25 ヒガンバナ科アルカロイドCrinamine,6-Hydroxycrinamine,Criwelline,およびMacronineの合成研究

抄録

Stereoselective total syntheses of Amaryllidaceae alkaloids, crinamine, 6-hydroxycrinamine, criwelline, and macronine which have C_3-α-methoxy group were achieved as follows, starting from the Diels-Alder adduct (12) of 3-(3',4'-methylenedioxyphenyl)-Δ^2-pyrrolin-4,5-dione and butadiene. Borohydride reduction and acetylation of (12) yielded (30). Treatment of (30) with PhSeSePh and N-bromoacetamide in methanol followed by peroxide oxidation and elimination afforded a desired allyl-methyl-ether (40) in about 35% yield. The imino-ether (43) prepared from (40) by Meerwein reagent were smoothly reduced by NaBH_4-SnCl_4・2Et_2O complex in glyme into (20), the common intermediate to the title alkaloids. (±)-Crinamine (6) was obtained by heating the hydrochloride of (42) with formaldehyde. Formylation of (20) and heating of the resulted formate with POCl_3 yielded (45) which on hydrolysis gave (±)-6-hydroxycrinamine (7). Methylation of (45) followed by alkaline treatment afforded (±)-criwelline (9). (±)-Macronine (10) was synthesized via a lactam intermediate (48).