EXPEDITIOUS SYNTHESIS OF THE POLYPROPIONATE SECTOR OF RIFAMYCIN-S BY REITERATIVE DIENE ALDEHYDE CYCLOCONDENSATION REACTIONS
EXPEDITIOUS SYNTHESIS OF THE POLYPROPIONATE SECTOR OF RIFAMYCIN-S BY REITERATIVE DIENE ALDEHYDE CYCLOCONDENSATION REACTIONS
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DOI：
10.1021/ja00237a037
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发表时间：
1987-02-04
影响因子：
15
通讯作者：
HARVEY, DF
中科院分区：
文献类型：
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作者：
DANISHEFSKY, SJ;MYLES, DC;HARVEY, DF
活化二烯与β - 氧化醛的两种路易斯酸催化的环缩合反应被用于利福霉素S的C19 - C29多聚丙酸酯部分的快速合成。这两个过程在克拉姆 - 费尔金（Cram - Felkin）意义上都具有基本完美的非对映面选择性。第一个过程（见11 + 12 → 13）在四氯化钛的影响下发生，是顺式选择性的。第二个过程（见25 + 35 → 34）由三氟化硼乙醚络合物介导，是反式选择性的（约4.5 : 1）。
Two Lewis acid catalyzed cyclocondensation reactions of activated dienes with .beta.-oxygenated aldehydes are used in a rapid synthesis of the C19-C29 polypropionate sector of rifamycin S. Both processes occur with essentially perfect diastereofacial selectivity in the Cram-Felkin sense. The first process (see 11 + 12 .fwdarw. 13) occurs under the influence of titanium tetrachloride and is cis selective. The second process (see 25 + 35.fwdarw. 34) is mediated by the BF3 etherate and is trans selective (ca. 4.5:1).