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Addition of Dichlorocarbene to Oxyberberine and Berberine
Manikumar, Govindarajan,Shamma, Maurice
, p. 386 - 389 (2007/10/02)
Dichlorocarbene adds to oxyberberine (2) to furnish the key adduct 5.Hydrolysis of 5 in dilute hydrochloric acid yields oxyberberine-13-carboxaldehyde (7).Reduction of adduct 5 with zinc in acetic acid produces 13-methyloxyberberine (11).Alternatively, reduction of 5 with lithium aluminum hydride in hot THF leads to enlargement of ring C with formation of the vinylic chloride 14.A complex transformation occurs when 5 is refluxed in aqueous pyridine, the product being keto lactam 15.Dichlorocarbene in chloroform also adds to berberine (1) to form pentachloro derivative 22.Acid hydrolysis of 22 gives rise to aldehyde 23 which loses hydrogen chloride in the presence of silver oxide to afford dichloro compound 25.Sodium borohydride reduction of 23 produces alcohol 24.
