New nor-sesquiterpenoids of apparent nardosinane origin from the pacific soft-coral paralemnalia thyrsoides

✍ Scribed by Richard R. Izac; Phillipe Schneider; Margaret Swain; William Fenical

• Book ID: 104220456
• Publisher: Elsevier Science
• Year: 1982
• Tongue: French
• Weight: 215 KB
• Volume: 23
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)86957-9

✦ Synopsis

Two new nor-sesquiterpenoids, 2 and $, apparently related to the nardosinane class, are reported from the alcyonacean soft-coral Paralemnalia thyrsoides collected in Palau. Again using "Difference nOe" techniques, the stereochemistry of the k&o-acetate could be assigned. Irradiation of the bridgehead methyl (C-14) yielded significant enhancement of the protons at C-6 and C-7. This result clearly showed that C-14 is an axial methyl, and that the C-6 and C-7 protons are on the same face of the molecule (C-6 = equatorial, C-7 = axial).

To conclusively interrelate 2 and 5, diketone 2 was converted to 2 in two steps. Forced acetylation of 2 with dimethylaminopyridine resulted in the production of the enol-acetate at C-7, with enolization proceeding, unexpectedly, toward C-8. 9 Assignment of structure 7. for this enol-acetate was reinforced by 13 C NMR (Table 1). Hydrogenation of 2 yielded t5, which was identical in all respects with the natural product.