本論文主要分為兩部分，第一章為研究如何有效地合成 (±)-pterosin A、(R)-pterosin A、(S)-pterosin D、(2S,3S)-pterosin C此四個目標產物。在(±)-pterosin A的合成，以2-bromo-1,3-dimethylbenzene 1做為起始物與-chloropropionyl chloride 進行Friedel-Crafts acylation及 Nazarov cyclization後得indanone 29，再經烷氧醯化及甲基化轉換成-keto ester 50，接著利用Suzuki coupling作為主要步驟來建立6號碳上的支鏈。在經過一些官能基轉換後，完成(±)-pterosin A的合成，共使用9個步驟，總產率為10%。在合成(R)-pterosin A方面，主要利用PLE (porcine liver esterase)對化合物 90 進行不對稱水解，所得到之 chiral compound 91將其轉換成vinyl iodide 95。之後，進行Stille coupling得到diene 97。再將其轉換成diene-ynone，進行分子內Diels-Alder反應(IMDA)及芳香化來完成(R)-pterosin A的合成。第三節報告利用類似(R)-pterosin A的策略合成(2S,3S)-pterosin C，合成以已知物醛 109進行Evans的醛醇反應來合成diene 111，同時建立2號及3號碳上的官能基與立體化學。然後，將其轉換為diene-ynone 113， 並進行IMDA及芳香化後，再去保護來合成(2S,3S)-pterosin C。而 (S)-pterosin D的合成，則以自市面購得之D-(-)-pantolactone 118作為起始物，合成(+)-125。然後，利用Stille coupling製備diene 127，並採用與第三節相同的策略將其轉換成diene-ynone及經過IMDA及芳香化。最後，去除兩個TBS保護來合成(S)-pterosin D。

第二章主要為探討如何有效的合成B型肝炎藥物Entecavir，從已知物193分別合成出相關的中間產物vinyl 195 和 alkyne 204希望未來能透過NHK 環化或自由基環化來完成Entecavir的合成(如下圖所示)。

This thesis consists of two part, the first part deals with the total synthesis of (±)-pterosin A, (R)-pterosin A, (S)-pterosin D and (2S,3S)-pterosin C. The synthesis of (±)-pterosin A started from the reaction of 2-bromo-1,3-dimethylbenzene 1 with -chloropropionyl chloride by using Friedel-Crafts acylation that followed by Nazarov cyclization to afford indanone 29. Indanone 29 is converted to -keto ester 50 by ethoxycarbonylation and methylation. The use of Suzuki coupling reaction is a key step in the synthesis to construct the C6-side chian and then after some functional group transformation -keto ester 50 is converted to (±)-pterosin A. In this synthesis, (±)-pterosin A was accomplished in 9 steps and 10% overall yield. In the synthesis of (R)-pterosin A, PLE (porcine liver esterase) is used to proceed desymmetrization of diester 90 to afford known chiral compound 91. compound 91 is converted to vinyl iodide 95 followed by Stille coupling to afford diene 97. Diene 97 is converted to diene-ynone which could be directly subjected to intramolecular Diels-Alder reaction/aromatization to give (R)-pterosin A. By using the same strategy in the synthesis of (R)-pterosin A, (2S,3S)-pterosin C is synthesized form the known compound aldehyde 109 of Evans’ aldol reaction to give diene 111 with suitable skeleton and chiral center at C2 and C3 of pterosin C. Then, diene 111 was transformed into diene-ynone 113 followed by intramolecular Diels-Alder reaction/aromatization, and the removal protecting groups to afford (2S,3S)-pterosin C. The synthesis of (S)-pterosin D is started form commercially available D-(-)-pantolactone (118). D-(-)-pantolactone (118) is converted to vinyl iodide 125 that possess required functional group and chiral center at C2 and C3 of pterosin D. Vinyl iodide 125 is converted to diene 127 by Stille coupling reaction. Diene 127 is converted to diene-ynone intermediate using a similar synthetic sequence that is reported in section 3. Diene-ynone undergoes intramolecular Diels-Alder reaction/aromatization followed by removal protecting TBS groups to afford (S)-pterosin D.

The second part of this thesis deals with the synthesis of Entecavir. In this part, intemediates were (-)-195 and (-)-204 from epoxy alcohol 193. Cyclization of either intermediate by NHK cyclization or radical cyclization will give triol intermediate as the precursor for the synthesis of Entecavir.

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