Reticulin sources

Reticuline is also the source of the morphine alkaloids by ortho/para radical coupling. The roles of the two rings are reversed this time and it is quite difficult to see at first how the structures are related. 

The following new sources of alkaloids have been reported Anona muricata, which yielded reticuline 65 Cinnamomum species, from which cinnamolaurine (36 R1 = Me, R2 + R3 = CH2,R4 = H), (+ )-reticuline(37 R = H), and a new... 

New sources for known alkaloids are (+ )-reticuline, Litsea xylanica (Laura-ceae) and Hernandia jamaicensis (Hernandiaceae) (see ref. 87) coclaurine, Sarcopetalum harveyanum Muell. (Menispermaceae) (— )-armepavine, Euony-mus europaeus (Celastraceae) (+ )-armepavine N-metho-salt, Xanthoxylum inerme Koidz. (Fagara boninensis Koidz.) (Rutaceae). ... 

Apparently, the reason that norlaudanosoline (which had never been isolated from any plant source) is easily incorporated is because of the relative nonspecificity of the enzymes of the reticuline pathway (Hartmann, 1991). This nonspecificity contrasts with the high specificity found among the enzymes involved in the synthesis of more complex structures (Hartmann, 1991). 

The conversion of (5)-norcoclaurine to (i )-reticuline, the immediate precursor to oxidative cyclization, clearly requires three methylations ( ), an oxidation, and an isomerization (the latter effected by an oxidation and then a reduction). Thus, as shown in Scheme 13.41, it has been found that (i 5)-norcoclaurine 6-0-methyltransferase (EC 2.1.1.128) effects the methylation of (S)-norcoclaurine through transfer of a methyl group from 5-adenosylmethionine to phenolic hydroxyl at C-6 of (5)-norcoclaurine generating (5)-coclaurine and 5-adenosylhomocysteine. Then, a second methylation, with the same methylation source but now under the influence of the enzyme (5)-coclaurine-A -methyltransferase (EC 2.1.1.140) produces (5)-A -methylcoclaurine. 

The biosynthesis of reticuline from simple sources of carbon can be achieved by combining the artificial BIA synthetic pathway (which converts dopamine to reticuline) and the dopamine fermentation pathway (which consists of the three steps described in the subsections above). Only very recent study on microbial BIA fermentation has been reported using single E. coli cells [24]. In that report, reticuline... 

S)-Scouleiine (73) derived from (S)-reticuline [as (25)] is the source via (S)-stylo-pine (74) for chelidonine (76). Transformation of stylopine (74) to chelidonine (76) occurs with retention of tritium label at C-5 and C-8, but loss of tritium from C-14, and loss of the (pro-S)-hydrogen atoms from C-13 and C-6. In each case proton removal is from the a-face of the biosynthetic intermediates. 

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