- Synthesis and relaxometric characterization of a MRI Gd-based probe responsive to glutamic acid decarboxylase enzymatic activity
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Novel contrast agent based systems, which selectively visualize specific cells, e.g., neurons in the brain, would be of substantial importance for the fast developing field of molecular magnetic resonance imaging (MRI). We report here the synthesis and in vitro validation of a Gd(III)-based contrast agent designed to act as an MRI responsive probe for imaging the activity of the enzyme glutamic acid decarboxylase (GAD) present in neurons. Upon the action of the enzyme, the Gd(III) complex increases its hydration sphere and takes on a residual positive charge that promotes its binding to endogenous macromolecules. Both effects contribute in a synergic way to generate a marked relaxation enhancement, which directly reports enzyme activity and will allow activity detection of GAD positive cells in vitro and in vivo selectively.
- Napolitano, Roberta,Pariani, Giorgio,Fedeli, Franco,Baranyai, Zsolt,Aswendt, Markus,Aime, Silvio,Gianolio, Eliana
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p. 2466 - 2477
(2013/05/08)
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- An access to aza-Freidinger lactams and E-locked analogs
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Freidinger lactams, possessing a peptide bond configuration locked to Z, are important key elements of conformationally restricted peptidomimetics. In the present work, the CαHi+1 unit has been replaced by N, leading to novel aza-Fre
- Ottersbach, Philipp A.,Schmitz, Janina,Schnakenburg, Gregor,Gütschow, Michael
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supporting information
p. 448 - 451
(2013/04/11)
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- Synthesis of carbosilane dendritic wedges and their use for the construction of dendritic receptors
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A divergent route for the synthesis of carbosilane wedges that contain either a bromine or amine as focal point has been developed. These new building blocks enable the construction of various core-functionalized carbosilane dendrimers. As a typical example carbosilane dendrimers up to the third generation containing a N,N′,N″-1,3,5-benzenetricarboxamide core (G1-G3) have been synthesized. This new class of molecules has been studied as host molecules and they have been found to bind protected amino acids as guest molecules via hydrogen bonding interactions. A decrease in the association constants was observed for the higher generation dendritic hosts, which is attributed to the increased steric hindrance around the core where the binding site is located. The binding properties of the dendritic host molecules can be tuned by modifying the binding motif at the core of the carbosilane dendrimers. A higher association constant for N-CBZ-protected glutamic acid 1-methyl ester (5) was observed when the third generation N,N′,N″-1,3,5-tris(l- alaninyl)benzenetricarboxamide core-functionalized carbosilane dendrimer (G3′) was used as the host molecule compared to G3. Different association constants for the formation of the diastereomeric G3′·l-5 (K = 295 M-1) and G3′·d-5 (K = 236 M-1) host-guest complexes were observed, pointing to a small enantioselective recognition effect. The difference between the association constants for the formation of the G3′·(l-5)2 and G3′·(d-5)2 host-guest complexes was much more pronounced, K = 37 M-1 versus K = 10 M-1, respectively. The Royal Society of Chemistry 2006.
- Van Heerbeek, Rieko,Kamer, Paul C. J.,Van Leeuwen, Piet N.M.W.,Reek, Joost N.H.
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p. 211 - 223
(2007/10/03)
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- Utility of tetrathiomolybdate and tetraselenotungstate: Efficient synthesis of cystine, selenocystine, and their higher homologues
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Efficient synthesis of cystine, selenocystine, and their higher homologues like homo and bishomo amino acid derivatives from natural amino acid derivatives using tetrathiomolybdate and tetraselenotungstate reagents under mild and neutral conditions is reported. The generality of the reaction has been studied by capping various groups to amino and carboxyl components of canonical amino acids.
- Bhat, Ramakrishna G.,Porhiel, Emmanuel,Saravanan, Vadivelu,Chandrasekaran, Srinivasan
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p. 5251 - 5253
(2007/10/03)
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- Synthesis of (S)-2-amino-8-oxodecanoic acid (Aoda) and apicidin A
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The synthesis of (S)-2-amino-8-oxodecanoic acid, a constituent of the cyclic tetrapeptides, the apicidins, was accomplished under photolytic conditions in the presence of tri-n-butyltin hydride using glutamic acid. This enabled a total synthesis of apicidin A to be completed.
- Mou, Liyuan,Singh, Gurdial
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p. 6603 - 6606
(2007/10/03)
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- An efficient route to the α-methyl ester of L-glutamic acid, and its conversion into cis-5-hydroxy-L-pipecolic acid
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The treatment of the N-benzyloxycarbonyl α-methyl esters of L-glutamine or L-asparagine with tert-butyl nitrite in refluxing acetonitrile results in selective hydrolysis of the amide group, giving optically pure Z-Glu-OMe (74%) or Z-Asp-OMe (88%); these are versatile chiral building blocks, and an efficient synthesis of cis-5-hydroxy-L-pipecolic acid from Z-Glu-OMe is described.
- Adams, David R.,Bailey, Patrick D.,Collier, Ian D.,Heffernan, John D.,Stokes, Stephen
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p. 349 - 350
(2007/10/03)
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- The chemistry of phosphapeptides: Investigations on the synthesis of phosphonamidate, phosphonate, and phosphinate analogues of glutamyl-γ-glutamate
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The synthesis of the phosphonamidate, 1d, and phosphonate, 1e, analogues of a γ-glutamyl peptide are reported. Michaelis-Albuzov reaction with the alkyl halide, 7b, derived from L-glutamic acid, yielded dimethyl phosphonate, 8b. Selective aminolysis of th
- Malachowski,Coward
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p. 7625 - 7634
(2007/10/02)
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- Synthesis of 5-oxo-L-pipecolic acid derivatives by rhodium(II) acetate catalyzed cyclization of diazoketones
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A convenient synthesis of 5-oxo-L-pipecolic acid derivatives is described. The key step involves the rhodium(II) acetate catalysed N-H insertion reaction of diazoketones, which are derived from L-glutamic acid.
- Ko, Kwang-Youn,Lee, Kee-In,Kim, Wan-Loo
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p. 6651 - 6652
(2007/10/02)
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- CHIRAL SYNTHESIS OF 5-HYDROXY-(L)-PIPECOLIC ACIDS FROM (L)-GLUTAMIC ACID
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A stereo- and enantio-specific synthesis of the naturally occuring cis-5-hydroxy-(L)-pipecolic acid (3) is described, starting from Z-(L)-glutamic acid; the key step involves cyclisation of a protected chlorohydrin, and also gives access to trans-5-hydroxy-(L)-pipecolic acid.
- Bailey, Patrick D.,Bryans, Justin S.
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p. 2231 - 2234
(2007/10/02)
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- MONO-ESTERIFICATION OF N-PROTECTED DI-ACIDS ASPARTIC AND GLUTAMIC BY CHLOROFORMATE ACTIVATION
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Mono-esters of N-protected di-acids aspartic and glutamic are prepared by a one-pot activation with alkyl chloroformates or isopropenyl chloroformate and an additionnal alcohol.This process involves the intermediate internal anhydride formation.
- Jouin, P.,Castro, B.,Zeggaf, C.,Pantaloni, A.,Senet, J.P,et al
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p. 1665 - 1668
(2007/10/02)
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- A NOVEL AND EFFICIENT SYNTHESIS OF L-VINYLGLYCINE
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A simple and practical synthesis of the title compound starting with L-glutamic acid is described.
- Hanessian, Stephen,Sahoo, Soumya P.
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p. 1425 - 1428
(2007/10/02)
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- Useful Intermediates for Synthesis of Dicarba Analogues of Cystine Peptides: Selectively Protected α-Aminosuberic Acid and α,α'-Diaminosuberic Acid of Defined Stereochemistry
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Practical procedures are described for synthesis of selectively protected α-aminosuberic acid and α,α'-diaminosuberic acid by the mixed Kolbe electrolytic decarboxylative dimerization of two different carboxylic acids.Stereochemistry is established by the choice of L- or D-glutamic acid precursors.The method is illustrated by the synthesis of α-tert-butyl Nα-Boc-Nα'-Cbz-LL-α,α'-diaminosuberate (6) and α-tert-butyl ω-methyl Nα-Boc-D-α-aminosuberate (10) which can be used directly in the preparation of dicarba and desaminodicarba analogues of cystinepeptides.Although statistically controlled mixtures are produced, facile procedures for isolation of the products have been worked out.No racemization of chiral centers was detected.
- Nutt, Ruth F.,Strachan, Robert G.,Veber, Daniel F.,Holly, Frederick W.
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p. 3078 - 3080
(2007/10/02)
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