- A combined pathway for the synthesis of nitidine family alkaloids
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Three related alkaloids, oxynitidine, nitidine and 5,6-dihydronitidine, have been afforded by the new synthetic protocols. In this approach, the Ni-catalyzed annulation reaction is indicated as the key step to construct the isoquinolinone core structure. The subsequent transformations lead to the target alkaloids.
- Pallikonda, Gangaram,Hsieh, Chang-Yu,Su, Haw-Lih,Hsieh, Jen-Chieh
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p. 5399 - 5407
(2019/11/03)
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- Expeditious approach to pyrrolophenanthridones, phenanthridines, and benzo[ c ]phenanthridines via organocatalytic direct biaryl-coupling promoted by potassium tert -butoxide
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A methodology involving a "transition metal-free" intramolecular biaryl-coupling of o-halo-N-arylbenzylamines has been developed in the presence of potassium tert-butoxide and an organic molecule as catalyst. The reaction appears to proceed through KOtBu-promoted intramolecular homolytic aromatic substitution (HAS). Interestingly, this biaryl coupling also works in the presence of potassium tert-butoxide as sole promoter. On extending our approach further, we found that N-acyl 2-bromo-N-arylbenzylamines undergo a one-pot N-deprotection/biaryl coupling followed by oxidation, thus offering an expeditious route to the phenanthridine and benzo[c]phenanthridine skeletons. The strategy has been applied to a concise synthesis of Amaryllidaceae alkaloids viz. oxoassoanine (1b), anhydrolycorinone (1d), 5,6-dihydrobicolorine (2d), trispheridine (2b), and benzo[c]phenanthridines alkaloids dihydronitidine (3b), dihydrochelerythidine (3d), dihydroavicine (3f), nornitidine (3h), and norchelerythrine (3j).
- De, Subhadip,Mishra, Sourabh,Kakde, Badrinath N.,Dey, Dhananjay,Bisai, Alakesh
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p. 7823 - 7844
(2013/09/12)
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- Gold(I)-catalyzed tandem reactions initiated by hydroamination of alkynyl carbamates: Application to the synthesis of nitidine
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(Chemical Equation Presented) As a convenient and direct synthesis of 1,2-dihydroisoquinolines, the gold(I)-catalyzed intramolecular hydroamination of (2-alkynyl)benzyl carbamates has been developed. The reaction with cationic gold(I) complex [AuCl(PPh3)/AgNTf2] proceeded at room temperature, giving the desired 6-endo adducts. The addition of alcohol efficiently promoted the reaction, and the amount of the catalyst could be reduced to 1 mol %. However, the alkynes bearing either an electron-deficient aryl group or an alkyl group resulted in predominant production of 5-exo adducts. In such cases, use of a bulky gold catalyst, AuCl[(o-biPh)( tBu)2P]Cl/AgNTf2, improved the regioselectivity, giving the 6-endo adducts in better yields. Furthermore, the hydroamination of alkynyl carbamates bearing an acetal or enone was successfully applied to the concise synthesis of tetracyclic heterocycles such as nitidine via the single catalyst-mediated tandem cyclization which consists of a condensation or a Michael addition of the resulting enecarbamates.
- Enomoto, Taro,Girard, Anne-Lise,Yasui, Yoshizumi,Takemoto, Yoshiji
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supporting information; experimental part
p. 9158 - 9164
(2010/03/02)
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- TRANSFORMATION OF PROTOBERBERINES INTO BENZOPHENANTHRIDINES A NOVEL AND EFFICIENT SYNTHESIS OF ANTITUMOR BENZOPHENANTHRIDINE ALKALOIDS, FAGARONINE AND NITIDINE
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Antileukemic benzophenanthridine alkaloids, fagaronine (1a) and nitidine (1c) were synthesized from the corresponding protoberberines through C6-N bond fission and subsequent cyclization between C6 and C13 position of the protoberberines.
- Hanaoka, Miyoji,Yamagishi, Hiroshi,Marutani, Mari,Mukai, Chisato
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p. 5169 - 5172
(2007/10/02)
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