Biosynthesis. Part 24. Speculative incorporation experiments with 1-benzylisoquinolines and a logical approach via C6–C2 and C6–C3 precursors to the biosynthesis of hasubanonine and protostephanine
Abstract
Many possible 1-benzyltetrahydroisoquinolines have been examined as possible advanced precursors of the alkaloids hasubanonine (1) and protostephanine (2) in Stephania japonica plants, but none was incorporated significantly. Administration of various precursor molecules having only one aromatic ring, such as tyrosine, has demonstrated that both alkaloids are derived from two different C6–C2 biogenetic units. The subsequent failure of further 1-benzyltetrahydroisoquinolines and bisphenethylamines to be incorporated suggested the intermediacy of either (a) modified 1-benzylisoquinolines or (b) trioxygenated C6–C2 building blocks. Precursors designed to examine the first possibility, such as 1-benzyl-3,4-dihydroisoquinolines or 1-benzyl-1-carboxytetrahydroisoquinolines, were not incorporated into (1) and (2) whereas two 3′,4′,5′-trioxygenated 2-phenylethylamines were incorporated. These findings allow further delineation of the requirements for later precursors of the alkaloids (1) and (2).
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