Enzymatic Cyclization of 22,23-Dihydro-2,3-oxidosqualene into Euph-7-en-3-ol and Bacchar-12-en-3
详细信息 查看全文
- 作者：Ikuro Abe ; Yuichi Sakano ; Hideya Tanaka ; Weiwei Lou ; Hiroshi Noguchi ; Masaaki Shibuya ; and Yutaka Ebizuka
- 刊名：Journal of the American Chemical Society
- 出版年：2004
- 出版时间：March 24, 2004
- 年：2004
- 卷：126
- 期：11
- 页码：3426 - 3427
- 全文大小：53K
- 年卷期：v.126,no.11(March 24, 2004)
- ISSN：1520-5126
文摘
Recombinant 
-amyrin synthase from Pisum sativum converted 22,23-dihydro-2,3-oxidosqualene, a substrate analogue lacking the terminal double bond of 2,3-oxidosqualene, into a 4:1 mixture of euph-7-en-3-ol and bacchar-12-en-3-ol. This is the first demonstration of the enzymatic formation of the baccharene skeleton with a six-membered D-ring. In the absence of the terminal double bond, the proton-initiated cyclization first generated the tetracyclic dammarenyl cation, followed by a backbone rearrangement with loss of H-7
leading to the formation of euph-7-en-3-ol, while D-ring expansion to the baccharenyl cation and subsequent 1,2-hydride shifts with H-12 elimination yielded bacchar-12-en-3-ol. It is remarkable that the formation of the anti-Markovnikov six-membered D-ring did not depend on the participation of the terminal 
-electrons.
-amyrin synthase from Pisum sativum converted 22,23-dihydro-2,3-oxidosqualene, a substrate analogue lacking the terminal double bond of 2,3-oxidosqualene, into a 4:1 mixture of euph-7-en-3-ol and bacchar-12-en-3-ol. This is the first demonstration of the enzymatic formation of the baccharene skeleton with a six-membered D-ring. In the absence of the terminal double bond, the proton-initiated cyclization first generated the tetracyclic dammarenyl cation, followed by a backbone rearrangement with loss of H-7 leading to the formation of euph-7-en-3-ol, while D-ring expansion to the baccharenyl cation and subsequent 1,2-hydride shifts with H-12 elimination yielded bacchar-12-en-3-ol. It is remarkable that the formation of the anti-Markovnikov six-membered D-ring did not depend on the participation of the terminal -electrons.