- An efficient synthesis of l-3,4,5-trioxygenated phenylalanine compounds from l-tyrosine
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A new strategy for the synthesis of l-3,4,5-trioxygenated phenylalanine derivatives from l-tyrosine is developed for the first time. The approach, featuring the transformation of aryl diiodide to bis-phenol via a one-pot procedure including lithiation, boronation, and oxidation, is highly practical. By this robust protocol, N-protected l-3,5-bis(tert-butyldimethylsilyloxy)-4- methoxy-phenylalanine and l-3,4,5-trimethoxy-phenylalanine derivatives were obtained from l-tyrosine in 9 steps with 36-40% overall yields.
- Chen, Ruijiao,Liu, Hao,Liu, Xiubing,Chen, Xiaochuan
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p. 3565 - 3570
(2013/04/24)
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- A convenient catalyst for aqueous and protein Suzuki-Miyaura cross-coupling
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(Figure Presented) A phosphine-free palladium catalyst for aqueous Suzuki-Miyaura cross-coupling is presented. The catalyst is active enough to mediate hindered, ortho-substituted biaryl couplings but mild enough for use on peptides and proteins. The Suzuki-Miyaura couplings on protein substrates are the first to proceed in useful conversions. Notably, hydrophobic aryl and vinyl groups can be transferred to the protein surface without the aid of organic solvent since the aryl- and vinylboronic acids used in the coupling are water-soluble as borate salts. The convenience and activity of this catalyst prompts use in both general synthesis and bioconjugation.
- Chalker, Justin M.,Wood, Charlotte S. C.,Davis, Benjamin G.
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supporting information; experimental part
p. 16346 - 16347
(2010/01/29)
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- Characterization of thyroid hormone receptor α (TRα)-specific analogs with varying inner- and outer-ring substituents
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Analogs of the TRα-specific thyromimetic CO23 were synthesized and analyzed in vitro using competitive binding and transactivation assays. Like CO23, all analogs bind to both thyroid hormone receptor subtypes with about the same affinity; however, modification of CO23 by derivatization of the 3′ position of the outer-ring or replacement of the inner-ring iodides with bromides attenuates binding. Despite lacking a preference in binding to TRα, all analogs display TRα-specificity in transactivation assays using U2OS and HeLa cells. At best, several agonists exhibit an approximately 6-12-fold preference in transactivation when tested with TRα in HeLa cells. One analog, CO24, showed in vivo TRα-specific action in a tadpole metamorphosis assay.
- Ocasio, Cory A.,Scanlan, Thomas S.
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p. 762 - 770
(2008/09/17)
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- Synthesis and structure-function studies of melanocyte stimulating hormone analogues modified in the 2 and 4(7) positions: Comparison of activities on frog skin melanophores and melanoma adenylate cyclase
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The synthesis and purification of several analogues of the melanotropins with amino acid substitutions at the tyrosine-2 and methionine-4(7) positions are reported. The compounds synthesized included [4-norleucine]-α-MSH, [7-norleucine]-β(p)-MSH, [2-3',5'
- Hruby,Sawyer,Yang,Bregman,Hadley,Heward
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p. 1432 - 1437
(2007/10/02)
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