INHIBITORS OF CHOLESTEROL-BIOSYNTHESIS .1. TRANS-6-(2-PYRROL-1-YLETHYL)-4-HYDROXYPYRAN-2-ONES, A NOVEL SERIES OF HMG-COA REDUCTASE INHIBITORS .1. EFFECTS OF STRUCTURAL MODIFICATIONS AT THE 2-POSITION AND 5-POSITION OF THE PYRROLE NUCLEUS

A novel series of trans-6-(2-pyrrol-l-ylethyl)-4-hydroxypyran-2-ones and their dihydroxy acid derivatives were prepared and evaluated for their ability to inhibit the enzyme HMG-CoA reductase in vitro. A systematic study of substitution at the 2- and 5-positions of the pyrrole ring revealed that optimum potency was realized with the 2-(4-fluorophenyl)-5-isopropyl derivative 8x (Table III), which possessed 30% of the in vitro activity of the potent fungal metabolite compactin (I). A molecular modeling analysis led to the description of a pharmacophore model characterized by (A) length limits of 5.9 and 3.3 A for the 2- and 5-substituents, respectively, as well as an overall width limit of 10.6 Á across the pyrrole ring from the 2- to the 5-substituent and (B) an orientation of the ethyl(ene) bridge to the 4-hydroxypyran-2-one ring nearly perpendicular to the planes of the parent pyrrole, hexahydronaphthalene, and phenyl rings of the structures examined (Figure 3, θ = 80-110°). Attempts to more closely mimic compactin's polar isobutyric ester side chain with the synthesis of 2-phenylpyrroles containing polar phenyl substituents resulted in analogues (Table III, 8m-p) with equal or slightly reduced potencies when compared to the 2-[(unsubstituted or 4-fluoro) phenyl] pyrroles, supporting the hypothesis that inhibitory potency is relatively insensitive to side-chain polarity or charge distribution in this area. © 1990, American Chemical Society. All rights reserved.