Enantioselective synthesis of altohyrtin C (spongistatin 2):: Synthesis of the EF-bis(pyran) subunit
Enantioselective synthesis of altohyrtin C (spongistatin 2):: Synthesis of the EF-bis(pyran) subunit
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DOI：
10.1002/anie.199727411
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发表时间：
1997-01-01
影响因子：
16.6
通讯作者：
Coleman, PJ
中科院分区：
文献类型：
--
作者：
Evans, DA;Trotter, BW;Coleman, PJ
方案2. E-环苯砜的合成10. a）TESOTf，2，6-二甲基吡啶; B）DIBALH，-78 ℃; c）6，BF，-Et，O，CH，Cl，-78 ℃; d）Lindlar催化剂，Et，2 H，1-己烯，丙酮; e）CSA，MeOH; f）TBSCI，咪唑，DMF; g）9-BBN。然后是HZOz; h）TMSSPh，ZnI，; i）NaH，BnBr，Bu，NI; j）m-CPBA，NaHCO，. (See参考文献[4]缩写。）保护和酰胺还原得到醛5，将其进行费金选择性刘易斯酸催化（BF，. Et，O）羟醛加成，得到硫酯7（87 Yo; dr= 94：6）。Fukuyama还原为衍生的醛[1，2]和酸催化的脱保护-缩醛化，然后对剩余的仲醇进行甲硅烷基保护，得到E-环甲基缩酮8（81%，三步）。
Scheme 2. Synthesis of E-ring phenylsulfone 10. a) TESOTf, 2, 6-lutidine; b) DIBALH,-78 C; c) 6, BF,-Et, O, CH, CI,,-78 C; d) Lindlar catalyst, Et $ iH, I-hexene, acetone; e) CSA, MeOH; f) TBSCI, imidazole, DMF; g) 9-BBN. then HZOz; h) TMSSPh, ZnI,; i) NaH, BnBr, Bu, NI; j) m-CPBA, NaHCO,.(See ref.[4] for abbreviations.) protection and amide reduction provided aldehyde 5, which was subjected to a Felkin-selective Lewis acid catalyzed (BF,. Et, O) aldol addition with thioketene acetal6 to afford thioester 7 (87 Yo; dr= 94: 6). Fukuyama reduction to the derived aldehyde ['] and acid-catalyzed deprotection-acetalization followed by silyl protection of the remaining secondary alcohol afforded the E-ring methyl ketal8 (81%, three steps).