SYNTHETIC STUDIES TOWARDS THE PINGUISANES - SYNTHESIS OF 4-EPI-PINGUISONE
SYNTHETIC STUDIES TOWARDS THE PINGUISANES - SYNTHESIS OF 4-EPI-PINGUISONE
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DOI：
10.1039/p19880000471
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发表时间：
1988-03-01
期刊：
影响因子：
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通讯作者：
HIRSHFIELD, J
中科院分区：
文献类型：
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作者：
BAKER, R;SELWOOD, DL;HIRSHFIELD, J
目前已有两种方法合成了合成平醌和4-外平醌所需的独立骨架。虽然1-甲氧基-3-（三甲基硅氧基）丁-1,3-二烯（Danishefsky' s diene）对2,3,4-三甲基-2-环戊烯-2-烯-1- 1完全不反应，但Diels-Alder在非常高的压力下（13-15 kBar）与反应性更强的亲二酚甲基2,3-二甲基-5-氧环戊烯-1-羧酸盐发生环加成反应，水解后(3R*,3aS*,7aR*)-甲基2,3,3a，7 - a-四氢-3,3 -二甲基-1,5(4H)-二恶英-7 -羧酸盐收率很高。该化合物的结构经x射线衍射证实。二烯的烯酸锂与反应性较强的亲二烯试剂在低温下的反应只产生一个迈克尔加成；然而，所得到的氧酯转化为所需的独立中间体，总体产率很高。模型研究提供了一条途径，当应用于独立中间体时，可以有效地转化为(3R*,3aS*,7aS*)-2,3,3a，7a-四氢-3,3a，7a-三甲基lindene-1,5(4H)-二酮。与二甲基铜酸锂偶联加成得到不需要的外聚体，进一步精化得到4-外聚平胍酮和4-外聚平胍醇。
Two procedures have been developed for the synthesis of the appropriate indene skeleton required for construction of pinguisone and 4-epi-pinguisone. Whereas 1-methoxy-3-(trimethylsiloxy)buta-1,3-diene (Danishefsky''s diene) was completely unreactive towards 2,3,4-trimethyl-2-cyclopent-2-en-1-one, Diels-Alder cycloaddition was found to occur at very high pressure (13-15 kBar) with the more reactive dienophile methyl 2,3-diemthyl-5-oxocyclopent-1-ene-1-carboxylate giving, after hydrolysis, (3R*,3aS*,7aR*)-methyl 2,3,3a,7a-tetrahydro-3,3a-diemthyl-1,5(4H)-dioxoindene-7a-carboxylate in good yield. The structure of this compound was confirmed by X-ray diffraction. Reaction of the lithium enolate of the diene with the more reactive dienophile at low temperature gave one Michael addition only; however, the resulting oxo ester was converted into the desired indene intermediate in a good overall yield. Model studies provided a route which, when applied to the indene intermediate, enabled an efficient conversion to (3R*,3aS*,7aS*)-2,3,3a,7a-tetrahydro-3,3a,7a-trimethylindene-1,5(4H)-dione. Conjugate addition with lithium dimethylcuprate gave the undesired epimer exclusively which on further elaboration gave 4-epi-pinguisone and 4-epi-pinguisanol.