科研之友
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摘要
Herein we described structural insights of a series of analogues to helminthosporin phytotoxins. The key reaction used to prepare the compounds corresponded to the [3 + 4] cycloaddition between the oxyallyl cation generated from 2,4-dibromopentan-3-one and different furans. Their structures were confirmed upon IR, NMR and X-ray diffraction analyses. While bicycles 7, 8 and 9 crystallize in the centrosymmetric monoclinic space group P2(1)/c, compound 10 was solved in the noncentrosymmetric orthorhombic space group P2(1)2(1)2(1). The solid materials obtained were shown to be racemic crystals (7, 8, 9) or racemic conglomerate (10). In all compounds, there is formation of a bicycle featured by fused tetrahydropyranone and 2,5-dihydrofuran rings. They adopt chair and envelope conformations, respectively. Crystal packing of all compounds is stabilized through C-H center dot center dot center dot O contacts. Conformational aspects as well as similarities and differences among the crystal structures of the synthesized analogues are discussed.
- 出版日期2016-2-5
