Biosynthetic studies on the tropane ring system of the tropane alkaloids from Datura stramonium

Isotopic labelling experiments have been carried out in Dautura stramonium root cultures with the Following isotopically labelled precursors; [H-2(3)]-, [2-C-13, H-2(3)], [1-C-13, O-18(2)]-acetates, 2H(2)O, [H-2(3)-methyl]-methionine, [2-C-13]-phenyllacetate, [3-H-3]-tropine and [2'-C-13, 3-H-2]-littorine. The study explored the incorporation of isotope into the tropane ring system of littorine 1 and hyoscyamine 2 and revealed that deuterium from acetate is incorporated only into C-6 and C-7, and not into C-2 and C-4 as previously reported. Oxygen-18 was not retained at a detectable level into the C(3)-O bond from [1-C-13, O-18(2)]-acetate. The intramolecular nature of the rearrangement of littorine 1 to hyoscyamine 2 is revealed again by a labelling study using [2'-C-13, 3-H-2]-littorine, [2-C-13]-phenyllactate and [3-H-2]-tropine. (C) 2000 Elsevier Science Ltd. All rights reserved.