3 research outputs found
Lipase-Catalyzed Aza-Michael Reaction on Acrylate Derivatives
A methodology has been developed
for an efficient and selective
lipase-catalyzed aza-Michael reaction of various amines (primary and
secondary) with a series of acrylates and alkylacrylates. Reaction
parameters were tuned, and under the optimal conditions it was found
that <i>Pseudomonas stutzeri</i> lipase and <i>Chromobacterium
viscosum</i> lipase showed the highest selectivity for the aza-Michael
addition to substituted alkyl acrylates. For the first time also,
some CLEAs were examined that showed a comparable or higher selectivity
and yield than the free enzymes and other formulations
Identification of the First Highly Subtype-Selective Inhibitor of Human GABA Transporter GAT3
Screening a library of small-molecule
compounds using a cell line
expressing human GABA transporter 3 (hGAT3) in a [<sup>3</sup>H]GABA
uptake assay identified isatin derivatives as a new class of hGAT3
inhibitors. A subsequent structure–activity relationship (SAR)
study led to the identification of hGAT3-selective inhibitors (i.e.,
compounds <b>20</b> and <b>34</b>) that were superior
to the reference hGAT3 inhibitor, (<i>S</i>)-SNAP-5114,
in terms of potency (low micromolar IC<sub>50</sub> values) and selectivity
(>30-fold selective for hGAT3 over hGAT1/hGAT2/hBGT1). Further
pharmacological
characterization of compound <b>20</b> (5-(thiophen-2-yl)indoline-2,3-dione)
revealed a noncompetitive mode of inhibition at hGAT3. This suggests
that this compound class, which has no structural resemblance to GABA,
has a binding site different from the substrate, GABA. This was supported
by a molecular modeling study that suggested a unique binding site
that matched the observed selectivity, inhibition kinetics, and SAR
of the compound series. These compounds are the most potent GAT3 inhibitors
reported to date that provide selectivity for GAT3 over other GABA
transporter subtypes
Targeting a Subpocket in <i>Trypanosoma brucei</i> Phosphodiesterase B1 (TbrPDEB1) Enables the Structure-Based Discovery of Selective Inhibitors with Trypanocidal Activity
Several trypanosomatid
cyclic nucleotide phosphodiesterases (PDEs)
possess a unique, parasite-specific cavity near the ligand-binding
region that is referred to as the P-pocket. One of these enzymes, <i>Trypanosoma brucei</i> PDE B1 (TbrPDEB1), is considered a drug
target for the treatment of African sleeping sickness. Here, we elucidate
the molecular determinants of inhibitor binding and reveal that the
P-pocket is amenable to directed design. By iterative cycles of design,
synthesis, and pharmacological evaluation and by elucidating the structures
of inhibitor-bound TbrPDEB1, hPDE4B, and hPDE4D complexes, we have
developed 4a,5,8,8a-tetrahydrophthalazinones as the first selective
TbrPDEB1 inhibitor series. Two of these, <b>8</b> (NPD-008)
and <b>9</b> (NPD-039), were potent (<i>K</i><sub>i</sub> = 100 nM) TbrPDEB1 inhibitors with antitrypanosomal effects
(IC<sub>50</sub> = 5.5 and 6.7 μM, respectively). Treatment
of parasites with <b>8</b> caused an increase in intracellular
cyclic adenosine monophosphate (cAMP) levels and severe disruption
of <i>T. brucei</i> cellular organization, chemically validating
trypanosomal PDEs as therapeutic targets in trypanosomiasis