| Summary: | 碩士 === 國立嘉義大學 === 應用化學系研究所 === 105 === This thesis contains two topics: I. Total synthesis of (‒)-alkaloid 223V and synthetic studies of (+)-alkaloid 205B and (‒)-alkaloid 221I II. Total synthesis of (‒)-isoaltholactone via γ-benzyloxy substituted vinylogous urethane.
Our lab has developed [3,3]-sigmatropic rearrangement of an γ-allyloxyl vinylogous urethane intermediate, has been applied to synthesis (‒)-alkaloid 223V. Tricyclic lactone was reduced to triol, subsequent functionalized to ene-iodide. By the radical cyclization for constructing the indolizidine structure with needed stereochemistry. Finally, lactam was reduced with LAH to complete the total synthesis of (‒)-alkaliod 223V.
Synthesis of (‒)-alkaloid 221I was starting from tricyclic lactone. Tricyclic lactone was reduced to triol, subsequent functionalized to diene. The ring-closing metathesis was used to construct the indolizidine structure.
Synthesis of (+)-alkaloid 205B was starting from tricyclic lactone. Tricyclic lactone was prepared by the reaction of 2,5-disubstituted pyrrolidine and methyl allyl β-keto ester, followed by asymmetric alkylation and epimerization of C6 position with needed stereochemistry. The indolizidine structure was constructed by using ring-closing metathesis of the diene compound.
Vinylogous urethane lactone (VUL) was prepared from the reaction of chiral vinylogous urethane (VU) enolate and trans-cinnamaldehyde. The syn product was reduced by Borch reduction following elimination to provide α,β-unsaturated lactone. Epoxidation and ring then opening under acidic condition afforded final product (‒)-Isoaltholactone.
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