| Summary: | 碩士 === 國立中興大學 === 化學系所 === 104 === Herein, we hope to propose a flexible and concise intramolecular cyclization strategy for fawcettimine-type Lycopodium alkaloids. In this study, we categorized into two parts: intramolecular silylallene-mediated [3+2] annulation and intramolecular α-keto silylenolether-mediated [3+2]-annulation.
At the first part, we planned to synthesize the main chained-framwork by Michael addition of 3-amino-1-propanol, methyl acrylate, and several functional alternations to give iodo-compound. Subsequent coupling of this alkyl iodide with (+)-polugone derived phenylsulfoxide followed by elimination afford the eliminated structure. For the challenging [3+2] annulation reaction we''ve tested a variety of Lewis acids and found the essential factor for this reaction. Besides, through carefully deprotection control, we''ve successfully altered the amine-mask protecting groups into another by the treatment of amide with ZnBr2 / triethylamine. For the second part we focused on the synthesis of the α-keto silylenolether fragment. Through three kinds of research routes, we''ve found the best method for synthesizing the 2,3-dione fragment by the key Horner-Wadsworth-Emmons (HWE) olefination approach. Then we hoped to synthesize the exo-silylenolether through regioselective O-silylation. After that we hope to couple this keto silylenolether with phenylsulfoxide fragment to give the desired intermediate for Lewis acids mediated intramolecular [3+2] annulation.
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