Synthese der Theonelladine A, B, C, D und von Niphatesin A

✍ Scribed by Teubner, Achim ;Gerlach, Hans

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 512 KB
• Volume: 1993
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.199319930129

✦ Synopsis

Syntheses of the Theonelladines A, B, C, D and of Niphatesine A

The pyridine alkaloids theonelladine A–D (1–4) and niphatesine (5) of marine origin have been synthesized starting either from 3‐(4,4‐dibromo‐3‐butenyl)pyridine (6) or from 3‐pyridinecarbaldehyde. Reaction of 6 with two equivalents of BuLi gave the lithiated derivative of the alkyne 7, which could be alkylated with 1‐bromo‐10‐(tetrahydro‐2‐pyranyloxy)decane (8) to yield the alkynol 9 after methanolysis. Selective hydrogenation of 9 with Lindlar palladium catalyst gave (Z)‐14‐(3‐pyridyl)‐11‐tetradecan‐1‐ol (11). – Addition of the Grignard reagent of 12‐(benzyloxy)‐1‐bromododecane (13) to 3‐pyridinecarbaldehyde gave 17, which was first oxidized (Swern) to give 18 and then reduced (Wolff‐Kishner) to give 14. Hydrogenolysis of the benzyl ether 14 yielded 15. The alcohol group in 9, 11, and 15 was converted into the tosyloxy group by reaction with tosyl chloride/pyridine. Subsequent reactions of the tosylates 10, 12, and 16 either with an excess of methylamine/ethanol or of ammonia/ethanol gave the pyridine alkaloids 1–5 in high yields as p‐toluenesulfonates.