59 Intramolecular Basic Acylationを用いたフェノール性抗腫瘍Benzo[c]phenanthridine Alkaloidの合成法の確立

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Nonphenolic 2-aryl-1-tetralone derivatives (VII), which are key intermediates for syntheses of antileukemic benzo[c]phenanthridine alkaloids (XI), could be prepared through the synthetic sequence involving cyclization of 2,4-diarylbutyric acid derivatives (VI). (Chart 1) Fagaronine (2), an antileukemic phenolic benzo[c]phenanthridine alkaloid, was prepared by this method using an ^iPrO group for protection of its phenol group. However, in other cases, the ^iPrO group was cleaved under the same condition, refluxing with POCl_3 in CHCl_3. We found that the desired nonphenolic tetralones (8a, 8b, 8c and 8d) having ^iPrO or BzlO group could be prepared by refluxing in CH_3CN with POCl_3 in the presence of K_2CO_3 without formation of the corresponding phenolic tetralones. The plausible mechanism for this cyclization has been proposed. (Chart 3) Two synthetic specimens of the phenolic oxybases (5 and 6) were synthesized from the ^iPrO-tetralone (8b and 8c). The naturally occurring oxyterihanine was structurally established as the formula (5). Two quaternary bases, terihanine (3) and isoterihaine (4), were also prepared for cytotoxic activity test. (Chart 4 and 5) Success of synthesis of the phenolic formamide (14f) give a hint to study on development of our synthetic sequence to provide a general method for chelerythrine type alkaloid (20) as follows. i) Claisen rearrangement of the propargyl ether of the formamide (14f), ii) cleavage of the resulting benzofuran (23) to o-acetoxybenzaldehyde derivative (24), and so on. (Chart 6)
天然有機化合物討論会の論文
1986-09-09

59 Intramolecular Basic Acylationを用いたフェノール性抗腫瘍Benzo[c]phenanthridine Alkaloidの合成法の確立

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