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Biosynthesis of Angular Furanocoumarins: Mechanism and Stereochemistry of the Oxidative Dealkylation of Columbianetin to Angelicin in Heracleum mantegazzianum (Apiaceae)
Author(s) -
Stanjek Volker,
Boland Wilhelm
Publication year - 1998
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/(sici)1522-2675(19980909)81:9<1596::aid-hlca1596>3.0.co;2-f
Subject(s) - chemistry , apiaceae , stereochemistry , alkylation , oxidative phosphorylation , biosynthesis , mechanism (biology) , botany , biochemistry , gene , catalysis , philosophy , epistemology , biology
Deuterium‐labelled 5‐fluorocolumbianetin 13 was synthesized as a metabolic probe to examine the stereochemical course of the bioconversion of (+)‐columbianetin ( 12 ) into the angular furocoumarin angelicin ( 5 ). In leaves of Heracleum mantegazzianum , oxidative dealkylation of the specifically deuterated fluorocolumbianetin 13 proceeded by syn ‐elimination of a D‐atom, from C(9), and the vicinal 1‐hydroxy‐1‐methylethyl substituent, yielding 5‐fluoroangelicin ( 23 ). This matches the stereochemical course of the related reaction converting (+)‐marmesin ( 10 ) into the linear furocoumarin psoralen ( 1 ). Key steps in the synthesis of 5‐fluorocolumbianetin ( 13 ) were the copper‐catalysed alkynylation/cyclization of 5‐fluoro‐8‐iodoumbelliferone (15 ) followed by a transfer hydrogenation, which established the cis ‐orientation of the D‐Atom and the 1‐hydroxy‐1‐methylethyl substituent.