New drugs and molecular targets are urgently needed to address the emergence and spread of drug-resistant tuberculosis. Mycobacterium tuberculosis ( Mtb) inosine 5'-monophosphate dehydrogenase 2 ( MtbIMPDH2) is a promising yet controversial potential target. The inhibition of MtbIMPDH2 blocks the biosynthesis of guanine nucleotides, but high concentrations of guanine can potentially rescue the bacteria. Herein we describe an expansion of the structure-activity relationship (SAR) for the benzoxazole series of MtbIMPDH2 inhibitors and demonstrate that minimum inhibitory concentrations (MIC) of ≤1 μM can be achieved. The antibacterial activity of the most promising compound, 17b (Q151), is derived from the inhibition of MtbIMPDH2 as demonstrated by conditional knockdown and resistant strains. Importantly, guanine does not change the MIC of 17b, alleviating the concern that guanine salvage can protect Mtb in vivo. These findings suggest that MtbIMPDH2 is a vulnerable target for tuberculosis.
Ferrocenyl-Alkyl-Protected
Sugar (Fc-Sug) and Ferrocenyl-Oxo-Alkyl-Protected
Sugar (Fc-Oxo-Sug) were deposited on the basal plane of Highly Oriented
Pyrolytic Graphite (HOPG) using a drop-casting method. Ultrathin films
of these molecules were investigated using Atomic Force Microscopy
to understand the growth at low coverage. Both molecules are forming
highly ordered one-dimensional molecular islands, which are growing
from a dimer building block. The dimer and interdimer interactions
(along the length of islands) are stabilized by −C2O···H–C hydrogen bonding. Unlike for Fc-Sug,
the islands of Fc-Oxo-Sug are extended to tens of micrometers, and
the growth is only limited by terrace edges or other islands on the
surface. This exceptional growth of islands is understood in terms
of an additional −CO···H–C–
hydrogen bonding leading to stronger interdimer interactions along
the length of the islands compared to Fc-Sug.
Herpes simplex virus 1 (HSV-1) has infected more than 80% of the population. Reactivation of the virus causes diseases ranging in severity from benign cold sores to fatal encephalitis. Current treatments involve viral DNA replication inhibitors, but the emergence of drug-resistant mutants is observed frequently, highlighting the need for novel antiviral therapies. Infected cell protein 0 (ICP0) of HSV-1 is encoded by an immediate early gene and plays a fundamental role during infection, because it enables viral gene expression and blocks antiviral responses. One mechanism by which ICP0 functions is through an E3 ubiquitin ligase activity that induces the degradation of targeted proteins. A ΔICP0 virus or mutants with deficiencies in E3 ligase activity cannot counteract beta interferon (IFN-β)-induced restriction of viral infection, are highly immunogenic, are avirulent, and fail to spread. Thus, small molecules interfering with essential and conserved ICP0 functions are expected to compromise HSV-1 infection. We have developed a high-throughput screening assay, based on the autoubiquitination properties of ICP0, to identify small-molecule inhibitors of ICP0 E3 ubiquitin ligase activity. Through a pilot screening procedure, we identified nine compounds that displayed dose-dependent inhibitory effects on ICP0 but not on Mdm2, a control E3 ubiquitin ligase. Following validation, one compound displayed ICP0-dependent inhibition of HSV-1 infection. This compound appeared to bind ICP0 in a cellular thermal shift assay, it blocked ICP0 self-elimination, and it blocked wild-type but not ICP0-null virus gene expression. This scaffold displays specificity and could be used to develop optimized ICP0 E3 ligase inhibitors.
IMPORTANCE Since acyclovir and its derivatives were launched for herpesviruses control almost four decades ago, the search for novel antivirals has waned. However, as human life expectancy has increased, so has the number of immunocompromised individuals who receive prolonged treatment for HSV recurrences. This has led to an increase in unresponsive patients due to acquired viral drug resistance. Thus, novel treatments need to be explored. Here we explored the HSV-1 ICP0 E3 ligase as a potential antiviral target because (i) ICP0 is expressed before virus replication, (ii) it is essential for infection in vivo, (iii) it is required for efficient reactivation of the virus from latency, (iv) inhibition of its E3 ligase activity would sustain host immune responses, and (v) it is shared by other herpesviruses. We report a compound that inhibits HSV-1 infection in an ICP0-dependent manner by inhibiting ICP0 E3 ligase activity.
γ‐Oxo α‐amino acids and γ‐aryl α‐amino acids are compounds with very interesting biological properties and are active components of many drug molecules. Oxo amino acids are also used as synthetic precursors for a number of unnatural amino acids and amino alcohols. We report a very efficient synthesis of such compounds through the coupling of aromatic dithianes, prepared from aromatic aldehydes and an iodide derivative of serine. The dithiane groups in compounds thus obtained can be either hydrolyzed or reduced to generate 4‐oxo‐4‐aryl or 4‐aryl 2‐amino butanol derivatives, respectively, which, on further transformations, can be converted into the title compounds. Starting with L‐serine provides the corresponding D‐amino acids with complete enantiopurity. The reported method is economically viable and complements the existing methods, which rely largely on cross‐coupling reactions.
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