438461-70-2Relevant academic research and scientific papers
Total Synthesis of (-)-Lepadiformine A Utilizing Hg(OTf)2-Catalyzed Cycloisomerization Reaction
Nishikawa, Keisuke,Kikuchi, Seiho,Ezaki, Shinnosuke,Koyama, Tomoyuki,Nokubo, Haruka,Kodama, Takeshi,Tachi, Yoshimitsu,Morimoto, Yoshiki
, p. 5772 - 5775 (2015)
A cytotoxic marine alkaloid (-)-lepadiformine A (1) possesses a unique structure characterized by the trans-1-azadecalin AB ring system fused with the AC spiro-cyclic ring. In this research, we found that a cycloisomerization reaction from amino ynone 2 t
Total Syntheses of Lepadiformine Marine Alkaloids with Enantiodivergency, Utilizing Hg(OTf)2-Catalyzed Cycloisomerization Reaction and their Cytotoxic Activities
Nishikawa, Keisuke,Yamauchi, Kengo,Kikuchi, Seiho,Ezaki, Shinnosuke,Koyama, Tomoyuki,Nokubo, Haruka,Matsumura, Kunihiro,Kodama, Takeshi,Kumagai, Momochika,Morimoto, Yoshiki
, p. 9535 - 9545 (2017/07/22)
The enantioselective total syntheses of lepadiformine marine alkaloids, azatricyclic natural products isolated from marine tunicates, were completed. These alkaloids have a unique chemical structure characterized by the trans-1-azadecalin (AB ring system) fused with the spirocyclic ring (AC ring system). Here we found that a cycloisomerization reaction from functionalized linear substrates to a 1-azaspiro[4.5]decane framework corresponding to the AC ring in lepadiformines is promoted by a catalytic amount of mercury(II) triflate (Hg(OTf)2). The total syntheses of (?)-lepadiformines A and B were achieved in 28 % and 21 % overall yields, respectively, through the novel cycloisomerization reaction. The syntheses of (+)- and (?)-lepadiformine C hydrochloride salts also enabled us to determine the absolute configuration of natural lepadiformine C. It has been found that a phenomenon of enantiodivergence occurs in lepadiformine alkaloids from a single species of marine tunicate, Clavelina moluccensis. The cytotoxic activities of synthesized lepadiformine hydrochloride salts and their synthetic intermediates were evaluated.
Total synthesis of the tricyclic marine alkaloids (-)-lepadiformine, (+)-cylindricine C, and (-)-fasicularin via a common intermediate formed by formic acid-induced intramolecular conjugate azaspirocyclization
Abe, Hideki,Aoyagi, Sakae,Kibayashi, Chihiro
, p. 1473 - 1480 (2007/10/03)
A very short and efficient enantioselective total synthesis of the tricyclic marine alkaloids (-)-lepadiformine (3), (+)-cylindricine C (1c), and (-)-fasicularin (4) has been developed utilizing the formyloxy 1-azaspiro[4.5]decane 5 as a common intermedia
Stereoselective total syntheses of the racemic form and the natural enantiomer of the marine alkaloid lepadiformine via a novel N-acyliminium ion/allylsilane spirocyclization strategy
Sun, Pu,Sun, Cuixiang,Weinreb, Steven M.
, p. 4337 - 4345 (2007/10/03)
Stereoselective total syntheses of the racemic form and the natural enantiomer of the tricyclic marine alkaloid lepadiformine (6) have been accomplished using a novel intramolecular spirocyclization of an N-acyliminium ion with an allylsilane to form the A/C rings as the key step. Introduction of the hydroxymethyl group at C-13 of the racemic spirocycle 11 was achieved using our methodology for oxidative radical-based remote functionalization of o-aminobenzamides, followed by copper catalyzed addition of Grignard reagent 16 to the N-acyliminium ion intermediate derived from 15. Subsequent Tamao oxidation of silane 17 then afforded the requisite hydroxymethyl compound 19, which was converted to the dimethyl acetal 25 via hydroformylation followed by aldehyde protection. Hydrolysis of the benzamide moiety of 25 and subsequent protection of the primary alcohol gave amino acetal 27. The synthesis was concluded from 27 by a four-step procedure: acid catalyzed ring closure, amino nitrile formation, introduction of the hexyl chain by a Grignard reaction to an iminium salt, and removal of the O-benzyl protecting group to give (±)-lepadiformine (6). The enantioselective total synthesis of 6 started from known optically pure bromide 37, derived from (S)-pyroglutamic acid, and followed a similar sequence involving the key spirocyclization of N-acyliminium ion 42. This synthesis has established the absolute configuration of naturally occurring lepadiformine to be 2(R),5(S),10(S),13(S).
Total synthesis of the natural enantiomer of (-)-lepadiformine and determination of its absolute stereochemistry
Abe, Hideki,Aoyagi, Sakae,Kibayashi, Chihiro
, p. 3017 - 3020 (2007/10/03)
A short synthesis: The naturally occurring (-)-lepadiformine ((-)-3) was prepared in nine steps in 31.4% overall yield. The key step involved the formation of 2 by the spirocyclization of the N-acyliminium ion generated from 1. Furthermore, HPLC analysis
