Chelerythrine synthesis

Scheme 37. Synthesis of chelerythrine (205) and sanguinarine (206) by photocyclization. Reagents a, hv, benzene b, Pd-C, p-cymene c, DDQ, benzene.

Scheme 41. Biomimetic synthesis of chelerythrine (205) and fagaridine (238) via the enamide aldehyde. Reagents a, B2H6 b, H202, NaOH c, PCC d, T1(N03)3, MeOH e, HC1 f, LAH g, MeOH h, NaBH4 i, p-TsOH, toluene j, I2, EtOH.

Synthesis of all four 8,8a-secobenzophenanthridine alkaloids was carried out chiefly by Baeyer-Villiger oxidation of appropriate benzophen-anthridines (Scheme 32). Thus, arnottianamide (206) was obtained from chelerythrine (210) (172,175), iwamide (207) from N-methyldecarine (211) (168,172), integriamide (208) from avicine (212) (171,172), and isoarnottiamide (209) from nitidine (213) (172,175). The proposed mechanism of this reaction (168,172,175) consists of initial attack of the peroxide ion on the C=N+ double bond followed by rearrangement and hydrolysis. 

Chelerythrine. Ninomiya et al. (89) in 1977 applied enamide photocycli-zation to the enamide 68 on their way to total synthesis of homochelidonine. The cyclization did not show any regioselectivity, thus giving two lactams... 

Chelerythrine Intramolecular Heck-type biaryl synthesis [452]... 

In 2008, Jones et cd. disclosed a stoichiometric Rh(III)-mediated reaction of JV-benzylidenemethylamine with dimethyl acetylenedicarboxylate to give the corresponding isoquinolinium salt [52a]. Inspired by this work, in 2012 we developed a Rh(III)-catalyzed one-pot synthesis of isoquinolinium salts 104 from benzaldehydes, primary amines, and internal alkynes by C-H activation and annulation [52b]. This was the first report for the synthesis of isoquinohnium salts by catalytic C-H activation. It is noteworthy that the current procedure was successfully apphed to the total synthesis of isoquinolinone alkaloid oxy-chelerythrine 105 (Eq. (5.99)). In 2013, our group and Huang independently found that various isoquinohnium salts could be synthesized from aryl ketimines, 2-phenyl pyridines, and alkynes under similar reaction conditions, as shown in Eqs. (5.100)-(5.102) [52c-e]. 

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