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At least 955 records · Page 53Linked to original sources
PubMed2004

Presentation and detection of azide functionality in bacterial cell surface proteins.

An improved protocol for copper-catalyzed triazole formation on the bacterial cell surface is described. Addition of highly pure CuBr to cells treated with azidohomoalanine (2) leads to ca. 10-fold more extensive cell surface labeling than previously observed. This highly active catalyst allows detection of the methionine analogues azidoalanine (1), azidonorvaline (3), and azidonorleucine (4) in cell surface proteins. Azidoalanine was previously believed to be silent with regard to the cellular protein synthesis machinery.

Alanine↗
PubMed2005

Allenyl azide cycloaddition chemistry. synthesis of pyrrolidine-containing bicycles and tricycles via the possible intermediacy of azatrimethylenemethane species.

Thermolysis of 5-azidoallenes bearing a C(1) methyl group and either an aryl ring or an alkene on C(1) furnishes tricyclic (from the aryl substrates) or bicyclic (from the alkenyl substrates) pyrrolidine products following formal H-CN addition across an intermediate imine. High levels of diastereoselectivity are observed in all cases studied. This reaction cascade presumably passes through unobserved triazoline and azatrimethylenemethane diyl intermediates en route to product.

Alkadienes↗
PubMed1994

Characterization of two taxol photoaffinity analogues bearing azide and benzophenone-related photoreactive substituents in the A-ring side chain.

Taxol is a structurally novel and clinically effective antitumor drug, which, unlike other antimitotic agents, induces the assembly of tubulin into microtubules. To characterize the binding site(s) of taxol on the microtubule, taxol-based photoaffinity reagents 1 and 2 bearing photoreactive groups on the A-ring side chain were prepared and evaluated. Taxol analogue 1 exhibits better microtubule assembly activity, greater cytotoxicity toward J774.2 cells, and more specific and efficient photolabeling of the beta-subunit of tubulin than does analogue 2. Therefore, it would appear that 1 is the better candidate for further studies aimed at the characterization of the taxol binding site on the microtubule.

Affinity Labels↗
PubMed2000

Regiochemical studies of the ring expansion reactions of hydroxy azides with cyclic ketones.

The regiochemistry of ring expansions of 2-substituted cyclic ketones using 1,2-azidoethanol and 1,3-azidopropanol was examined. It was determined that the reactions of ketones with an adjacent methyl or ethyl group are generally unselective, but that bulkier substituents lead to preferential migration of the more highly substituted carbon. In addition, it was found that ketones bearing inductively electron-withdrawing substituents (OMe, Ph, Br) undergo selective migration of the less highly substituted carbon. For some substrates, alternative reaction pathways were also identified.

Azides↗
PubMed2001

High-yielding Staudinger ligation of a phosphinothioester and azide to form a peptide.

[figure: see text] The Staudinger ligation can be used to couple a peptide with a C-terminal phosphinothioester to another with an N-terminal alpha-azido group to form a single peptide that contains no residual atoms. Here diphenylphosphinomethanethiol thioesters are shown to give high isolated yields for this transformation. This finding provides precedent for a powerful and versatile new method for the total synthesis of proteins.

Azides↗
PubMed2001

Improved solid-phase peptide synthesis method utilizing alpha-azide-protected amino acids.

[structure: see text]. Pure alpha-azido acids were prepared using an efficient diazo transfer method followed by buffered workup. These building blocks were used to prepare small peptides on Wang resin by two approaches. Peptides prone to diketopiperazine formation were prepared in good yields by coupling acids to resin bound iminophosphoranes during Fmoc-Wang synthesis. The iminophosphoranes can also be hydrolyzed under neutral conditions to provide unprotected amines ready for further coupling.

Amino Acids↗
PubMed2006

Synthesis of functionalized organotrifluoroborates via the 1,3-dipolar cycloaddition of azides.

[reaction: see text] We have successfully prepared potassium azidoalkyltrifluoroborates from the corresponding halogen compounds in 94-98% yields through a nucleophilic substitution reaction with NaN(3). In the presence of various alkynes and Cu(I) as a catalyst, these azidotrifluoroborates easily formed 1,4-disubstituted organo-[1,2,3]-triazol-1-yl-trifluoroborates in 85-98% yields. This method was then developed into a facile one-pot synthesis for the preparation of various organo-[1,2,3]-triazol-1-yl-trifluoroborates using haloalkyltrifluoroborates as the starting materials.

Alkynes↗