Synthesis of an antitumor active chelerythrine type alkaloid using Claisen rearrangement of a propargyl ether

1. 芳基丙炔醚在CsF存在下的Claisen重排：我们发现在CsF存在下丙炔醚(1)的Claisen重排很容易制备，只得到呋喃(3)而不得到吡喃(2)。用-萘酚衍生物(4)对这一新反应进行了详细的研究。在呋喃环的形成过程中发现了以下事实：(a)溶剂为PHNET_2。(b)除CsF外，其他添加剂不起作用。(c)催化量的脑脊液就足够了，但实际上大约需要等量的脑脊液。在含CsF的PhNEt_2中加热5__-、6__-和7__-缩醛，分别得到相应的呋喃，产率较高，表明反应的普遍性。呋喃环的裂解：以7__-衍生的呋喃(8)作为呋喃环裂解反应的模型化合物。用化学计量量的OsO_4、NaIO_4和dil连续处理8__-。NaHCO_3以满意的产率提供了所需的水杨醛(9)。车车草碱（11）的合成：以3__-为原料，采用上述方法制备醛（10）。用TsOH处理10__-甲基醚导致脱保护和环化生成车车菊啉（11）。我们成功地合成了一种车车菊型生物碱。卡

1. Claisen Rearrangement of Aryl Propargyl Ether in the Presence of CsF: We found that Claisen rearrangement of the propargyl ether (1) in the presence of CsF , easily prepared, gave only the furan (3) but not the pyran (2) . This new reaction was examined in detail using the -naphthol derivative (4). The following facts were found on formation of a furan ring: (a) The best solvent was PHNET_2. (b) Other additives ex-cept CsF could not act. (c) A catalytic amount of CsF was enough, but practically about equimolar amount of it was needed. Heating 5__-, 6__- and the acetal of 7__- in PhNEt_2 containing CsF gave the corresponding furans in good yields, respectively, indicating generality of the reaction.KA2. Cleavage of the Furan Ring: The furan (8) derived from 7__- was used as a model compound for cleavage reaction of a furan ring. Successive treatment of 8__- with a stoichiometric amount of OsO_4, NaIO_4, and dil. NaHCO_3 aq. provided the desired salicylaldehyde (9) in satisfactory yield.3. Synthesis of Chelerythrine (11): The aldehyde (10) was prepared from 3__- using the method mentioned adove. Treatment of the methyl ether of 10__- with TsOH resulted in deprotection and cyc-lization to give chelerythrine (11). We succeeded in synthesizing a chelerythrine type alkaloid.KA