Binder RJ, Hatfield MJ, Chi L, Potter PM. Facile synthesis of 1,2-dione-containing abietane analogues for the generation of human carboxylesterase inhibitors.
Eur J Med Chem 2018;
149:79-89. [PMID:
29499489 PMCID:
PMC5863762 DOI:
10.1016/j.ejmech.2018.02.052]
[Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 02/13/2018] [Accepted: 02/14/2018] [Indexed: 12/11/2022]
Abstract
Recently, a series of selective human carboxylesterase inhibitors have been identified based upon the tanshinones, with biologically active molecules containing a 1,2-dione group as part of a naphthoquinone core. Unfortunately, the synthesis of such compounds is complex. Here we describe a novel method for the generation of 1,2-dione containing diterpenoids using a unified approach, by which boronic acids are joined to vinyl bromo-cyclohexene derivatives via Suzuki coupling, followed by electrocyclization and oxidation to the o-phenanthroquinones. This has allowed the construction of a panel of miltirone analogues containing an array of substituents (methyl, isopropyl, fluorine, methoxy) which have been used to develop preliminary SAR with the two human carboxylesterase isoforms. As a consequence, we have synthesized highly potent inhibitors of these enzymes (Ki < 15 nM), that maintain the core tanshinone scaffold. Hence, we have developed a facile and reproducible method for the synthesis of abietane analogues that have resulted in a panel of miltirone derivatives that will be useful tool compounds to assess carboxylesterase biology.
Collapse