Synthetic methods for the preparation of ARQ 501 (beta-Lapachone) human blood metabolites

ARQ 501 (3,4-dihydro-2,2-dimethyl-2H-naphthol[1,2-b] pyran-5,6-dione), a synthetic version of beta-Lapachone, is a promising anti-cancer agent currently in multiple Phase II clinical trials. Promising anti-cancer activity was observed in Phase I and Phase II trials. Metabolism by red blood cells of drugs is an understudied area of research and the metabolites arising from oxidative ring opening (M2 and M3), decarbonylation/ring contraction (M5), and decarbonylation/oxidation (M4 and M6) of ARQ 501 offer a unique opportunity to provide insight into these metabolic processes. Since these metabolites were not detected in in vitro incubations of ARQ 501 with liver microsomes and were structurally diverse, confirmation by chemical synthesis was considered essential. In this report, we disclose the synthetic routes employed and the characterization of the reference standards for these blood metabolites as well as additional postulated structures, which were not confirmed as metabolites.