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SummaryThe biosynthesis of the benzo [clphenanthridine alkaloids was investigated in a cell suspension culture of Macleaya cordata (papaveraceae). Feeding experiments define the biosynthetic pathway (-)-7,8,13,13 a-tetrahydrocoptisine -+ (-)-cis-Nmethyl-7,8,13,13a-tetrahydrocoptisinium salt 15 + protopine (5) -+ sanguinarine (1) -+ chelirubine (3)+ macarpine (4).Sanguinarine (1) and chelerythrine (2) belong to the benzo [clphenanthridine alkaloids class [I]. These alkaloids occur widely in papaveraceous plants [2]. They have four oxygen functions at the positions 2, 3, 7 and 8. Besides 1 and 2, the alkaloids chelirubine (3), chelirutine, sanguirubine and sanguirutine bearing five oxygen functions at C(2), C(3), C(7), C(8) and C(10) have been isolated from several plants [3]. Macarpine (4) bearing six oxygen functions at C(2), C(3), C(7), C (8), C (10) and C (12) has been also found [4].Although biosynthetic studies on 0,-type alkaloids (sanguinarine and chelerythrine) have been described [5] [6], the biosynthetic route of the 05-and 0,-type alkaloids has been unexplored, presumably due to their poor existence in plants. We now report a biosynthetic investigation on chelirubine (3) and macarpine (4) by using the callus tissues of Macleaya cordata (papaveraceae). Moreover, the opportunity has been taken to investigate in detail the pathway of sanguinarine (1) and chelerythrine (2). A related experiment with the intact plants of Macleaya cordata is also described.The callus tissues of M . cordata were derived from the stem and the root tissue, respectively. Each callus grew to form a mixture of the white and the red-orange colored colonies. The white-type and the red-orange-type colonies were selected visually, and two types of the colonies were subcultured under the same conditions. After subculturing for one year, the alkaloidal fraction of each callus tissue was examined. The alkaloidal components found in our callus tissues always involved the same four alkaloids, sanguinarine (I), chelirubine (3), macarpine (4) and protopine (S), which were also found in the intact plants [7]. Berberine (6), chelerythrine (2) and allocryptopine (7) were not detected in our callus tissues. These results are different from those reported by Neumann et al. [8] or by Furuya et al. 191.

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The free energy of activation for rotation about the C-N bond (ΔG‡Tc) in substituted phenyl and benzyl N,N- dimethylcarbamates was determined by the 13C dynamic n.m.r. method. The ΔG‡Tc value depended linearly on Hammett's σ with positive p. We have separated the substituent effects into inductive and resonance effects by using dual substituent parameter ( d.s.p .) analysis, and found that the resonance effect is more important than the inductive effect for para derivatives, and vice versa for meta derivatives. General trends of electronic substituent effects on barriers to rotation in carbamates and structurally related amides are also discussed. The ortho steric effect was small.

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