Total synthesis, structure revision, and absolute configuration of (-)-brevenal.
Total synthesis of structure 1 originally proposed for brevenal, a nontoxic polycyclic ether natural product isolated from the Florida red tide dinoflagellate, Karenia brevis, was accomplished. The key features of the synthesis involved (i) convergent assembly of the pentacyclic polyether skeleton based on our developed Suzuki-Miyaura coupling chemistry and (ii) stereoselective construction of the multi-substituted (E,E)-dienal side chain by using copper(I) thiophen-2-carboxylate (CuTC)-promoted modified Stille coupling. The disparity of NMR spectra between the synthetic material and the natural product required a revision of the proposed structure. Detailed spectroscopic comparison of synthetic 1 with natural brevenal, coupled with the postulated biosynthetic pathway for marine polyether natural products, suggested that the natural product was most likely represented by 2, the C26 epimer of the proposed structure 1. The revised structure was finally validated by completing the first total synthesis of (-)-2, which also unambiguously established the absolute configuration of the natural product.
Fuwa
Haruhiko
H
Laboratory of Biostructural Chemistry, Graduate School of Life Sciences, Tohoku University, Aoba-ku, Sendai 981-8555, Japan.
Ebine
Makoto
M
Bourdelais
Andrea J
AJ
Baden
Daniel G
DG
Sasaki
Makoto
M
D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D012680:Sensitivity and Specificity; D013237:Stereoisomerism; D013874:Thiopental / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry
C004316:thiobutabarbital; D013874:Thiopental