The squalestatins: synthesis and biological activity of some C3-modified analogues; replacement of a carboxylic acid or methyl ester with an isoelectronic heterocyclic functionality

Superoxide dismutase mimetics: synthesis and structure-activity relationship study of MnTBAP analogues

Carboxylic ester and amide-substituted analogues of [5,10,15,20-tetrakis(4-carboxyphenyl)-porphyrinato]manganese(III) chloride (MnTBAP) were synthesized and assayed as potential superoxide dismutase (SOD) mimetics. The tetraester analogues 4a and 4b were found to have comparable SOD activity to the known SOD mimetic MnTBAP, while amides 4c-4e exhibited reduced SOD activity. In the substituted methyl benzoate/acid and disubstituted porphyrin series, analogues 12c, 12f, and 12m were found to have comparable to improved SOD activity relative to MnTBAP and analogues 12j, 13a, and 13d exhibited improved activity in both the SOD and thiobarbituric acid reactive species (TBARS) assays relative to MnTBAP.

3-(4-chlorophenyl)-2-(4-diethylaminoethoxyphenyl)-A-pentenonitrile monohydrogen citrate and related analogs. Reversible, competitive, first half-reaction squalene synthetase inhibitors

Squalene synthetase (SQS) catalyzes the head-to-head condensation of two molecules of farnesyl pyrophosphate (FPP) to form squalene. The reaction is unique when compared with those of other FPP-utilizing enzymes, and proceeds in two distinct steps, both of which involve carbocationic reaction intermediates. In this report, we describe the mechanism of action of, and structure-activity relationships within, a series of substituted diethylaminoethoxystilbenes that mimic these reaction intermediates, through characterization of the biochemical properties of 3-(4-chlorophenyl)-2-(4-diethylaminoethoxyphenyl)-A- pentenonitrile monohydrogen citrate (P-3622) and related analogs. As a representative member of this series, P-3622 inhibited SQS reversibly and competitively with respect to FPP (Ki = 0.7 microM), inhibited the enzymatic first half-reaction to the same extent as the overall reaction, exhibited a 300-fold specificity for SQS inhibition relative to protein farnesyltransferase inhibition, inhibited cholesterol synthesis in rat primary hepatocytes (IC50 = 0.8 microM), in cultured human cells (Hep-G2, CaCo-2, and IM-9; IC50 = 0.2, 1.2, and 1.0 microM), and in chow-fed hamsters (62% at 100 mg/kg) without accumulation of post-squalene sterol precursors, and reduced plasma cholesterol in experimental animals. Structure-activity relationships among 72 related analogs suggest that the phenyl residues and central trans-olefin of the stilbene moiety serve as mimics of the three isoprene units of the donor FPP, that substitutions across the central olefin and para-substitutions on the terminal phenyl residue mimic the branching methyl groups of the donor FPP, and that the diethylaminoethoxy moiety of these molecules mimics the various carbocations that develop in the C1-C3 region of the acceptor FPP during reaction. Members of this series of reversible, competitive, first half-reaction SQS inhibitors that show a high degree of specificity for SQS inhibition relative to inhibition of other FPP-utilizing enzymes and other cholesterol synthesis pathway enzymes may serve as useful tools for probing the unique catalytic mechanisms of this important enzyme.

The squalestatins: inhibitors of squalene synthase. Enzyme inhibitory activities and in vivo evaluation of C3-modified analogues

Squalestatin analogues modified at C3 were prepared and evaluated for their ability to inhibit rat liver microsomal squalene synthase in vitro. While the 4,6-dimethyloctenoate ester group at C6 was maintained, a number of modifications to the C3 carboxylic acid were well tolerated. However, in the absence of the C6 ester group, similar modifications to the C3 carboxyl group caused loss of activity. Selected compounds were evaluated for their ability to inhibit cholesterol biosynthesis in vivo in rats 1 and 6 h postadministration. Analogues of squalestatin 1 (S1) modified at C3 were found to possess a shorter duration of effect in vivo which is reflected in their substantially reduced ability to lower serum cholesterol levels in marmosets. Significant cholesterol lowering (up to 62%) for the C3 hydroxymethyl analogue 1b was observed only when this compound was dosed three times a day for 3 days.