Stereodivergent construction of cyclic ethers by a regioselective and enantiospecific rhodium-catalyzed allylic etherification: Total synthesis of gaur acid
Stereodivergent construction of cyclic ethers by a regioselective and enantiospecific rhodium-catalyzed allylic etherification: Total synthesis of gaur acid
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DOI：
10.1002/anie.200460612
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发表时间：
2004-01-01
影响因子：
16.6
通讯作者：
Uraguchi, D
中科院分区：
文献类型：
--
作者：
Evans, PA;Leahy, DK;Uraguchi, D
4893 Angew. 2004，116，4892-4895 www. angewandte。de 2004 Wiley-VCH Verlag GmbH & Co. KGaA，魏因海姆二取代的四氢呋喃存在于这种潜在的生物学重要的试剂中，从而能够确定绝对构型。烯丙醇10通过方案2中概述的三步顺序制备。已知的环氧化物8与由正庚基锂和氰化铜（i）衍生的铜酸盐在788 ℃下区域选择性开环，得到所需的醇9，产率为71%。[13仲醇9的苄基保护，接着对甲氧基苯基的氧化裂解，以76%的产率（两步）提供烯丙醇10。[15]对映体富集的烯丙基碳酸酯12通过烯丙醇rac-11的初始Sharpless动力学拆分，然后将产物（R）-11（！99%ee）（方案3）。[16]立体定向烯丙基醚化在与表2中所列的那些类似的反应条件下进行。[17]用亚磷酸三甲酯改性的威尔金森催化剂和由烯丙醇10衍生的烷氧基铜（i）处理烯丙基碳酸酯12，以69%的产率以优异的区域选择性和对映体特异性得到二烯13。19：1通过NMR光谱，Eq.①]。
4893 Angew. Chem. 2004, 116, 4892–4895 www. angewandte. de 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim disubstituted tetrahydrofuran present in this potentially biologically important agent, and thereby enable the determination of the absolute configuration. The allylic alcohol 10 was prepared by the three-step sequence outlined in Scheme 2. Regioselective ring-opening of the known epoxide 8 with the cuprate derived from nheptyllithium and copper (i) cyanide at À788C, gave the desired alcohol 9 in 71% yield.[13, 14] Benzyl protection of the secondary alcohol 9, followed by oxidative cleavage of the pmethoxyphenyl group, furnished the allylic alcohol 10 in 76% yield (two steps).[15] The enantiomerically enriched allylic carbonate 12 was prepared by an initial Sharpless kinetic resolution of the allylic alcohol rac-11, followed by acylation of the product (R)-11 (! 99% ee) with BOC-ON (Scheme 3).[16]The stereospecific allylic etherification was carried out under analogous reaction conditions to those outlined in Table 2.[17] Treatment of the allylic carbonate 12 with the trimethylphosphite-modified Wilkinson catalyst and the copper (i) alkoxide derived from the allylic alcohol 10, afforded the diene 13 in 69% yield with excellent regioselectivity and enantiospecificity [! 19: 1 by NMR spectroscopy, Eq.(1)].