A New Class of Selective and Potent 7‑Dehydrocholesterol Reductase Inhibitors

We prepared a number of <i>N</i>-phenethyltetrahydroisoquinolines structurally related to protoberberines. They were tested for activity against bacteria, fungi, and human leukemia HL-60 cells and also for inhibition of biosynthesis: ergosterol in yeasts and cholesterol in human cells. In the latter assay panel, several of the compounds were distinguished by a strong and selective inhibition of 7-dehydrocholesterol reductase (7-DHCR, EC 1.3.1.21), an enzyme responsible for the conversion of 7-dehydrocholesterol to cholesterol in the last step of cholesterol biosynthesis. In a whole-cell assay, the most active compound <b>5f</b> showed a much stronger inhibition of overall cholesterol biosynthesis (IC₅₀ 2.3 nM) than BM 15.766 (IC₅₀ 500 nM), presently the most selective known inhibitor of 7-DHCR. Since a defect of 7-dehydrocholesterol reductase is associated with Smith–Lemli–Opitz syndrome (SLOS), the potent and selective inhibitors reported here will enable more detailed investigation of the pathogenesis of SLOS

Design, synthesis and structure-activity relationship study of wollamide B; a new potential anti TB agent

<div><p>Wollamide B is a cationic antimycobacterial cyclohexapeptide that exhibits activity against <i>Mycobacterium bovis (M</i>. <i>bovis)</i> (IC₅₀ of 3.1 μM). Aiming to define its structural activity relationship (SAR), optimizing potency and pharmacokinetic properties, libraries of analogues were synthesized following a standard Fmoc-based solid phase peptide synthesis approach. The antimycobacterial activities of wollamide B and all the synthesized analogues were tested against <i>Mycobacterium tuberculosis</i> (<i>Mtb</i>) H37Rv. Parallely, <i>in vitro</i> drug metabolism and pharmacokinetic (ADME) profiling was done for the synthesized compounds to evaluate their drug likeness. Among the 25 synthesized wollamides five of them showed potent activities with MICs ≤ 3.1 μM and found to be nontoxic against human HepG2 cells up to 100 μM. The results of the <i>in vitro</i> ADME profiling revealed the remarkable plasma stability and very good aqueous solubility of the class in general while the metabolic stability was found to be moderate to low. Of particular note, compounds <b>7c</b> (MIC = 1.1 μM) and <b>13c</b> (0.6 μM) that exhibited good balance of antimycobacterial activity vs. optimal pharmacokinetic properties could be used as a new lead for further development.</p></div

Scheme that shows the synthetic approach to wollamide B.

<p>Scheme that shows the synthetic approach to wollamide B.</p

A synthetic scheme that shows the approach used to synthesize the linear precursor of wollamide B using SPPS.

<p>Reagents and conditions: a) Fmoc-L-Leu-OH, DIPEA, DCM, 2 h; b) 20% piperidine/DMF, 10 min (2X); c) Fmoc-L-Trp (Boc)-OH, HATU, DIPEA, NMP, 1 h; d) Fmoc-D-Orn (Boc)-OH, HATU, DIPEA, NMP, 1 h; e) Fmoc-L-Asn (Trt)-OH, HATU, DIPEA, NMP, 1 h; f) Fmoc-L-Val-OH, HATU, DIPEA, NMP, 1 h; g) Fmoc-D-Leu-OH, HATU, DIPEA, NMP, 1 h; h) 20% HFIP/DC, 1 h.</p

<i>In vitro</i> antimycobacterial MICs and cytotoxicities of wollamide B analogues.

<p><i>In vitro</i> antimycobacterial MICs and cytotoxicities of wollamide B analogues.</p

Structures of the synthesized wollamide B analogues.

<p>Structures of the synthesized wollamide B analogues.</p

Structure of wollamide B.

<p>Structure of wollamide B.</p

<i>In vitro</i> plasma stabilities for selected wollamides B analogues.

<p><i>In vitro</i> plasma stabilities for selected wollamides B analogues.</p

Microsomal stabilities of wollamide B analogues.

<p>Microsomal stabilities of wollamide B analogues.</p

Antimycobacterial activities and <i>in vitro</i> ADME profiles of wollamide B (1c).

<p>Antimycobacterial activities and <i>in vitro</i> ADME profiles of wollamide B (1c).</p