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首页> 外文期刊>Chemistry: A European journal >Stereoselective Conjugate Addition of Nitrogen and Carbon Nucleophiles to Sugar-Derived Enones: Synthesis of Sialic Acid Analogues
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Stereoselective Conjugate Addition of Nitrogen and Carbon Nucleophiles to Sugar-Derived Enones: Synthesis of Sialic Acid Analogues

机译：氮和碳亲核试剂向糖衍生的烯酮的立体选择共轭加成：唾液酸类似物的合成

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摘要

The conjugate addition of benzylamine to three polyalkoxy #alpha#, #beta#-enones derived from D-glyceraldehyde, D-erythrose, and D-mannose, whose carbonyls were flanked by the thiazole ring, proceeded with modest to good synselectivity. The resulting polyalkoxy #beta#-amino ketones were converted by ketalization into methyl 1-(2-thiazolyl)-pyranosides that in turn were transformed into 4-amino-3, 4-dideoxy-ulosonic acids by sequential cleavage of the thiazole ring into the formyl group and oxidation of the latter to carboxylate. Thus, starting from the enone derived from D-mannose, the 4-acetamido-nonulosonic acid iso-Neu4Ac, a positional isomer of sialic acid Neu5Ac, was prepared. Because of some unsatisfactory reactions, a more efficient synthesis of iso-Neu4Ac was carried out by the use of trimethylsilyl azide as a nitrogen nucleophile in the initial conjugate addition reaction. Also, in the presence of DBU the addition of nitromethane to the same enones proceeded with good syn-selectivity and chemical yield. The cyclization of the resulting ketones afforded methyl 3-nitromethyl-1-(2-thiazolyl)-pyranosides. Furthermore, the pyranoside derived from the enone incorporating the D-mannose moiety afforded after reduction of the nitro to the amino group and carboxylate generation from the thiazole ring, a 4-acetamidomethyl-3, 4-dideoxy-ulosonic acid, which is a branched one-carbon higher homologue of iso-Neu4Ac.
机译：将苄胺共轭添加到衍生自D-甘油醛，D-赤藓糖和D-甘露糖的三个聚烷氧基＃α＃，＃β＃-烯酮上，它们的羰基侧接噻唑环，适度至良好的选择性。通过缩酮化将所得的聚烷氧基＃β＃-氨基酮转化为甲基1-（2-噻唑基）-吡喃糖苷，然后通过依次将噻唑环裂解成4-氨基-3，4-二脱氧-乌糖酸而将其转化为4-氨基-3，4-二脱氧-乌洛糖酸。甲酰基和后者的氧化成羧酸盐。因此，从衍生自D-甘露糖的烯酮开始，制备了4-乙酰氨基-壬二酸异Neu4Ac，其为唾液酸Neu5Ac的位置异构体。由于某些不满意的反应，在最初的共轭加成反应中，通过使用叠氮化三甲基硅作为氮亲核试剂，可以更有效地合成iso-Neu4Ac。同样，在DBU存在下，将硝基甲烷添加到相同的烯酮中以良好的顺选择性和化学收率进行。所得酮的环化得到甲基3-硝基甲基-1-（2-噻唑基）-吡喃糖苷。此外，在将硝基还原成氨基并由噻唑环生成羧酸盐后，得自掺有D-甘露糖部分的烯酮的吡喃糖苷，它是一种支链的4-乙酰氨基甲基-3，4-二脱氧-乌磺酸。 iso-Neu4Ac的一碳高级同系物。

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