Sterospecific Syntheses and Spectroscopic Properties of Isomeric 2,4,6,8-Undecatetraenes. New Hydrocarbons from the Marine Brown Alga Giffordia mitchellae. Part IV.
✍ Scribed by Wilhelm Boland; Nora Schroer; Christiane Sieler; Martin Feigel
- Publisher
- John Wiley and Sons
- Year
- 1987
- Tongue
- German
- Weight
- 908 KB
- Volume
- 70
- Category
- Article
- ISSN
- 0018-019X
No coin nor oath required. For personal study only.
✦ Synopsis
Giffordene ( = (22,42,6E,82)-2,4,6,8-~ndecatetraene; 9f) and five stereoisomers are new C , ,HI, hydrocarbons from the marine brown alga G$fordia mitchellae. Their synthesis is based on non-stereoselective Wittig reactions of (E)-2-alkenals with appropriate acetylenic phosphoranes and subsequent chromatographic separation of the resulting (E/Z)-pairs. The uniform enynes ( > 98 % purity) are then stereospecifically reduced to (Z)-alkenes with Zn(Cu/Ag) in aq. MeOH at r.t. 13C-and 'H-NMR data of the new tetraenes are presented. Biosynthetically, giffordene (90 originates from dodeca-3,6,9-trienoic acid via an unstable (3Z,SZ,8Z)-1,3,5,8-~ndecatetraene followed by a thermally allowed antarafacial 1,7-sigmatropic hydrogen shift to the (2Z,4Z,6E,8Z)-isomer 9f.