Intramolecular Metal-Free C(sp<sup>3</sup>)-H Activation Enables a Selective Mono <i>O</i>-Debenzylation of Fully Protected Aminosugars
作者:Andrés G. Santana、Antonio J. Herrera、Concepción C. González
DOI:10.1021/acs.joc.1c01977
日期:2021.12.3
Carbamate-bearing benzylated aminosugars undergo an I2/I(III)-promoted intramolecular hydrogen atom transfer (IHAT) followed by a nucleophilic attack to provide polycyclic structures. Thus, suitably positioned benzyl ethers are surgically oxidized into the corresponding mixed N/O-benzylidene acetals, which can be conveniently deprotected under mild acidic conditions to grant access to selectively O-deprotected
带有氨基甲酸酯的苄基化氨基糖经历 I 2 /I(III) 促进的分子内氢原子转移 (IHAT),然后进行亲核攻击以提供多环结构。因此,适当定位的苄基醚通过外科手术氧化成相应的混合N / O-亚苄基缩醛,可以在温和的酸性条件下方便地对其进行脱保护,从而获得选择性的O-脱保护氨基糖,以便进一步衍生化。该策略的范围已通过一系列呋喃和吡喃支架得到证实。包括 Hammett LFER 和 KIE 分析在内的初步机理研究支持以亲核环化作为速率决定步骤的反应途径。
2-Amino-2-deoxyglycoside Derivatives via Hofmann Rearrangement of 2-Carbamoyl-2-deoxyglycosides
Methyl 2-methoxy- and 2-tert-butoxycarbonylamino-2-deoxyglycosides were obtained from methyl 2-carbamoyl-2-deoxyglycosides via Hofmann rearrangement with sodium methoxide/bromine/methanol or sodium hydroxide/sodium bromite/methanol or lead tetraacetate tert-butyl alcohol/dimethylformamide.