Studies on the chemical constituents of rutaceous plants. L. Development of a versatile method for the synthesis of antitumor-active benzo[c]phenanthridine alkaloids. (2). Preparation of 2-aryl-1-tetralone derivatives

Article abstract of DOI:10.1248/cpb.31.3039

The synthetic pathway from 2,4-bisaryl-4-oxobutyramide (3) to 2-aryl-1-tetralone (4), which is the key intermediate in the Robinson synthesis of antitumor-active benzo[c]phenanthridine alkaloids was improved. Treatment of the model keto-amide (3a) under the reported basic conditions gave γ-keto-α,β-unsaturated acid (9) and degradation products. Reduction of the 2,4-bisaryl-4-oxobutyramide (3) with sodium borohydride gave 2,4-bisaryl-4-hydroxybutyramide (16) which could easily be hydrogenolyzed to give 2,4-bisarylbutyramide (15). However, this transformation also tended to give a γ-lactam derivative (17), unfortunately. We succeeded in the direct hydrogenolysis of the 2,4-bisaryl-4-oxobutyramide (3) to the 2,4-bisarylbutyramide (15), which could be hydrolyzed to the corresponding acid (5) without difficulty. The direct hydrolysis of the 2,4-bisaryl-4-oxobutyronitrile (2) to the 2,4-bisaryl-4-oxobutyric acid (6) as reported by Cheng et al. was also examined. Ten 2-aryl-1-tetralones (4) required as starting materials for syntheses of various benzo[c]phenanthridine alkaloids were prepared.

Full text of DOI:10.1248/cpb.31.3039

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