Thesmar P, Baudoin O. Efficient and Divergent Total Synthesis of (-)-Epicoccin G and (-)-Rostratin A Enabled by Double C(sp
3)-H Activation.
J Am Chem Soc 2019;
141:15779-15783. [PMID:
31556609 DOI:
10.1021/jacs.9b09359]
[Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Dithiodiketopiperazines are complex polycyclic natural products possessing a variety of interesting biological activities. Despite their interest, relatively few total syntheses have been completed. We herein report the enantioselective, scalable, and divergent total synthesis of two symmetrical pentacyclic dithiodiketopiperazines, (-)-epicoccin G and (-)-rostratin A. A common intermediate was synthesized on a multigram scale from inexpensive, commercially available starting materials using an enantioselective organocatalytic epoxidation and a double C(sp3)-H activation as key steps, with the latter allowing the efficient simultaneous construction of the two five-membered rings. In addition to the cis,cis-fused target (-)-epiccocin G, the more challenging (-)-rostratin A, possessing two trans ring junctions, was obtained for the first time on a 500 mg scale through the optimization of each step and validation on multigram quantities. Both natural products were synthesized with high overall yields (13-20%). This study should facilitate access to this fascinating and yet understudied family of biologically active natural products.
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