节点文献
油菜甾醇内酯及其类似物侧链部分的立体选择性合成及过渡金属催化反应研究及在合成中的应用
Asymmetric Synthesis of the Side Chains of Brassinolide and Studies on the Transition Metal Catalyzed Reaction and Applying in the Synthses
【作者】 陆丽；
【导师】 梁永民；
【作者基本信息】 兰州大学 ， 有机化学， 2009， 博士
【摘要】 本论文主要以油菜甾醇内酯及其类似物的侧链部分的合成新方法，（4R，5S）-O-Acetyl-Osmundalactone的不对称全合成，铂催化反应研究，共分为三部分：一．构筑油菜甾醇内酯及其类似物的侧链部分1．以手性甾体醛为原料，以手性醛诱导的不对称Aldol反应、羰基α位差向异构化反应以及底物控制的不对称氢化为关键步骤构筑C-22／C-23／C-24连续的3个不对称中心或C-22／C-242个手性中心，成功构筑了油菜甾体化合物的侧链部分，为这几类化合物的合成提供了一条简单易行、方便便宜、收率高、立体选择性好的路线。2．实验发现，强碱性条件下；α-硅氧酮在α位发生Aldol反应时，保护基TBS，TBDPS等会发生1，4-氧氧硅迁移现象。二．（4R，5S）-O-Acetyl-Osmundalactone的不对称全合成以L-乳酸乙酯为原料，以利用Sharpless环氧化反应和2，3-环氧醇的碘代重排反应构筑C-4的不对称中心，通过RCM反应构筑六元内脂环，完成了此化合物的不对称全合成工作。三．Pt催化的反应研究PtCl2催化的1，6-烯炔环异构化伴随炔丙基酯重排反应。一般情况，炔丙基酯在PtCl2的催化下发生1，3-酯重排得到金属联烯，发生Diels-Alder-type反应。1，3-酯重排是关键步骤。
【Abstract】 This thesis mainly aims at the studies on novel construction of the side chains ofbrassinolide and related compounds, and the asymmetric total synthesis of(4R,5S)-O-Acetyl-Osmundalactone, and studies on the platinum catalyzed reaction.It mainly consists of the following three parts:PartⅠ: Novel construction of the brassinolide and related compounds’ sidechains.1. We report here a new method for constructing the side chains of brassinolide fromsteroidal-aldehyde, which is stereoselective and produces high yields. The key stepsof this routes included a highly stereoselective asymmetry aldol reaction induced bythe chiral aldehyde, the epimerization of a position of carbonyl and asymmetryhydrogenation induced by the chiral intermediate.2. Novel phenomenon that the silyl groups migrated fromα-oxygen toβ-oxygen inlithium and sodium aldol reaction ofαposition ofα-silyloxy ketone was observed forthe first time in this paper.PartⅡ: The asymmetric total synthesis of (4R,5S)-O-Acetyl-Osmundalactone.Efficient asymmetric total synthesis of (4R,5S)-O-Acetyl-Osmundalactone has beencarried out in several steps from L-ethyl lactate. The key steps included Sharplessasymmetric epoxidation and RCM reaction.PartⅢ: The platinum catalyzed reaction.A platinum catalyzed cycloisomerization of 1,6-enyne coupling with therearrangement chemistry of propargylic ester has been developed. Most probably,under platinum catalysis, propargylic ester undergoes the 1,3-acyloxy migration to afford metal allene intermediate, which is followed by the Diels-Alder type reaction.1,3-Acyloxy migration is the key step during the transformation.
【Key words】 brassinolide； silyl groups migratation； α-pyrone； RCM； platinum catalyzed reaction； 1,6-enyne；