Mammalian Alkaloids: O-Methylation of (±)-Norcoclaurine-1-carboxylic Acid and Related Isoquinolines Including (S)- and (R)-Norcoclaurine with 14C-Labeled S-Adenosyl-L-Methionine in Presence of Mammalian Catechol O-Methyltransferase
✍ Scribed by Yasuo Sekine; Cyrns Crevelling; Maureen Bell; Arnold Brossi
- Publisher
- John Wiley and Sons
- Year
- 1990
- Tongue
- German
- Weight
- 500 KB
- Volume
- 73
- Category
- Article
- ISSN
- 0018-019X
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✦ Synopsis
9.1. 90)
(5)-Norcoclaurine-I-carboxylic acid (5) and the derived dihydroisoquinolinone 6 (present as quinonemethide 6a at pH 7) afforded, on methylation with I4C-labeled S-adenosyl-L-methionine in the presence of mammalian catechol 0 methyitransferase, exclusively the 7-0-methylated congeners 7 and 9, respectively. High stereoselectivity of the 0-methylation was observed with (-)-(S)-and (+)-(R)-norcoclaurine (2a and 2b, resp.), affording 80% of 6 -0 -methylated isoquinoline 12 and 20% of the 7-0 -methylated isomer 11 from 2a, and the reversed proportion of 12 and 11 from 2b. Synthesis of the reference amino acid 8 was achieved by Pictet-Spengler condensation of 0-benzyl-protected dopamine 17 with benzyl-protected keto acid 20 ( + 21) followed by methylation with diazomethane ( + 22 + 23) and removal of the protecting groups by acid hydrolysis. It is considered unlikely that amino acids such as 5 constitute important precursors in the biosynthesis of isoquinolines related to reticuline.
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On leave from Tanabe, Seiyaku Co., Saitama, Japan. This is the first report on the conversion of radiolabeled reticuline by rat-liver homogenates into the morphinandienone alkaloid sinacutinc.