The invention of radical reactions. Part XXXVIII. Homologation of car☐ylic acids with acrylamide and synthetic studies of 3-deoxy-D-arabino-2-heptulosonic acid (DAH) and its 4-epimer
作者:Derek H.R. Barton、Wansheng Liu
DOI:10.1016/s0040-4020(97)00543-7
日期:1997.8
Alkyl radicals generated from O-acyl derivatives of N-hydroxy-2-thiopyridone added onto acrylamide at room temperature to form crystalline 2-(2-pyridylsulfanyl)-car☐amides. Desulfurization of the latter by nickel boride at room temperature afforded primary amides in quantitative yield. 3-Deoxy-D-arabino-2-heptulosonic acid (DAH), its 4-epimer, and their derivatives were effectively synthesized from
Radical-Based Asymmetric Synthesis: An Iterative Approach to 1, 3, 5, ... (2<i>n</i> + 1) Polyols
作者:Philip Garner、James T. Anderson
DOI:10.1021/ol990188v
日期:1999.10.1
[formula: see text] A conceptually novel approach to 1, 3, 5, ... (2n + 1) polyols based on iterative stereo-controlled homologation of chiral hydroxyalkyl radicals is reported. Starting from alpha-keto ester precursors, the general sequence of (1) ketone reduction, (2) auxiliary attachment, (3) saponification, (4) Barton esterification, and (5) radical addition provided the two-carbon homologue in
An application of the Barton ester based radical reactions in carbohydrate chemistry is described. The chain-elongation reaction with ethyl α-trifluoroacetoxy acrylate 2, followed by treatment with phenylhydrazine provided 3-deoxy-α-hydrazono-octulosonates 8a,b, derivatives of KDO and its gluco-isomer in good yield.
The reaction of α-trifluoroacetoxy acrylates and acrylonitriles with carbon radicals formed from carboxylicacids gives adducts that can be transformed into vic-diols, esters, amides, and homoaldehydes in good to high yield. Aldoses can be smoothly degraded to the corresponding nor- or bis-nor compounds using radicalchemistry.
A route to 3-deoxy-4-O-methyl-D-manno-oct-2-ulosonic acid (4-O-methyl-KDO) and its D-gluco isomer derivatives
作者:Zbigniew Pakulski、Aleksander Zamojski
DOI:10.1016/s0040-4020(97)00094-x
日期:1997.3
Methoxymercuration of α, β-unsaturated ketoester 5 (readily obtained from peracetylated D-gluconic acid 1 via Barton ester) led to a separable mixture of KDO derivative 9 and its D-gluco isomer 10.