Single Diastereomers of Polyhydroxylated 9-Oxa-1-azabicyclo[4.2.1]nonanes from Intramolecular 1,3-Dipolar Cycloaddition of ω-Unsaturated Nitrones
作者:Petra Pádár、Attila Bokros、Gábor Paragi、Péter Forgó、Zoltán Kele、Nicola M. Howarth、Lajos Kovács
DOI:10.1021/jo061503b
日期:2006.10.1
a-1-azabicyclo[4.2.1]nonane has been prepared as the single diastereoisomer 8 from an intramolecular 1,3-dipolar cycloaddition involving 2-(benzyloxy)acetaldehyde and ω-unsaturated hydroxylamine 7 derived from methyl α-d-glucopyranoside. The analogous 8-methoxycarbonyl 9-oxa-1-azabicyclo[4.2.1]nonane was afforded in a similar manner, from methyl d-galactopyranoside and methyl glyoxylate, as a 3:1 mixture
Intramolecular 1,3-dipolar cycloaddition of unsaturated nitrones derived from methyl α-d-glucopyranoside
作者:Petra Pádár、Miklós Hornyák、Péter Forgó、Zoltán Kele、Gábor Paragi、Nicola M. Howarth、Lajos Kovács
DOI:10.1016/j.tet.2005.04.066
日期:2005.7
The intramolecular 1,3-dipolar cycloaddition of unsaturated nitrones derivedfrom methyl α-d-glucopyranoside with 2-furaldehyde has been studied. This cycloaddition was found to afford three 9-oxa-1-azabicyclo[4.2.1]nonane diastereomers in a 3:1:1 ratio [with the principal isomer possessing a (3S,4R,5S,6S,8S) configuration, determined by NMR spectroscopy]. The effects of different Lewis acid catalysts
Stereocontrolled synthesis of polyhydroxylated hexahydro-1H-cyclopent[c]isoxazoles by intramolecular oxime olefin cycloadditions: an approach to aminocyclopentitols
作者:Paul J. Dransfield、Stéphane Moutel、Michael Shipman、Vladimir Sik
DOI:10.1039/a905706d
日期:——
to the newly formed hexahydro-1H-cyclopent[c]isoxazole ring system. The role of the solvent polarity on the diastereochemical outcome of these reactions is briefly discussed. Unsuccessful efforts to extend this chemistry to oximes derived from alk-4-enyl aldehydes are also presented. Finally, it is demonstrated that the hexahydro-1H-cyclopent[c]isoxazoles can be transformed into stereochemically defined
可以将衍生自各种碳水化合物(D-葡萄糖,D-甘露糖,D-半乳糖,D-葡萄糖)的一系列烷基-5-烯基醛转化为相应的肟。这些肟的热解导致通过分子内肟烯烃环加成以良好的产率分离六氢-1 H-环戊[ c ]异恶唑。在这些环加成反应中观察到中等至优异的非对映异构控制水平,这取决于肟前体的精确性质。在最佳情况下,D-葡萄糖衍生的肟4产生六氢-1 H-环戊[ c以]异恶唑5为唯一产品的定量收率。观察到当肟具有与肟碳原子相邻的取代基(OBn或OBz)时,反应显示出优先产生非对映体环加合物的趋势,其中该取代基相对于新形成的hexahydro-1 H处于exo取向-环戊[ c ]异恶唑环系统。简要讨论了溶剂极性对这些反应的非对映化学结果的作用。还提出了未能成功地将这种化学方法扩展到衍生自烷基-4-烯基醛的肟的努力。最后,证明了六氢-1 H-环戊[ c可以将]异恶唑转化为立体化学定义的氨基环戊糖醇。
Metal-graphite reagents in carbohydrate chemistry. 8. The scope and limitations of the use of zinc/silver-graphite in the synthesis of carbohydrate-derived substituted hex-5-enals and pent-4-enals