23 research outputs found
Employing Modular Polyketide Synthase Ketoreductases as Biocatalysts in the Preparative Chemoenzymatic Syntheses of Diketide Chiral Building Blocks
SummaryChiral building blocks are valuable intermediates in the syntheses of natural products and pharmaceuticals. A scalable chemoenzymatic route to chiral diketides has been developed that includes the general synthesis of α-substituted, β-ketoacyl N-acetylcysteamine thioesters followed by a biocatalytic cycle in which a glucose-fueled NADPH-regeneration system drives reductions catalyzed by isolated modular polyketide synthase (PKS) ketoreductases (KRs). To identify KRs that operate as active, stereospecific biocatalysts, 11 isolated KRs were incubated with 5 diketides and their products were analyzed by chiral chromatography. KRs that naturally reduce small polyketide intermediates were the most active and stereospecific toward the panel of diketides. Several biocatalytic reactions were scaled up to yield more than 100 mg of product. These syntheses demonstrate the ability of PKS enzymes to economically and greenly generate diverse chiral building blocks on a preparative scale
Effects of Eupalinilide E and UM171, Alone and in Combination on Cytokine Stimulated Ex-Vivo Expansion of Human Cord Blood Hematopoietic Stem Cells
Eupalinilide E was assessed for ex-vivo expansion activity on hematopoietic stem cells (HSCs) from human cord blood (CB) CD34+ cells in serum-free, SCF, TPO and FL stimulated 7 day cultures. Eupalinilide E ex-vivo enhanced phenotyped (p) HSCs and glycolysis of CD34+ cells isolated 7 days after culture as measured by extracellular acidification rate, but did not alone show enhanced NSG engrafting capability of HSCs as determined by chimerism and numbers of SCID Repopulating cells, a quantitative measure of functional human HSCs. This is another example of pHSCs not necessarily recapitulating functional activity of these cells. Lack of effect on engrafting HSCs may be due to a number of possibilities, including down regulation of CXCR4 or of the homing capacity of these treated cells. However, Eupalinilide did act in an additive to synergistic fashion with UM171 to enhance ex vivo expansion of both pHSCs, and functionally engrafting HSCs. While reasons for the disconnect between pHSC and function of HSCs with Eupalinilide E alone cultured CB CD34+ cells is yet to be determined, the data suggest possible future use of Eupalinilide and UM171 together to enhance ex vivo production of CB HSCs for clinical hematopoietic cell transplantation
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Pan-active imidazolopiperazine antimalarials target the Plasmodium falciparum intracellular secretory pathway.
A promising new compound class for treating human malaria is the imidazolopiperazines (IZP) class. IZP compounds KAF156 (Ganaplacide) and GNF179 are effective against Plasmodium symptomatic asexual blood-stage infections, and are able to prevent transmission and block infection in animal models. But despite the identification of resistance mechanisms in P. falciparum, the mode of action of IZPs remains unknown. To investigate, we here combine in vitro evolution and genome analysis in Saccharomyces cerevisiae with molecular, metabolomic, and chemogenomic methods in P. falciparum. Our findings reveal that IZP-resistant S. cerevisiae clones carry mutations in genes involved in Endoplasmic Reticulum (ER)-based lipid homeostasis and autophagy. In Plasmodium, IZPs inhibit protein trafficking, block the establishment of new permeation pathways, and cause ER expansion. Our data highlight a mechanism for blocking parasite development that is distinct from those of standard compounds used to treat malaria, and demonstrate the potential of IZPs for studying ER-dependent protein processing
A Protocol To Generate Phthaloyl Peroxide in Flow for the Hydroxylation of Arenes
A flow protocol for
the generation of phthaloyl peroxide has been
developed. This process directly yields phthaloyl peroxide in high
purity (>95%) and can be used to bypass the need to isolate and
recrystallize
phthaloyl peroxide, improving upon earlier batch procedures. The flow
protocol for the formation of phthaloyl peroxide can be combined with
arene hydroxylation reactions and provides a method for the consumption
of peroxide as it is generated to minimize the accumulation of large
quantities of peroxide
Dearomatization Reactions Using Phthaloyl Peroxide
A new
oxidative dearomatization reaction has been developed using
phthaloyl peroxide to chemoselectively install two oxygen–carbon
bonds into aromatic precursors. The oxidation reaction proceeds only
once; addition of superstoichiometric equivalents of phthaloyl peroxide
does not react further with the newly generated 1,3-cyclohexadiene.
The reaction has been challenged by the addition of different functional
groups and shown to maintain chemoselectivity. Due to the broad reactivity
with 1,2-methylenedioxybenzene derivatives, linear free energy correlations
were determined and support a mechanism proceeding through diradicals
analogous to arene-hydroxylation reactions using phthaloyl peroxide
Synthesis of Eupalinilide E, a Promoter of Human Hematopoietic Stem and Progenitor Cell Expansion
Improving the ex
vivo and in vivo production of hematopoietic stem
and progenitor cells (HSPCs) has the potential to address the short
supply of these cells that are used in the treatment of various blood
diseases and disorders. Eupalinilide E promotes the expansion of human
HSPCs and inhibits subsequent differentiation, leading to increased
numbers of clinically useful cells. This natural product represents
an important tool to uncover new methods to drive expansion while
inhibiting differentiation. However, in the process of examining these
effects, which occur through a novel mechanism, the natural product
was consumed, which limited additional investigation. To provide renewed
and improved access to eupalinilide E, a laboratory synthesis has
been developed and is reported herein. The synthetic route can access
>400 mg in a single batch, employing reactions conducted on useful
scales in a single vessel. Key transformations enabling the approach
include a diastereoselective borylative enyne cyclization and a late-stage
double allylic C–H oxidation as well as adapted Luche reduction
and aluminum-mediated epoxidation reactions to maximize the synthetic
efficiency. Retesting of the synthetic eupalinilide E confirmed the
compound’s ability to expand HSPCs and inhibit differentiation