Berberine alkaloids synthesis steps

Berberine alkaloids synthesis steps, 295-297 Betaines in Wittig olefinations, 29-30 Bicyclic compounds. See Oligocyclic compounds Bicyclic hydrocarbon derivs. pr., 192 Bicyclo[4.1.0]hepta-2,4-dienes rearr., 334 Bicyclo[2.2.1]heptane derivs. pr., 192... 

Futhermore, the photocyclization of the donor-acceptor pair thioether-imide has already been applied to the synthesis of the berberine alkaloid chilinene as an a-key step [252]. 

A number of papers not related directly to the synthesis of specific alkaloids have appeared. An approach to 9,10-disubstituted and 9,10,11-trisubstituted tetrahydroprotoberberines via the aminobenzylisoquinoline (205) has been developed.212 Treatment of (205) with formaldehyde gave the two isomeric tetracyclic systems (206 R1 = NH2, R2 = OMe and R1 = OMe, R2 = NH2) either of which could be further transformed to deaminated or hydroxy-dimethoxy derivatives. For example, diazotization of (206 R1 = NH2, R2 = OMe) followed by hypophosphorous acid deamination gave (206 RJ = H,R2 = OMe) on the other hand, treatment of the diazotized solution with copper sulphate gave (206 R1 = OH, R2 = OMe) albeit in only 3—7 % yield. A short four-step synthesis [(207) — (210)] of the berberine skeleton has been developed.213... 

A one-step synthesis of the protoberberine alkaloid karachine (18), employing a presumed Mannich reaction of 4-methyl-2-trimethylsilyloxy-2,4-pentadiene with berberine, has been detailed by Stevens and Pruitt.154 It is plausible that the initial step of the one-flask reaction sequence leading to karachine is, in fact, a [4+ + 2] cycloaddition of the quaternary aromatic salt, berberine chloride, with the terminal electron-rich olefin of the silyloxydiene [Eq. (70)]. 

A one-step synthesis of the protoberberine alkaloid karachine (18), employing a presumed Mannich reaction of 4-methyl-2-trimethylsilyloxy-2,4-pentadiene with berberine, has been detailed by Stevens and Pruitt. 

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