作者:Oscar Delgado、H. Martin Müller、Thorsten Bach
DOI:10.1002/chem.200701823
日期:2008.3.7
after metalation to a zinc reagent by another Negishi cross-coupling (48 %). Decisive step of the whole sequence was the macrocyclization to a 29-membered macrolactam, which was conducted as an intramolecular Stille cross-coupling occurring at C-2 of the pyridine core and providing the desired product in 75 % yield. The required stannane was obtained by amide bond formation (87 %) between a complex dithiazole
由N-叔丁氧羰基保护的缬氨酸以最长的20步线性序列合成了有效的抗生素噻唑基肽GE2270 A,总产率为4.8%。关键策略是通过从2,6-二溴-3-碘吡啶开始的连续交叉偶联反应组装2,3,6-三取代吡啶核。通过3-锌的2,6-二溴吡啶的Negishi交叉偶联将完整的Southern片段安装在三噻唑的2-碘噻唑末端(87%)。在通过另一个Negishi交叉偶联金属化成锌试剂后,以截短的2-溴噻唑-4-羧酸叔丁酯形式引入代表分子北部的C-6处的取代基。整个序列的决定性步骤是将大环化成29元大环内酰胺,这是通过发生在吡啶核的C-2处的分子内Stille交叉偶联进行的,以75%的收率提供所需的产物。通过在代表GE2270 A东部的复杂二噻唑片段与3,6-二取代的2-溴吡啶之间的酰胺键形成(87%)获得所需的锡烷。最终步骤包括将丝氨酸-脯氨酸酰胺二肽附着到分子的北部(65%),形成恶唑啉环和甲硅烷基醚脱保护(总体占55%)。