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Synfacts 2016; 12(2): 0111
DOI: 10.1055/s-0035-1561120
Synthesis of Natural Products and Potential Drugs
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Gymnocin-A

Contributor(s):
Erick M. Carreira
,
Christian Ebner
Sakai T, Matsushita S, Arakawa S, Mori K, Tanimoto M, Tokumasu A, Yoshida T, Mori Y * Meijo University, Nagoya, Japan
Total Synthesis of Gymnocin-A.

J. Am. Chem. Soc. 2015;
137: 14513-14516
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Publication History

Publication Date:
19 January 2016 (online)

 
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Key words

gymnocin-A - polycyclic ether - oxiranyl anions

Significance

Gymnocin-A, a polycyclic ether isolated from Karenia mikimotoi in 2002, exhibits strong cytoxicity (IC50 = 1.3 μg/mL) against mouse leukemia cells. Structurally, this natural product is characterized by 14 consecutive ether rings. Thus far, only one total synthesis has been reported (C. Tsukano, M. Sasaki J. Am. Chem. Soc. 2003, 125, 14294). Herein, Mori and co-workers present a strategically different approach, relying on the union of the three fragments G, H, and I by an oxiranyl anion coupling.


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Comment

The presented synthesis is centered around a multi-step coupling protocol uniting two fragments and concomitantly forming two new cyclic ethers in between. Thereby, a tosyl epoxide of type A was deprotonated and reacted with triflate C, generating D. Acid-mediated TMS deprotection, epoxide opening, and ether formation then yielded ketone E. The second ether ring was ultimately formed by acid-mediated hemiacetalization and reduction with Et3SiH.


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