Abstract
AbstractO‐Methylation of the optically active 3′‐hydroxycoclaurines 3a and 3b and of the N‐methylated analogs 5a,b with S‐adenosyl‐L‐[methyl‐14C]methionine in presence of mammalian COMT was investigated in vitro. The N‐unsubstituted (1S)‐ and (1R )‐isomers 3a and 3b, respectively, afforded almost equal amounts of the corresponding N‐norreticuline 4 and N‐nororientaline 19, besides two unknown by‐products (see Fig. and Table 1). The N‐methylated (1S)‐isoquinoline 5a, on the other hand, afforded largely (S)‐orientaline ((S)‐19), while an almost equal mixture of (R)‐reticuline (6b) and (R)‐orientaline ((R)‐19) was obtained from the (1R)‐enantiomer 5b. The isoquinolines 3a,b and 5a,b were prepared by a Bischler‐Napieralski cyclization yielding O‐benzyl‐protected isoquinoline 10 (Scheme 1). The optical resolution of 10 was accomplished with 2′‐bromotartranilic acid. The N‐methylated isoquinolines were prepared by N‐formylation of 10a,b and reduction of the formamides 13a,b with diborane (→ 14a,b). Deblocking of the benzyl‐ether moieties of 10a,b and 14a,b was accomplished by catalytic hydrogenation in presence of HCl, affording directly 3a,b·HCl and 5a,b·HCl, respectively.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have