作者:Feng Zhu、Eric Miller、Shuo-qing Zhang、Duk Yi、Sloane O’Neill、Xin Hong、Maciej A. Walczak
DOI:10.1021/jacs.8b11211
日期:2018.12.26
We report a stereoretentive cross-coupling reaction of configurationally stable nucleophiles with disulfide and N-sulfenylsuccinimide donors promoted by Cu(I). We demonstrate the utility of this method in the synthesis of thioglycosides derived from simple alkyl and aryl thiols, thioglycosides, and in the glycodiversification of cysteine residues in peptides. These reactions operate well with carbohydrate
Reversal of Anomeric Selectivity with O-Glycosyl Trichloroacetimidates as Glycosyl Donors and Thiols as Acceptors Under Acid/Base Catalysis
作者:Amit Kumar、Richard R. Schmidt
DOI:10.1002/ejoc.201200138
日期:2012.5
Borontrifluoride or trimethylsilyl trifluoromethanesulfonate catalysed the generation of thioglycosides from O-glucopyranosyl or O-galactopyranosyl trichloroacetimidates and thiols giving mainly or exclusively α-thioglycosides. However, the same reactions with phenylboron difluoride as catalyst are highly β-selective. An SN2-type reaction course under acid/base catalysis is invoked by these and previous
Anomeric Thioglycosides Give Different Anomeric Product Distributions under NIS/TfOH Activation
作者:Helle H. Trinderup、Tatjana L. P. Sandgaard、Line Juul-Madsen、Henrik H. Jensen
DOI:10.1021/acs.joc.1c03001
日期:2022.3.18
The reaction of a series of anomeric thioglycosides with various glycosyl acceptors and N-iodosuccinimide/catalytic triflic acid was investigated with respect to reactivity and anomeric selectivity. In general, β-configured donors were found to give a more β-selective reaction outcome compared to their α-configured counterparts. The relative reactivity of various thioglycosides was measured through
作者:Bhavesh Deore、Joseph E. Ocando、Lan D. Pham、Carlos A. Sanhueza
DOI:10.1021/acs.joc.2c00222
日期:2022.5.6
aglycone-derived thiyl radicals (RS•). In contrast, aryl glucosides’ Ep values exhibit excellent correlations with the aryl substituents’ Hammett parameters (σ+) and the ArS• RSEs, evidencing the inherent stability of the reactive radical intermediate as the primary factor controlling aryl glucoside’s electrochemical reactivity. The reactivity differences between alkyl and aryl S-glucosides also extend to the protective
一系列烷基和芳基S-葡糖苷的伏安研究揭示了烷基S-葡糖苷对阳极氧化的反应模式,并发现与芳基衍生物的趋势存在显着差异。烷基S-葡糖苷的氧化电位,本文由方波伏安峰电位( E p )估计,取决于苷元的空间特性。被大体积基团取代的糖苷在电压比带有小糖苷配基的那些的值更正的电压下表现出E p值。在所有分析的烷基系列中观察到的这种关系由E p之间的良好线性相关性证明和各个烷基取代基的 Taft 空间参数 ( ES )。此外,苷元的空间特性作为主要反应性调节剂的作用得到了E p与苷元衍生的硫基自由基 (RS•) 的自由基稳定能 (RSE) 之间较差相关性的支持。相比之下,芳基葡糖苷的E p值与芳基取代基的 Hammett 参数 (σ+) 和 ArS• RSE 表现出极好的相关性,证明了活性自由基中间体的固有稳定性是控制芳基葡糖苷电化学反应性的主要因素。烷基和芳基S-葡糖苷之间的反应性差异也延伸到保护基团对EP
A practical synthesis of α-d-Manp-(1→3)-α-d-Manp-(1→2)-[α-d-Glcp-(1→3)]-α-d-Manp-(1→2)-α-d-Manp-(1→2)-α-d-Manp, an O-specific heterohexasaccharide fragment of Citrobacter braakii O7a, 3b, 1c
作者:Langqiu Chen、Fanzuo Kong
DOI:10.1016/s0008-6215(03)00381-1
日期:2003.10
An O-specific heterohexasaccharide fragment of Citrobacter braakii O7a, 3b, 1c, alpha-D-Manp-(1-->3)-alpha-D-Manp-(1-->2)-[alpha-D-Glcp(1-->3)] alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->2)-alpha-D-Manp was synthesized as its methyl glycoside. Acetylation of allyl 4,6-O-benzylidene-alpha-D-mannopyranoside, followed by debenzylidenization and benzoylation gave allyl 2,3-di-O-acetyl-4,6-di-O-benzoyl-alpha-D-mannopyranoside (3), and subsequent deacetylation of 3 with CH3COCl-MeOH gave the monosaccharide acceptor 4. Condensation of isopropyl 2,3,4,6-tetra-O-benzyl-1-thio-beta-D-glucopyranoside (6) with 4 selectively afforded the alpha-(l-->3)-linked disaccharide 7. Condensation of 7 with the (1-->3)-linked disaccharide donor 9, followed by deallylation and trichloroacetimidation, afforded the tetrasaccharide donor 12. Coupling of 12 with disaccharide acceptor 13, followed by debenzylation and deacylation, furnished the target heterohexasaccharide 16. (C) 2003 Elsevier Ltd. All rights reserved.