We here report glycosyl sulfoxides appended with an aryl iodide moiety as readily available, air and moisture stable precursors to glycosyl radicals. These glycosyl sulfoxides could be converted to glycosyl radicals by way of a rapid and efficient intramolecular radical substitution event. The use of this type of precursors enabled the synthesis of various complex C‐linked glycoconjugates under mild
Benzylidene Acetal Fragmentation Route to 6-Deoxy Sugars: Direct Reductive Cleavage in the Presence of Ether Protecting Groups, Permitting the Efficient, Highly Stereocontrolled Synthesis of β-<scp>d</scp>-Rhamnosides from <scp>d</scp>-Mannosyl Glycosyl Donors. Total Synthesis of α-<scp>d</scp>-Gal-(1→3)-α-<scp>d</scp>-Rha-(1→3)- β-<scp>d</scp>-Rha-(1→4)-β-<scp>d</scp>-Glu-OMe, the Repeating Unit of the Antigenic Lipopolysaccharide from <i>Escherichia</i> <i>h</i><i>ermannii</i> ATCC 33650 and 33652
作者:David Crich、Qingjia Yao
DOI:10.1021/ja048070j
日期:2004.7.1
donors bearing a carboxylated donor on O3 is a highly alpha-selective mannosyl and, after radicalfragmentation, alpha-d-rhamnosyl donor. Using this stereoselective glycosylation/radical-fragmentation approach, a concise synthesis of the title tetrasaccharide is realized in which both the beta-d- and alpha-d-rhamnopyranosyl units are obtained in a single step by a double radicalfragmentation of the modified
α-Ketenyl radical intermediates in the synthesis of propellanes. A formal synthesis of modhephene
作者:Benoît De Boeck、Gerald Pattenden
DOI:10.1016/s0040-4039(98)01480-4
日期:1998.9
A tandem transannulation - cyclisationsequence from a cyclootenyl substituted α-ketenyl radical intermediate, viz1, is used as the basis of a new, formal, synthesis of the naturally occurring triquinane modhephene 2.
Pinnigorgiols B and E are 9,11-secosteroids with a unique tricyclic γ-diketone framework. Herein, we report the first synthesis of these natural products from inexpensive, commercially available ergosterol. This synthesis features a semipinacol rearrangement and an acyl radical cyclization/hemiketalization cascade; the latter efficiently assembled the tricyclic γ-diketone skeleton, with two rings and
Pinnigorgiols B 和 E 是 9,11-secosteroids,具有独特的三环 γ-二酮框架。在此,我们报告了从廉价的市售麦角甾醇首次合成这些天然产物。该合成具有半频哪醇重排和酰基自由基环化/半缩酮化级联反应;后者有效地组装了三环γ-二酮骨架,一步形成了两个环和三个连续的立体中心。
From Ketenimines to Ketenes to Quinolones: Two Consecutive Pseudopericyclic Events
[reaction: see text] N-[2-(Alkyl- or arylthio)carbonyl]phenyl ketenimines undergo cyclization under mild thermal conditions to afford 2-alkyl(aryl)thio-3H-quinolin-4-ones by means of the 1,5-migration of the alkyl(aryl)thio group from the carbonyl carbon to the central carbon atom of the ketenimine fragment followed by the 6pi-electrocyclization of the resulting vinyliminoketene. These 1,5-migration