The 1,1-Dioxobenzo[b]thiophene-2-ylmethyloxycarbonyl (Bsmoc) Amino-Protecting Group
摘要:
Full details are presented for use of the Bsmoc amino-protecting group for both solid phase and rapid continuous solution syntheses. Application to the latter methodology represents a significant improvement over the corresponding Fmoc-based method for rapid solution synthesis due to the opportunity to use water or saturated sodium-chloride solution rather than an acidic phosphate buffer to remove all byproducts, with consequent cleaner phase separation and higher yields of the growing peptide. Comparison of the Bsmoc and Bspoc functions showed that the former, because of steric hindrance, does not suffer from the competitive or premature deblocking observed with the Bspoc system. Because of its incorporation of a styrene chromophore, resin loading of Bsmoc amino acids could be followed as has previously been shown for the Fmoc analogues. Applications of Bsmoc chemistry to peptide sequences incorporating the base sensitive Asp-Gly unit gave less contamination due to aminosuccinimide formation than comparable syntheses involving standard Fmoc chemistry because a weaker or less concentrated base could be used in the deblocking step. Experimental details are presented for building up peptides in solution via the continuous methodology. Deblockings involved the use of insoluble piperazino silica as well as the polyamine TAEA which simplified aqueous separation of the growing, but nonisolated peptide product, from excess acylating agent and other side products formed in the deblocking process. By the appropriate choice of base, one can act selectively at either site of a molecule which incorporates both beta-elimination and Michael acceptor sites as protective units (Bsmoc vs Fm and Fmoc vs Bsm).
Synthesis of Benzosiloles by Intramolecular anti-Hydroarylation via ortho-C–H Activation of Aryloxyethynyl Silanes
摘要:
Straightforward synthesis of benzosiloles was achieved by the invention of Pd/acid-catalyzed intramolecular anti-hydroarylation of aryloxyethynyl(aryl)-silanes via ortho-C-H bond activation. The aryloxy group bound to the ethynyl carbon is the key factor for this transformation.
Functional-Group-Tolerant, Nickel-Catalyzed Cross-Coupling Reaction for Enantioselective Construction of Tertiary Methyl-Bearing Stereocenters
作者:Hanna M. Wisniewska、Elizabeth C. Swift、Elizabeth R. Jarvo
DOI:10.1021/ja4034999
日期:2013.6.19
The first Negishi nickel-catalyzed stereospecific cross-coupling reaction of secondary benzylic esters is reported. A series of traceless directing groups is evaluated for ability to promote cross-coupling with dimethylzinc. Esters with a chelating thioether derived from commercially available 2-(methylthio)acetic acid are most effective. The products are formed in high yield and with excellent stereospecificity
Ruthenium‐Catalyzed Direct Asymmetric Reductive Amination of Diaryl and Sterically Hindered Ketones with Ammonium Salts and H
<sub>2</sub>
作者:Le' an Hu、Yao Zhang、Qing‐Wen Zhang、Qin Yin、Xumu Zhang
DOI:10.1002/anie.201915459
日期:2020.3.23
A Ru-catalyzed directasymmetric reductive amination of ortho-OH-substituted diaryl and sterically hindered ketones with ammonium salts is reported. This method represents a straightforward route toward the synthesis of synthetically useful chiral primary diarylmethylamines and sterically hindered benzylamines (up to 97 % yield, 93->99 % ee). Elaborations of the chiral amine products into bioactive
Copper-catalysed α-selective allylic alkylation of heteroaryllithium reagents
作者:Carlos Vila、Valentín Hornillos、Martín Fañanás-Mastral、Ben L. Feringa
DOI:10.1039/c4ob01896f
日期:——
2-Allyl-substituted thiophenes and furans are synthesised efficiently in a direct procedure using 2-heteroaryllithium reagents and allyl bromides and chlorides catalysed by ligand-free copper(i). The reactions take place under mild conditions, with excellent α-selectivity, high functional group tolerance and good yields for the SN2 products.
METHOD FOR PREPARING BORINIC ACID DERIVATIVES AND NOVEL BORINIC ACID DERIVATIVES
申请人:MANAC INC.
公开号:US20150105562A1
公开(公告)日:2015-04-16
The present invention relates to a method for preparing borinic acid derivatives and novel borinic acid derivatives. The preparing method of the present invention provides borinic acid derivatives of general formula (2):
(Ar
2
B(OH) (2)
wherein
Ar is the same as defined in the description and claims, selectively and in a high yield by reacting a compound of general formula (1):
Ar-M, (1)
wherein
Ar and M are the same as defined in the description and claims, with tri-t-butyl borate and then hydrolyzing the reaction product.
Diphenylparabanic Acid as a Synthon for the Synthesis of α-Diketones and α-Ketocarboxylic Acids
作者:Nobuko Watanabe、Mitsutaka Hamano、Shota Todaka、Takahiro Asaeda、Hisako K. Ijuin、Masakatsu Matsumoto
DOI:10.1021/jo202304x
日期:2012.1.6
Diphenylparabanic acid was found to react with >2 equiv of organolithiums at −78 °C to effectively give the corresponding symmetrical α-diketones. However, upon treatment with 1 equiv of organolithium, the parabanic acid gave mainly 5-substituted 5-hydroxyimidazolidine-2,4-diones. On the other hand, Grignard reagents were less reactive toward the parabanic acid at low temperature, and selectively gave