19-epi-3-iso-21-oxoajmalicine | 134001-72-2

• 分子结构分类: 有机化合物 - 有机杂环化合物 - 吲哚及其衍生物
• 英文名称: 19-epi-3-iso-21-oxoajmalicine
• CAS: 134001-72-2
• 化学式: C₂₁H₂₂N₂O₄
• 分子量: 366.417
• InChiKey: KWYQFPRETPANEM-RQXAQYCVSA-N

计算性质

• 辛醇/水分配系数(LogP)：
  2.71
• 重原子数：
  27.0
• 可旋转键数：
  1.0
• 环数：
  5.0
• sp3杂化的碳原子比例：
  0.43
• 拓扑面积：
  71.63
• 氢给体数：
  1.0
• 氢受体数：
  4.0

反应信息

• 作为反应物：
  描述：

  19-epi-3-iso-21-oxoajmalicine 在 aluminium hydride 作用下， 以 四氢呋喃 为溶剂， 反应 0.18h， 以32%的产率得到(+/-)-3-iso-19-epiajmalicine
  参考文献：
  名称：

  Unified strategy for synthesis of indole and 2-oxindole alkaloids

  摘要：

  A concise and general entry to representative indole alkaloids of the yohimboid, heteroyohimboid, corynantheoid, and 2-oxindole classes has been developed exploiting a strategy that features intramolecular Diels-Alder reactions for the facile construction of the D/E ring subunits of the target alkaloids. The efficacy of the approach is first illustrated by a two-step total synthesis of the yohimboid alkaloid oxogambirtannine (2) from 22. Thus, the Diels-Alder substrate 25, which was prepared by nucleophilic addition of vinyl ketene acetal 24 to the intermediate N-acyliminium salt formed in situ upon reaction of 22 with 23, was heated in the presence of benzoquinone to give a mixture of diastereoisomeric cycloadducts 26 and 27; these adducts underwent spontaneous oxidation to furnish 2. In another application of the strategy, the [4 + 2] heterocyclization of 34a, which was formed upon nucleophilic addition of 1-[(trimethylsilyl)oxy]butadiene to the N-acyliminium salt generated in situ upon treatment of 22 with crotonyl chloride, afforded a mixture (ca. 9:1) of cycloadducts 35a and 36a. The major adduct 35a was converted to 42a using a general procedure for effecting beta-carbomethoxylation of enol ethers to give vinylogous carbonates. Subsequent reduction of 42a to the heteroyohimboid alkaloids (+/-)-tetrahydroalstonine (3) and (+/-)-cathenamine (4) was achieved by selective delivery of 2 or 1 equiv of hydride, respectively. When 42a was treated with sodium amide, stereoselective beta-elimination ensued to give 49, which was converted by chemoselective hydride reduction into the corynantheoid alkaloid (+/-)-geissoschizine (5). Facile access to alkaloids of the 2-oxindole family was realized by using a new protocol for achieving stereoselective, oxidative rearrangements of beta-carboline N(b) lactams into 3,3-disubstituted 2-oxindoles. Thus, exposure of 42a to tert-butyl hypochlorite followed by acid and silver ion induced rearrangement of the intermediate 3-chloroindolenine gave 50, with only traces of the C(7) epimer being detected. Hydride reduction of 50 gave (+/-)-isopteropodine (6), acid-catalyzed isomerization of which furnished an equilibrium mixture (1:3) of 6 and (+/-)-pteropodine (51). The stereochemical course of the intramolecular hetero-Diels-Alder reaction of 34a to give 35a and 36a as the only isolable cycloadducts was examined by computational analysis. The geometry of the six-atom transition state was established by semiempirical methods by using the standard closed-shell, restricted Hartree-Fock (RHF) version of the AM1 method. With use of this constrained geometry for the six-membered pericyclic array, the overall conformational energies for the four possible transition states 52-55 were minimized by MM2 calculations (MacroModel). The calculated relative energies of these transition states were in the order 52 < 53 < 54 < 55. Since the cyclization of 34a produced only 35a and 36a in an approximately 9:1 ratio via the respective transition states 52 and 53, these calculations correlated qualitatively with the experimental results.

  DOI：

  10.1021/ja00016a036
• 作为产物：
  描述：

  16-decarbomethoxy-19-epi-3-iso-21-oxoajmalicine 在 2,6-二叔丁基-4-甲基吡啶 、 三乙胺 作用下， 以 二氯甲烷 为溶剂， 反应 75.0h， 生成 19-epi-3-iso-21-oxoajmalicine
  参考文献：
  名称：

  Unified strategy for synthesis of indole and 2-oxindole alkaloids

  摘要：

  A concise and general entry to representative indole alkaloids of the yohimboid, heteroyohimboid, corynantheoid, and 2-oxindole classes has been developed exploiting a strategy that features intramolecular Diels-Alder reactions for the facile construction of the D/E ring subunits of the target alkaloids. The efficacy of the approach is first illustrated by a two-step total synthesis of the yohimboid alkaloid oxogambirtannine (2) from 22. Thus, the Diels-Alder substrate 25, which was prepared by nucleophilic addition of vinyl ketene acetal 24 to the intermediate N-acyliminium salt formed in situ upon reaction of 22 with 23, was heated in the presence of benzoquinone to give a mixture of diastereoisomeric cycloadducts 26 and 27; these adducts underwent spontaneous oxidation to furnish 2. In another application of the strategy, the [4 + 2] heterocyclization of 34a, which was formed upon nucleophilic addition of 1-[(trimethylsilyl)oxy]butadiene to the N-acyliminium salt generated in situ upon treatment of 22 with crotonyl chloride, afforded a mixture (ca. 9:1) of cycloadducts 35a and 36a. The major adduct 35a was converted to 42a using a general procedure for effecting beta-carbomethoxylation of enol ethers to give vinylogous carbonates. Subsequent reduction of 42a to the heteroyohimboid alkaloids (+/-)-tetrahydroalstonine (3) and (+/-)-cathenamine (4) was achieved by selective delivery of 2 or 1 equiv of hydride, respectively. When 42a was treated with sodium amide, stereoselective beta-elimination ensued to give 49, which was converted by chemoselective hydride reduction into the corynantheoid alkaloid (+/-)-geissoschizine (5). Facile access to alkaloids of the 2-oxindole family was realized by using a new protocol for achieving stereoselective, oxidative rearrangements of beta-carboline N(b) lactams into 3,3-disubstituted 2-oxindoles. Thus, exposure of 42a to tert-butyl hypochlorite followed by acid and silver ion induced rearrangement of the intermediate 3-chloroindolenine gave 50, with only traces of the C(7) epimer being detected. Hydride reduction of 50 gave (+/-)-isopteropodine (6), acid-catalyzed isomerization of which furnished an equilibrium mixture (1:3) of 6 and (+/-)-pteropodine (51). The stereochemical course of the intramolecular hetero-Diels-Alder reaction of 34a to give 35a and 36a as the only isolable cycloadducts was examined by computational analysis. The geometry of the six-atom transition state was established by semiempirical methods by using the standard closed-shell, restricted Hartree-Fock (RHF) version of the AM1 method. With use of this constrained geometry for the six-membered pericyclic array, the overall conformational energies for the four possible transition states 52-55 were minimized by MM2 calculations (MacroModel). The calculated relative energies of these transition states were in the order 52 < 53 < 54 < 55. Since the cyclization of 34a produced only 35a and 36a in an approximately 9:1 ratio via the respective transition states 52 and 53, these calculations correlated qualitatively with the experimental results.

  DOI：

  10.1021/ja00016a036