One-Step versus Two-Step Synthesis of Hydrophobically Modified Ethoxylated Urethanes: Benefits and Limitations

Associative thickeners, such as hydrophobically modified ethoxylated urethanes (HEURs), are an important class of rheological modifiers allowing precise control and optimization of the rheology of waterborne coatings. In this work, we present a novel, comprehensive investigation of one-step and two-step HEUR synthesis processes, highlighting their impact on the final HEUR properties. In the conventional one-step process (current industrial practice), there are inherent limitations in producing high molecular weight polymers due to the complex competition between end-capping and polymerization. We show that the two-step method allows for much higher molecular weight polymers than the one-step method while using less amounts of toxic diisocyanates. Additionally, using the two-step method, the polymerization can be simply and efficiently controlled by the addition timepoint of the end-capping agent, which can be tailored to provide HEURs with a wide range of molecular weight and polydispersity index. However, the efficient end-capping of high molecular weight polymers remains a challenge when using conventional mixing equipment in batch reactors due to mass transfer and mixing limitations associated with the significant increase in the bulk viscosity of the reaction mixture. To overcome these limitations, alternative and more efficient mixing technologies, such as reactive extruders, should be considered for the efficient end-capping of high molecular weight polymers

Screening work flow.

<p>The different steps, the most relevant assay conditions and the go/no-go criteria of the screening campaign are indicated in boxes. The figures on the right refer to the number of compounds screened and that subsequently advanced during the campaign. From 144 compounds, 22 compounds lowered assay signal ≥ 45% for at least one TryS. From these 22, 7 BDA were false positive and the remaining 15 compounds were confirmed as enzyme inhibitors. Two of them are <b>AI</b> with potency in the submicromolar range against <i>Li</i>TryS. AI (P), 4,5-dihydroazepino[4,5-<i>b</i>]indol-2(1<i>H</i>,3<i>H</i>,6<i>H</i>)-one derivatives (P, paullone); APPDA, 6-arylpyrido[2,3-<i>d</i>]pyrimidine-2,7-diamine derivatives; BZ, benzofuroxan derivatives; BDA, <i>N</i>,<i>N'</i>-bis(3,4-substituted-benzyl) diamine derivatives.</p

Biological activity of compounds against infective <i>Trypanosoma brucei brucei</i> with downregulated expression of trypanothione synthetase (TryS).

<p><b>A)</b> Western blot analysis of cell extracts from 2x10⁷ <i>T</i>. <i>b</i>. <i>brucei</i> from the wildtype (WT), 48 h tetracycline-induced (+) and non-induced (-) TryS-RNAi cell line. Two hundred ng of recombinant <i>Tb</i>TryS was loaded as control. Bands from the molecular weight marker are indicated on left. The picture at the bottom shows the abundance of TryS for each condition as estimated by densitometry and expressed relative to the level of the WT cell line. <b>B)</b> Ponceau staining of the Western blot membrane that served as normalization control of protein load for each condition. <b>C)</b> Cytotoxicity (%) ± S.D. (n = 2) for tetracycline-induced (+) and non-induced (-) TryS-RNAi <i>T</i>. <i>b</i>. <i>brucei</i> treated with 5 μM nifurtimox or 100 nM EAP1-47.</p

Inhibitors of tritryp trypanothione synthetase (TryS) identified in this work and their biological activity.

<p>Inhibitors of tritryp trypanothione synthetase (TryS) identified in this work and their biological activity.</p

Structure of compounds affecting tritryp trypanothione synthetase activity.

<p><b>AI (P)</b>, 4,5-dihydroazepino[4,5-<i>b</i>]indol-2(1<i>H</i>,3<i>H</i>,6<i>H</i>)-one derivatives, paullones derivatives, (FS-554 and MOL2008), five APPDA, 6-arylpyrido[2,3-<i>d</i>]pyrimidine-2,7-diamine derivatives (ZEA10, ZEA35, ZEA40, ZEA41 and ZVR159), eight BDA, <i>N</i>,<i>N'</i>-bis(3,4-substituted-benzyl) diamine derivatives (EAP1-47, EAP1-63, APC1-67, APC1-87, APC1-89, APC1-99, APC1-101 and APC1-111), seven BBHPP, 1-(benzo[<i>d</i>]thiazol-2-yl)-4-benzoyl-3-hydroxy-5-phenyl-1<i>H</i>-pyrrol-2(5<i>H</i>)-one derivatives (AD81, AD84, ADMRC158, ADKPN160, ADKPN161, ADKPN164 and ADKPN165), three BZ, benzofuroxan derivatives (J18, J20 and J31) and one PD, 1<i>H</i>-purine-2,6(3<i>H</i>,7<i>H</i>)-dione derivatives [(<i>Z</i>)-8-(2-(2,4-dihydroxybenzylidene)hydrazinyl)-7-(2-hydroxy-3-phenoxy propyl)-1,3-dimethyl-1<i>H</i>-purine-2,6(3<i>H</i>,7<i>H</i>)-dione, TC227]. iPr, tBu, OBn, Mo and Ph, correspond to an isopropyl, tert-butyl, O-benzyl, 4 -morpholinyl and phenyl substitution, respectively.</p

Trypanothione dependent redox metabolism.

<p>The chemical structure of trypanothione (<i>N</i>¹,<i>N</i>⁸-bis(glutathionyl)spermidine; T(SH)₂) is depicted at the center. Synthesis: trypanothione synthetase catalyzes the ligation of two molecules of gluthatione to one of spermidine using the energy provided by two ATP molecules. Regeneration: trypanothione reductase maintains trypanothione in the reduced state at expenses of NADPH, which can be supplied by the oxidative phase of the pentose phosphate pathway <i>via</i> glucose 6-phosphate dehydrogenase. Utilization: reduced trypanothione is involved in multiple functions such as the detoxification of xenobiotics, cell proliferation, defense against oxidants and protein thiol-redox homeostasis. The multipurpose oxidoreductase tryparedoxin plays an important role catalyzing electron transfer from T(SH)₂ to different molecular targets (e.g. peroxidases, ribonucleotide reductase and protein disulfides). G6P: glucose-6-phosphate, 6PGL: 6-phosphogluconolactone, T(SH)₂: reduced trypanothione, TS_2[ox]: oxidized trypanothione, NDPs: nucleosides diphosphate, dNDP: deoxinucleosides diphosphate, E^-: electrophilic species, TS-E: trypanothione-electrophile adduct, ROOH: hydroperoxide, ONOOH: peroxynitrite, NO₂^-: nitrite.</p