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1 2.3.4-Tetrahydro-I -(4-hydroxy-3-methoxybenzyl) -7-methoxy-N-methylisoquinolin-8-01 was oxidatively coupled with potassium ferricyanide to give a mixture of diastereoisomeric dienones. Treatment of the mixture with hydrochloric acid in glacial acetic acid gave a product tentatively identified as 1 -(4,6-dihydroxy-3-methoxybenzyl)-l,2,3,4-tetrahydro-7-methoxy-N-methylisoquinolin-8-ol, whereas treatment of the dienones with hydrogen chloride in methanol gave 1,2,3,4-tetrahydro-7-methoxy-N-methyl-l-(3,4,6-trimethoxybenzyl)isoquinolin-8-ol, whose structure was confirmed by unambiguous synthesis. Two essentially different mechanisms for the formation of the latter product were differentiated by carrying out the ring opening in ethanol instead of methanol : the product was then 1 -(4,6-diethoxy-3-methoxybenzyl) -1,2,3,4-tetrahydro-7-methoxy-Nmet hylisoquinolin -8-01.of Chemistry, University College, Cardiff CF1 1 XL A BIOGENETICALLY modelled synthesis of the benzylisoquinoline alkaloid cularine (la) was recently accomplished in Cardiff,lP2 and also in Japan; in both cases this was achieved by oxidative coupling of the phenolic precursor (2a) followed by methylation. We and Kametani 3 ~5 also attempted to synthesise cularine via acid-catalysed rearrangement of the dienones (3a), which were prepared by oxidative coupling of the phenolic precursor (2b), and might also be implicated in the biosynthesis of cularine (la). The acid-catalysed rearrangement of an analogous dienone (3b) to the cularine analogue (lb) had been described previously.6 However in these laboratories attempted rearrangement of the diastereoisomers (3a) in dry methanolic hydrogen chloride gave the l-benzyltetrahydroisoquinoline (2d), whereas by treatment with concentrated sulphuric acid Kametani obtained the aporphine (4). Both results were unexpected, especially

Oxidative Kupplungsreaktion des Diphenols (I) liefert ein Diastereomerengemisch des Die:nons (II), das bei der Behandlung mit HCl in Eisessig das Isochinolinderivat (III) gibt.

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