Synthesis of Mimics of Pramanicin from Pyroglutamic Acid and Their Antibacterial Activity

Epoxypyrrolidinones are available by epoxidation of carboxamide-activated bicyclic lactam substrates derived from pyroglutamate using aqueous hydrogen peroxide and tertiary amine catalysis. In the case of an activating Weinreb carboxamide, further chemoselective elaboration leads to the efficient formation of libraries of epoxyketones. Deprotection may be achieved under acidic conditions to give epoxypyroglutaminols, although the ease of this process can be ameliorated by the presence of internal hydrogen bonding. Bioassay against <i>S. aureus</i> and <i>E. coli</i> indicated that some compounds exhibit antibacterial activity. These libraries may be considered to be structural mimics of the natural products pramanicin and epolactaene. More generally, this outcome suggests that interrogation of bioactive natural products is likely to permit the identification of “privileged” structural scaffolds, providing frameworks suitable for optimization in a short series of chemical steps that may accelerate the discovery of new antibiotic chemotypes. Further optimization of such systems may permit the rapid identification of novel systems suitable for antibacterial drug development

Synthesis of Neplanocin A and Its 3′-Epimer via an Intramolecular Baylis–Hillman Reaction

The key cyclopentenyl intermediate <b>11b</b> was synthesized in 4 steps from d-ribose in 41% overall yield via an efficient intramolecular Baylis–Hillman reaction. This novel key intermediate can be modified easily and transformed to neplanocin A (<b>1a</b>) and its 3′-epimer (<b>1b</b>)

Trisubstituted Thieno[3,2‑<i>b</i>]pyrrole 5‑Carboxamides as Potent Inhibitors of Alphaviruses

Chikungunya virus (CHIKV) is a re-emerging vector-borne alphavirus and is transmitted to humans by <i>Aedes</i> mosquitoes. Despite the re-emergence of CHIKV as an epidemic threat, there is no approved effective antiviral treatment currently available for CHIKV. Herein, we report the synthesis and structure–activity relationship studies of a class of thieno­[3,2-<i>b</i>]­pyrroles and the discovery of a trisubstituted thieno­[3,2-<i>b</i>]­pyrrole 5-carboxamide <b>15c</b> that exhibits potent inhibitory activity against <i>in vitro</i> CHIKV infection. Compound <b>15c</b> displayed low micromolar activity (EC₅₀ value of ca. 2 μM) and limited cytotoxic liability (CC50 > 100 μM) therefore furnishing a selectivity index of greater than 32. Notably, <b>15c</b> not only controlled viral RNA production, but efficiently inhibited the expression of CHIKV nsP1, nsP3, capsid, and E2 proteins at a concentration as low as 2.5 μM. More importantly, <b>15c</b> also demonstrated broad spectrum antiviral activity against other clinically important alphaviruses such as O’nyong–nyong virus and Sindbis virus

Copper-Catalyzed Oxidative Amidation of Aldehydes with Amine Salts: Synthesis of Primary, Secondary, and Tertiary Amides

A practical method for the amidation of aldehydes with economic ammonium chloride or amine hydrochloride salts has been developed for the synthesis of a wide variety of amides by using inexpensive copper sulfate or copper­(I) oxide as a catalyst and aqueous <i>tert</i>-butyl hydroperoxide as an oxidant. This amidation reaction is operationally straightforward and provides primary, secondary, and tertiary amides in good to excellent yields for most cases utilizing inexpensive and readily available reagents under mild conditions. In situ formation of amine salts from free amines extends the substrate scope of the reaction. Chiral amides are also synthesized from their corresponding chiral amines without detectable racemization. The practicality of this amide formation reaction has been demonstrated in an efficient synthesis of the antiarrhythmic drug <i>N</i>-acetylprocainamide

Structural Optimizations of Thieno[3,2‑<i>b</i>]pyrrole Derivatives for the Development of Metabolically Stable Inhibitors of Chikungunya Virus

Chikungunya virus (CHIKV) is a re-emerging vector-borne alphavirus, and there is no approved effective antiviral treatment currently available for CHIKV. We previously reported the discovery of thieno­[3,2-<i>b</i>]­pyrrole <b>1b</b> that displayed good antiviral activity against CHIKV infection in vitro. However, it has a short half-life in the presence of human liver microsomes (HLMs) (<i>T</i>_1/2 = 2.91 min). Herein, we report further optimization studies in which potential metabolically labile sites on compound <b>1b</b> were removed or modified, resulting in the identification of thieno­[3,2-<i>b</i>]­pyrrole <b>20</b> and pyrrolo­[2,3-<i>d</i>]­thiazole <b>23c</b> possessing up to 17-fold increase in metabolic half-lives in HLMs and good in vivo pharmacokinetic properties. Compound <b>20</b> not only attenuated viral RNA production and displayed broad-spectrum antiviral activity against other alphaviruses and CHIKV isolates but also exhibited limited cytotoxic liability (CC₅₀ > 100 μM). These studies have identified two compounds that have the potential for further development as antiviral drugs against CHIKV infection

Structural Optimizations of Thieno[3,2‑<i>b</i>]pyrrole Derivatives for the Development of Metabolically Stable Inhibitors of Chikungunya Virus

Chikungunya virus (CHIKV) is a re-emerging vector-borne alphavirus, and there is no approved effective antiviral treatment currently available for CHIKV. We previously reported the discovery of thieno­[3,2-<i>b</i>]­pyrrole <b>1b</b> that displayed good antiviral activity against CHIKV infection in vitro. However, it has a short half-life in the presence of human liver microsomes (HLMs) (<i>T</i>_1/2 = 2.91 min). Herein, we report further optimization studies in which potential metabolically labile sites on compound <b>1b</b> were removed or modified, resulting in the identification of thieno­[3,2-<i>b</i>]­pyrrole <b>20</b> and pyrrolo­[2,3-<i>d</i>]­thiazole <b>23c</b> possessing up to 17-fold increase in metabolic half-lives in HLMs and good in vivo pharmacokinetic properties. Compound <b>20</b> not only attenuated viral RNA production and displayed broad-spectrum antiviral activity against other alphaviruses and CHIKV isolates but also exhibited limited cytotoxic liability (CC₅₀ > 100 μM). These studies have identified two compounds that have the potential for further development as antiviral drugs against CHIKV infection

Effects of D9 on histone methylation and transcriptome in AML.

<p>Western blot analysis showing the level of cleaved PARP, EZh2 and a series of histone lysine methylation marks in MOLM-14 (a) and KG-1a cells (b) treated by D9 at indicated concentrations for 48 and 72 hours. (c) Heat map of differential genesets between sensitive and resistant cell lines with D9 treatment. Three sensitive (MOLM-14, MV4-11 and TF-1) and three resistant cell lines (Mono-Mac-1, KG-1a and THP-1) were treated with D9 at 1 or 5 μM for 48 hours. Total RNA was isolated for microarray and SAM analysis. 327 genes were up-regulated and 220 genes were down-regulated upon D9 treatment in sensitive cells relative to resistant cells using 10% false discovery rate (FDR) cut-off. (d) Ingenuity Pathway Analysis (IPA) of differentially up-regulated geneset and down-regulated geneset (dii) showing their strong connections to PI3K/AKT and MEK/ERK signaling pathways.</p

EC50 profile of D9 in human cancer cell lines.

<p>(a) Chemical structure of D9. (b) Bar graphs showing EC50 of D9 measured in a panel of solid (bi) and blood (bii) cancer cell lines using cell viability assay.1 x 10^³ cells of individual cell lines were seeded into 96-well plates in triplicates and D9 at 10 different doses was added 24 hours post cell seeding. Proliferation was measured after 96 hours treatment of D9 using an ATP based cell viability assay. EC50 of D9 was calculated by nonlinear regression (curve fit) using GraphPad PRISM3. Data represent the means of EC50 of D9 measured in three independent experiments, with each experiment run in triplicates.</p

Effects of D9 on AKT and ERK phosphorylation in AML.

<p>(a)Western blot analysis of p-ERK (T202/204), total ERK, p-AKT (S473), total AKT and ACTIN in indicated AML cell lines treated with D9 for 24 hours and 48 hours. (b) Western blot analysis showing the effects of D9 on Bim and Survivin in AML cell lines as in (a). (c) The frozen primary AML patient blasts were recovered for 24 hours and the dead cells were removed using Dead Cell Removal Kit just before D9 treatment. The blasts were treated for 96 hours for cell viability assay and 48 hours for western blot analysis. The diagrams showed the drug response curves of AML patient blasts towards D9 (ci), measurement of EC50 of D9 using cell viability assay (cii) and western blot analysis of PARP, p-ERK (T202/204), total ERK, p-AKT (S473), total AKT and ACTIN in AML patient blasts as well as MOLM-14 with and without D9 treatment (ciii). Each data point in the plots of drug response curves of D9 represents the mean ± SEM of six replicates at each specified concentration of D9, N = 3.</p

Effective anti-leukemia stem cells (LSC) activity of D9 in AML.

<p>(a) Bar graphs showing FACS analysis of the proportion of CD34+CD38- population in TF-1a after the single treatment with D9, SAHA or DAC for 72 hours. (b) Representative FACS histogram profiles of CD34+CD38- cell population in TF-1a cells treated with D9 (100 nM) alone or in combination with either Ara-C (20 nM) or ADR (50 nM). (c) Bar graphs showing the proportion of CD34+CD38- population in TF-1a cells treated as in B. (d) Bar graphs showing the proportion of CD34+CD38- population in TF-1a treated with D9 (20 nM) with or without Ara-C (20 nM) for 14 days. (e). Bar graphs showing the percentage of CD34+CD38- cell population in TF-1a cells treated as indicated. (f) Colony Formation Unit (CFU) assay showing the effects of D9, SAHA or DAC on basal or Ara-C or ADR-induced colony formation capacity of TF-1a cells. The medium and drugs were replenished every 3 to 4 days and the dead cells were removed by Dead Cell Removal Kit. 1 x 10^3 live cells were seeded with semi-solid colony formation medium and incubated for 2 weeks before enumeration. Representative images of the colony formation of TF-1a were shown on (fi) and bar graphs were shown the colony numbers on (fii). Data are mean ± SEM; N = 3; *P < 0.05, **P < 0.01, ***P < 0.001, ns represents no significance, unpaired two tailed t test.</p