
, p. 3237 - 3250 (2015)
The thermodynamic stability of the metallacrown complexes formed by picolinehydroxamic acid (Picha) with Cu(ii), Ni(ii) and Zn(ii) in aqueous solution has been determined by potentiometry, and the speciation models were validated by ESI-MS and UV-visible spectrophotometry. Cu(ii) and Zn(ii) form 12-MC-4 species as the unique metallacrowns present in the solution. While for Cu(ii) the 12-MC-4 is slightly less stable than that obtained with alaninehydroxamic acid (Alaha), the opposite was found for Zn(ii). Moreover, with Cu(ii) unprecedented 15-MC-5 and 18-MC-6 species were identified under ESI-MS conditions. Picha with Ni(ii) forms, in contrast, a 15-MC-5 complex as a unique metallacrown species. Structural studies of the framework of the 12-MC-4 complexes by ab initio methods were also carried out. The results of our investigations allowed us to rationalize not only the different behaviour of Picha in the formation of metallacrowns with the three metal ions, but also the reasons which underpin the strategies for stabilization of these species reported in the literature using ancillary ligands such as pyridine. This journal is
Epoc group: Transformable protecting group with gold(iii)-catalyzed fluorene formation
Yamamoto, Tomoya,Chang, Tsung-Che,Tanaka, Katsunori
, p. 10703 - 10709 (2021)
This study presents the novel concept of a transformable protecting group, which changes its properties through structural transformation. Based on this concept, we developed a 2-(2-ethynylphenyl)-2-(5-methylfuran-2-yl)-ethoxycarbonyl (Epoc) group. The Epoc group was transformed into an Fmoc-like structure with gold(iii)-catalyzed fluorene formation and was removable under Fmoc-like mild basic conditions post-transformation even though it was originally stable under strongly basic conditions. As an application for organic synthesis, the Epoc group provides the novel orthogonality of gold(iii)-labile protecting groups in solid-phase peptide synthesis. In addition, the high turnover number of fluorene formation in aqueous media is suggestive of the applicability of the Epoc group to biological systems. This journal is
Interactions between Terminally Substituted Amino Acids in an Aqueous and a Non-Aqueous Environment. Enthalpic Interaction Coefficients in Water and in N,N-Dimethylformamide at 25 deg C
Kent, Hilary E.,Lilley, Terence H.,Milburn, Peter J.,Bloemendal, Michael,Somsen, Gus
, p. 101 - 116 (1985)
Enthalpies of dilution of the N-acetyl amides of glycine, L-alanine, L-valine, L-leucine, and L-phenylalanine, dissolved in N,N-dimethylformamide (DMF) as a solvent have been measured at 25 deg C.The results obtained have been analyzed to give the enthalpic interaction (or virial) coefficients of the solutes and these are compared with information previously obtained in aqueous systems.There are marked differences in the interaction properties in the two solvents and, while the additivity approache of Savage and Wood is applicable to the solutes in water it is suitable for representing the interactions in DMF.A correlation is presented between the enthalpic second virial coefficients in DMF and the propensity of side-chains to be in proximity in globular proteins.
Improvement in the one-carbon chain extension of esters with dimethylsulfoxonium methylide
Luong, Hoa,Luss-Lusis, Eduard,Tanoury, Gerald J.,Nugent, William A.
, p. 4238 - 4241 (2013)
A recent report suggests that the reaction of dimethylsulfoxonium methylide with esters does not produce a chain-extended sulfur ylide as previously reported, but rather affords the corresponding carboxylate salt. We have investigated this assertion by using a combination of ab initio molecular orbital calculations, spiking studies, and isotopic labeling. The formation of carboxylate is unambiguously demonstrated to arise through hydrolysis involving adventitious water, principally derived from moisture in commercial trimethylsulfoxonium chloride. Careful vacuum drying of this reagent diminishes the competing hydrolytic pathway resulting in higher yields for the chain-extension reaction than previously reported. Copyright
Cyclodextrin-mediated deacylation of amino acid esters with marked stereoselectivity.
Goto, Koichi,Nakashima, Kentaro,Tanoue, Osamu,Nukushina, Satoshi,Toudo, Isao,Imamura, Chikara,Ihara, Yasuji,Matsumoto, Yoko,Ueoka, Ryuichi
, p. 1283 - 1285 (2002)
With respect to the hydrolysis (deacylation) of Z-D(L)-amino acid esters (N-(benzyloxycarbonyl)-D(L)-amino acid p-nitrophenyl esters) mediated by alpha-, beta- and gamma-cyclodextrins (CyDs), a remarkably high enantioselectivity (L/D=9.0) was observed for the deacylation of Ala substrate with gamma-CyD. The kinetic results on the basis of the Michaelis-Menten principle indicate that the enantioselectivity should be mainly originated in the deacylation process of substrates following the formation of gamma-CyD-substrate (1 : 1) complexes. The computer modeling (molecular mechanics) studies on the inclusion complexes are also described.
The role of protecting groups in the formation of organogels through a nano-fibrillar network formed by self-assembling terminally protected tripeptides
Das, Apurba K.,Bose, Partha Pratim,Drew, Michael G.B.,Banerjee, Arindam
, p. 7432 - 7442 (2007)
A series of eight synthetic self-assembling terminally blocked tripeptides have been studied for gelation. Some of them form gels in various aromatic solvents including benzene, toluene, xylene, and chlorobenzene. It has been found that the protecting groups play an important role in the formation of organogels. It has been observed that, if the C-terminal has been changed from methyl ester to ethyl ester the gelation property does not change significantly (keeping the N-terminal protecting group same), while the change of the protecting group from ethyl ester to isopropyl ester completely abolishes the gelation property. Similarly, keeping the identical C-terminal protecting group (methyl ester) the results of the gelation study indicate that the substitution of N-terminal protection Boc- (tert-butyloxycarbonyl) to Cbz- (benzyloxycarbonyl) does change the gelation property insignificantly, while the change from Boc- to pivaloyl (Piv-) or acetyl (Ac-) group completely eliminates the gelation property. Morphological studies of the dried gels of two of the peptides indicate the presence of an entangled nano-fibrillar network that might be responsible for gelation. FTIR studies of the gels demonstrate that an intermolecular hydrogen bonding network is formed during gelation. Results of X-ray powder diffraction studies for these gelator peptides in different states (dried gels, gel, and bulk solids) reflected that the structure in the wet gel is distinctly different from the dried gel and solid state structures. Single crystal X-ray diffraction studies of a non-gelator peptide, which is structurally similar to the gelator molecules reveal that the peptide forms an antiparallel β-sheet structure in crystals.
STEREOSELECTIVE HYDROLYSIS OF AMINO ACID ESTERS BY MODIFIED POLY(ETHYLENIMINE)S WITH COVALENTLY-LINKED DIPEPTIDE CONTAINING A HISTIDYL RESIDUE
Kimura, Yoshiharu,Nango, Mamoru,Ihara, Yasuji,Kuroki, Nobuhiko
, p. 429 - 432 (1984)
Stereoselective hydrolyses of chiral substrates were examined in poly(ethylenimine) derivatives with optically active groups.A high stereoselective effect, kL/kD = 3.6, is observed.The effect of the substrate structure influenced both the rate constant and the stereoselective ratio in the hydrolyses by poly(ethylenimine) derivatives.
STEREOSELECTIVE HYDROLYSIS OF AMINO ACID ESTERS IN MODIFIED LINEAR POLY(ETHYLENIMINE) DOMAINS
Kimura, Yoshiharu,Kanda, Shinichi,Nango, Mamoru,Ihara, Yasuji,Koga, Joichi,et al.
, p. 433 - 436 (1984)
A large rate enhancement and a stereoselective preference are exhibited in the hydrolysis catalysed by N-decanoyl-L-histidine (2a) and a dipeptide containing L-histidyl residue (2b) in the domain of linear poly(ethylimine) derivatives.
Enantioconvergent Cu-Catalyzed Radical C-N Coupling of Racemic Secondary Alkyl Halides to Access α-Chiral Primary Amines
Cheng, Jiang-Tao,Dong, Xiao-Yang,Gu, Qiang-Shuai,Li, Zhong-Liang,Liu, Juan,Liu, Xin-Yuan,Luan, Cheng,Wang, Fu-Li,Wang, Li-Lei,Yang, Ning-Yuan,Zhang, Yu-Feng
supporting information, p. 15413 - 15419 (2021/09/30)
α-Chiral alkyl primary amines are virtually universal synthetic precursors for all other α-chiral N-containing compounds ubiquitous in biological, pharmaceutical, and material sciences. The enantioselective amination of common alkyl halides with ammonia is appealing for potential rapid access to α-chiral primary amines, but has hitherto remained rare due to the multifaceted difficulties in using ammonia and the underdeveloped C(sp3)-N coupling. Here we demonstrate sulfoximines as excellent ammonia surrogates for enantioconvergent radical C-N coupling with diverse racemic secondary alkyl halides (>60 examples) by copper catalysis under mild thermal conditions. The reaction efficiently provides highly enantioenrichedN-alkyl sulfoximines (up to 99% yield and >99% ee) featuring secondary benzyl, propargyl, α-carbonyl alkyl, and α-cyano alkyl stereocenters. In addition, we have converted the masked α-chiral primary amines thus obtained to various synthetic building blocks, ligands, and drugs possessing α-chiral N-functionalities, such as carbamate, carboxylamide, secondary and tertiary amine, and oxazoline, with commonly seen α-substitution patterns. These results shine light on the potential of enantioconvergent radical cross-coupling as a general chiral carbon-heteroatom formation strategy.
A General Stereocontrolled Synthesis of Opines through Asymmetric Pd-Catalyzed N-Allylation of Amino Acid Esters
Albat, Dominik,Neud?rfl, J?rg-Martin,Schmalz, Hans-Günther
supporting information, p. 2099 - 2102 (2021/07/22)
A stereo-divergent synthesis of natural and unnatural opines in stereochemically pure form is based on the direct palladium-catalyzed N-allylation of α-amino acid esters (up to 97 % ee or 99 : 1 d.r.) using methyl (E)-2-penten-4-yl carbonate in the presence of only 1 mol% of a catalyst, prepared in-situ from the C2-symmetric diphosphine iPr-MediPhos and [Pd(allyl)Cl]2. Selected target compounds (incl. a derivative of the drug enalapril) were efficiently obtained from the N-allylated intermediates by oxidative cleavage (ozonolysis) of the allylic C=C bond under temporary N-Boc-protection.
