WS-9659 B

WS-9659 A, a novel phenazine, produced by a Streptomyces sp., had testosterone 5 alpha-reductase inhibition activity on rat, dog and human prostates. However, WS-9659 A did not show any inhibitory activities for aldose reductase on rabbit lenses and lactate dehydrogenase on pig hearts. WS-9659 A was a competitive inhibitor against testosterone 5 alpha-reductase on rat prostates by use of testosterone as a substrate. Radio receptor binding assay of androgen receptor of rat prostates revealed that WS-9659 A had no affinity for this receptor. WS-9659 A was tested subcutaneously in immature castrated rats to confirm its effect on the growth of the ventral prostates induced by testosterone propionate.

On the basis of spectroscopic and chemical evidence, the structures of WS-9659 A and B isolated as inhibitors of testosterone 5 alpha-reductase from a Streptomyces have been established as 1 and 2, respectively. The reductase inhibitory activities of the derivatives 5 and 6, and degradation products 3 and 8 were considerably less active and substantially inactive, respectively.

In this study, the synthesis of N-alkyl-2-halophenazin-1-ones has been established. Six N-alkyl-2-halophenazin-1-ones, including WS-9659 B and marinocyanins A and B, were synthesized by the direct oxidative condensation of 4-halo-1,2,3-benzenetriol with the corresponding N-alkylbenzene-1,2-diamines. One of the most significant features of the present method is that it can be successfully applied to the synthesis of N-alkyl-2-chlorophenazin-1-ones. The traditional chlorination of N-alkyl-phenazin-1-ones with N-chlorosuccinimide selectively occurs at the 4-position to afford the undesired N-alkyl-4-chlorophenazin-1-ones. Our synthetic route successfully circumvents this problem, culminating in the first chemical synthesis of WS-9659 B. The cytotoxicity of six N-alkyl-2-halophenazin-1-ones and three N-alkylphenazin-1-ones against human promyelocytic leukemia HL-60, human lung cancer A549, and normal MRC-5 cells was evaluated. Among the compounds tested in this study, 2-chloropyocyanin possesses significant selectivity toward A549 cells. The cytotoxic evaluation provides structural insights into the potency and selectivity of these compounds for cancer cells.