金属化合物の関与を鍵反応とした生理活性天然物の合成

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This review deals with total syntheses of biologically active natural products by the use of metal-mediated coupling reactions as key steps. First, we explored the coupling reactions mediated by samarium (II) diiodide (SmI_2), which is a useful versatile one electron reducing reagent. The SmI_2-mediated coupling reactions of N, N-dibenzyl-α-bromoamide and N, N-bis(p-methoxyphenyl)-α-bromoamide with carbonyl compounds gave the corresponding β-hydroxyamides, respectively. Then, oxidative treatment of compound 6c with ceric (IV) ammonium nitrate (CAN) gave d, l-myrmicacine (7b). Synthesis of pyrrolizidine alkaloid pyrrolam A (8), which causes damage to fertilized eggs at a low concentration, was accomplished via the SmI_2-mediated cyclization between a bromoalkyl and ynamide group. Next, (±)-oxerine (15), a monoterpene alkaloid, was synthesized starting from 3-bromopyridine. The synthesis of (±)-oxerine (15) was also carried out via the SmI_2-mediated intramolecular cyclization of γ-ethynyl bromide (40). Next, we focused on the palladiumcatalyzed oxidation of alcohol and tried to expand it to the intermolecular cyclization. As a result, treatment of hydroxyenamines and hydroxy-amines with a palladium catalyst gave the corresponding pyrroles and indoles in moderate to good yields. Finally, the syntheses of three pyrrolidine alkaloids were described. The chromium (II) chloride-mediated coupling reactions of (R)- and (S)-Garner aldehydes (56 and 57) with allyl bromides proceeded with moderate stereoselectivity to afford the corresponding homoallyl alcohols, which were converted to (2R, 3S)-2-hydroxymethyl-3-hydroxypyrrolidine(61), (2R, 3R, 4R)-3-hydroxy-4-methylproline (66), and the enantiomer (77) of (-)-bulgecinine(78).
社団法人日本薬学会の論文
2000-10-01

金属化合物の関与を鍵反応とした生理活性天然物の合成

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