Biosynthesis of Angular Furanocoumarins: Mechanism and Stereochemistry of the Oxidative Dealkylation of Columbianetin to Angelicin inHeracleum mantegazzianum (Apiaceae)
作者:Volker Stanjek、Wilhelm Boland
DOI:10.1002/(sici)1522-2675(19980909)81:9<1596::aid-hlca1596>3.0.co;2-f
日期:1998.9.9
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-iedoumbelliferone (15) followed by a transfer hydrogenation, which established the cis-orientation of the D-Atom and the 1-hydroxy-1-methylethyl substituent.