Tert-butyldiphenylsilyl Group Research Articles

Synthesis and characterization of a julolidine-based electro-optic molecular glass.

Organic electro-optic (EO) materials have recently gained considerable attention owing to their advantages compared to inorganic EO materials. Among different kinds of organic EO materials, organic EO molecular glass exhibits desired prospect because of its high chromophore loading density and large macroscopic EO activity. The objective of this study is to design and synthesize a novel organic EO molecular glass JMG utilizing julolidine moiety as the electron donor, thiophene moiety as the conjugated bridge, trifluoromethyl substituted tricyanofuran derivate (Ph-CF3-TCF) as the electron acceptor. The JMG's structure was characterized through NMR and HRMS. The photophysical property, glass transition temperature, first hyperpolarizability (β) and dipole moment (μ) of JMG were determined through UV-vis spectra, DSC test and DFT calculation. JMG's Tg reached to 79 °C and it can form high-quality optical film. The theoretical calculation shows that the first hyperpolarizability (β) and dipole moment (μ) of JMG were calculated to 730×10-30 esu and 21.898 D. After connecting poling with the poling voltage of 49 V/μm at 90 ℃for 10 min, the highest EO coefficient (r33) of the poled JMG films reached to 147 pm/V. A novel julolidine-based NLO chromophore with two tert-butyldiphenylsilyl (TBDPS) groups was successfully prepared and characterized. TBDPS group is introduced as the film-forming group, and it also plays the role of isolation group, which can suppress the electrostatic interaction between chromophores, improve the poling efficiency and further enhance the EO activity. The excellent performances endow JMG with potential applications in device fabrication.

Mild method for the synthesis of α-glycosyl chlorides: A convenient protocol for quick one-pot glycosylation

A simple and efficient protocol for the preparation of α-glycosyl chlorides within 15–30 min is described which employs a stable, cheap, and commercially available Trichloroisocyanuric acid (TCCA) as non-toxic chlorinating agent along with PPh3. This process involved a wide range of substrate scope and is well-suited with labile hydroxyl protecting groups such as benzyl, acetyl, benzoyl, isopropylidene, benzylidene, and TBDPS (tert-butyldiphenylsilyl) groups. This process is operationally simple, mild conditions and obtained good yields with excellent α selectivity. Moreover, a multi-catalyst one-pot glycosylation can be carried out to transform the glycosyl hemiacetals directly to a various O-glycosides in high overall yields without the need for separation or purification of the α-glycosyl chloride donors.

Investigation of cytotoxic properties of some isoindole-related compounds bearing silyl and azide groups with in vitro and in silico studies

This study aims to evaluate the synthesis of isoindole-1,3-dione analogues and their cytotoxic potential. A549 and HeLa cells exposed to 250–100–50–25 µM doses of each derivative were incubated for 24, 48, and 72 h. The cytotoxicity of the isoindole-1,3-dione derivatives was analyzed using the cell growth inhibition assay and the cell membrane damage test. (3aR,5R,6R,7aS)-5-Azido-2-benzyl-6-hydroxyhexahydro-1H-isoindole-1,3(2H)-dione (1d), (3aR,5R,6R,7aS)-5-azido-6-((tert-butyldiphenylsilyl)oxy)-2-ethylhexahydro-1H-isoindole-1,3(2H)-dione (2a), and (3aR,5R,6R,7aS)-5-azido-6-((tert-butyldiphenylsilyl)oxy)-2-methylhexahydro-1H-isoindole-1,3(2H)-dione (2b) compounds inhibited the growth of the A549 and HeLa cells caused membrane damage and exhibited a dose-dependent cytotoxic effect on lung and cervical carcinoma cells. The effect of tert-butyldiphenylsilyl (TBDPS) groups on cytotoxicity was observed in compounds 2a and 2b, but not in the other compounds. Considering the effect of groups attached to the nitrogen atom, the best activity was exhibited in 2b molecule to which the methyl group is attached. Additionally, the interactions of compounds (3aR,5R,6R,7aS)-5-azido-6-hydroxy-2-methylhexahydro-1H-isoindole-1,3(2H)-dione (1b), 1d, 2a and 2b with mammalian rapamycin target, human ribosomal S6 kinase 1 and human epidermal growth factor receptor were investigated by molecular docking studies, . According to the docking results, 2a and 2b compounds containing a TBDPS group have stronger binding energies than 1b and 1d compounds against all target receptors.

A γ-butyrolactone-derived poly(vinyl ester) with pendant groups recyclability and controlled release of poly(vinyl alcohol): Synthesis, recyclability, and physical properties

A pendant group recyclable poly (vinyl ester) [poly vinyl 4-((tert-butyldiphenylsilyl) oxy) butanoate, PVBT] was synthesized by classic free radical polymerization of a γ-butyrolactone (γ-BL)-derived vinyl ester. With the locking by tert-butyldiphenylsilyl group on the pendant groups, the obtained PVBT is stable and available for further processing. When the locking group is removed by adding tetra-n-butylammonium fluoride, the PVBT will decompose to the widely used poly (vinyl alcohol) (PVA) with 100% recovery of γ-BL, which can be reused to synthesize the monomer. In addition, the decomposition of PVBT can be controlled by modulating the removal of the locking group, resulting in PVA with different hydroxyl substituent contents. It was found that the elongation at break of PVBT can reach 8100%, which is 30 times that of polyvinyl acetate (PVAc). Furthermore, the PVBT possesses stronger thermal stability and lower glass transition temperature than PVAc due to their longer and silicon-containing pendant groups.

Simultaneously Improving the Optical, Dielectric, and Solubility Properties of Fluorene-Based Polyimide with Silyl Ether Side Groups

Three fluorene-based polyimides with silyl ether groups (Si–PIs) were successfully synthesized by a simple and efficient silicon etherification reaction of hydroxyl-containing polyimides (OH–PIs) and tert-butylchlorodiphenylsilane (TBDPSCl), and their structures were confirmed by 1H NMR and IR spectra. The bulky nonpolar tert-butyldiphenylsilyl (TBDPS) side groups in the modified PI unit instead of the strong electron donor −OH group is conducive to decreasing electronic conjugation and charge transfer (CT) interaction along the PI chain. Accordingly, the optical, dielectric, and solubility properties of the modified Si–PI films are simultaneously improved compared with the precursor OH–PI films. The modified Si–PI films demonstrate a meaningful enhancement in the transmittances at a wavelength of 400 nm (T400) to 74–81% from 42 to 55% of OH–PI films and the regeneration of fluorescence characteristics. The dielectric constant and loss of Si–PI films are also obviously reduced to 2.63–2.75 and 0.0024–0.0091 at 1 kHz from 4.19 to 4.78 and 0.0173–0.0295 of OH–PI films, respectively, due to substituted with the bulky nonpolar TBDPS groups to increase the free volume and hydrophobicity of Si–PI films. The solubility of Si–PIs in low- or nonpolar solvents (such as CHCl3, CH2Cl2, acetone, and toluene) is significantly improved. Furthermore, Si–PI films still maintain relatively good thermal properties with the 5% weight loss temperature (T5%) in the range 470–491 °C under a nitrogen atmosphere and the glass transition temperature (Tg) in the range 245–308 °C.

Enhanced thermal stability and electro-optic activity from fluorene-based nonlinear optical chromophores

Two series of nonlinear optical chromophores G1–G4 and J1-J4 based on diethylaminophenyl or julolidinyl-based donor and tricyanovinyldihydrofuran acceptor have been synthesized. Compared to the unmodified isophorone bridge of chromophore G1 and J1, the bridges of chromophores G2/J2 and G3-G4/J3-J4 were modified with tert-butyldimethylsilyl (TBDMS) groups and fluorene group, respectively. In addition, we introduced bulky tert-butyldiphenylsilyl (TBDPS) groups to the donor of chromophore G4 and J4 to further increase poling efficiency. The results show that the chromophores G3-G4/J3-J4 modified with fluorene groups on the bridge have higher stability and larger electro-optic coefficient than chromophores G1-G2 and J1-J2. Electro-optical films doped with chromophore G1-G4 and J1-J4 have been poled to give r33 values of 69, 96, 118, 133, 143, 201, 240 and 261 pm/V at 1.31 μm, respectively. All these provide valuable insight into understanding of the impact of an isolation group on the performance of chromophores.

Synthesis and characterization of a novel monolithic electro-optic molecular glass

To explore the simple strategy for developing excellent electro-optic (EO) materials, a monolithic EO molecular glass (EOMG1) based on thiophene π-conjugation and tricyanofuran acceptor (FTC) was synthesized. A tert-butyldiphenylsilyl (TBDPS) group was introduced to the FTC-based nonlinear optic (NLO) chromophore. The glass transition temperature (Tg) of the amorphous films was near 75 ℃, confirmed EOMG1’s glassy state. The theoretical calculation shows that the first hyperpolarizability (β) and dipole moment (μ) of EOMG 1 were calculated to 584 × 10−30esu and 20.73 D. After poling, the poled films EOMG1 diplay large EO activity (r33) of 160 pm/V at 1310 nm. The r33 value is greatly enhanced compared to the reported side-chain EO polymer containing the similar FTC-type NLO chromophore due to the increased loading density of the pure chromophore films and the TBDPS group’s role of effective isolation.

An Efficient Modular One-Pot Synthesis of Heparin-Based Anticoagulant Idraparinux.

Idraparinux is a fully O-sulfated α-methyl glycoside of heparin pentasaccharide motif known to interact with the antithrombin III domain and act as anticoagulant. The current most effective synthesis of Idraparinux is complicated and nonstereoselective, requiring numerous stepwise procedures with low yields. We report here an efficient modular one-pot synthesis of Idraparinux involving the use of a glycosyl phosphate with 6- O- tert-butyl diphenyl silyl group and a d-glucuronic acid-containing disaccharide thioglycoside with 6- O-acetyl group as donor building blocks for the α-directing one-pot glycosylations with an l-iduronic acid-containing disaccharide acceptor building block. The uronic acid was incorporated in a disaccharide module used in the one-pot synthesis to avoid the complicated late-stage installation of these acidic sugars. The one-pot synthesis of Idraparinux demonstrated here is an effective strategy and should be applicable to the modular assembly of other heparan sulfates with regiodefined sulfation pattern for functional study.

Molecular Engineering of Structurally Diverse Dendrimers with Large Electro-Optic Activities.

To boost electro-optic (EO) performance, a series of multichromophore dendrimers have been developed based on higher hyperpolarizability (CLD-type) chromophore cores that have been used previously (FTC-type dendrimers). The multichromophore dendrimers were molecularly engineered to have either three arms, two arms, or one arm; long or short linkers; and a fluorinated dendron (FD) or tert-butyldiphenylsilyl (TBDPS) shell. The EO performance obtained by FDSD (poling efficiency = 1.60 nm2 V-2), based on succinic diester linkers, was higher than the analogue with longer adipic diester linkers and higher than the analogs with fewer chromophore moieties. Due to the shorter succinic diester linker and improved site isolation, the dendrimer chromophore with TBDPS groups exhibited enhanced glass-transition temperature ( Tg = 108 °C) and comparable poling efficiency (1.62 nm2 V-2) to the FD-containing version. These neat EO dendrimers have a higher index of refraction ( n = 1.75-1.84 at 1310 nm) than guest-host polymeric EO materials ( n ≈ 1.6, 1310 nm) and FTC-type EO dendrimers ( n = 1.73, 1310 nm), which is important, because a key metric for Mach-Zehnder modulators is proportional to n3. In addition, binary chromophore organic glasses (BCOGs) were prepared by doping a secondary EO chromophore at 25 wt % into neat dendrimers. Enhancements of EO performance were found in all BCOG materials compared with neat dendrimers due to the effect of blending. As a result of increased chromophore density, the n values of the BCOGs improved to 1.81-1.92. One BOCG, in particular, displayed the highest poling efficiency (2.35 nm2 V-2) and largest EO coefficient ( r33) value of 275 pm V-1 at 1310 nm, which represents a high n3 r33 figure-of-merit of 1946 pm V-1. The high poling efficiencies and n3 r33 figure-of-merit combined with excellent film forming confirm these neat dendrimers and BCOGs based on them as promising candidates for incorporation into photonic devices.

Efficient Synthesis of α‐Glycosyl Chlorides Using 2‐Chloro‐1,3‐dimethylimidazolinium Chloride: A Convenient Protocol for Quick One‐Pot Glycosylation

A mild and convenient method for the synthesis of α‐glycosyl chlorides in high 80–96 % yields within 15–30 min using 2‐chloro‐1,3‐dimethylimidazolinium chloride (DMC) is disclosed. The method has a wide substrate scope and is compatible with labile OH protecting groups, including benzyl, acetyl, benzoyl, isopropylidene, benzylidene, TBDMS (tert‐butyldimethylsilyl), and TBDPS (tert‐butyldiphenylsilyl) groups. The excellent α selectivity obtained in this reaction is attributed to in‐situ isomerization of β‐glycosyl chlorides to the more stable α‐glycosyl chlorides, as demonstrated by 1H NMR spectroscopic studies. Disarmed sugars with OBz or OAc groups at C‐2 were chlorinated at a faster rate but ismomerized (β→α) at a slower rate than armed sugars with an OBn group at C‐2. More importantly, the method enables highly desirable one‐pot glycosylation reactions to take place, thus allowing efficient syntheses of disaccharides and simple O‐glycosylated sugars in high overall yields without the need for separation or purification of the α‐glycosyl chloride donors. This method will be especially useful for direct glycosylation reactions using glycosyl chloride donors that are unstable upon separation and purification.

A novel colorimetric sensor based on BODIPY-coumarin dye for simultaneous detection of cyanide and fluoride

A novel colorimetric and fluorescent sensor 6 for fluoride and cyanide was developed based on BODIPY-coumarin platform and its anions sensing properties were investigated in the mixture of acetonitrile and Tris–HCl buffer (v/v = 95:5, pH = 7.5). Probe 6 could simultaneously detect F– and CN– through colorimetric method over the other competitive anions, such as Cl–, Br–, I–, NO3–, ClO4–, HSO4–, S2– and H2PO4–. It exhibited a distinct color change from red to green upon addition of F– through deprotection of tert-butyldiphenylsilyl group of coumarin. Moreover, it displayed an obvious color change from red to yellow through deprotection process firstly, then with a nucleophilic displacement mechanism. Therefore, the sensor 6 provides a novel method to simultaneously detect F− and CN− with different color change in the same solvent environment. The detection limit of sensor 6 toward F– and CN– ion was determined to be 0.43μM and 1.9μM respectively,

Synthesis and Atropisomerism of Cascaded Tetraphenylporphyrin–[60]Fullerene Hybrids

Flexible, linked dendritic tetraphenylporphyrin (TPP)-fullerene hybrids were synthesized. They were designed to gain insight into and mimic the primary events in the natural photosynthetic reaction center. These multiporphyrin moieties are based on a light-harvesting concept. Moreover, they incorporate multiple redox components aligned along a redox gradient. Newkome-type dendrons were added to these TPP-fullerene hybrids. In principle they can mediate pH-dependent water solubility, which, however, could not be observed in this case. A protecting-group strategy using tert-butyldiphenylsilyl groups allows convergent synthesis of the dendritic compounds. The dendritic multiporphyrins were synthesized separately and can be used as individual building blocks. Atropisomerism was observed in the dendritic compounds, and single atropisomers could be assigned to the corresponding peaks of a characteristic pattern in the NMR spectra. Deprotection of the Newkome-type dendrons was shown to be feasible under mild conditions that leave the redox gradient intact.

A PEGylated Fluorescent Turn‐On Sensor for Detecting Fluoride Ions in Totally Aqueous Media and Its Imaging in Live Cells

Owing to the considerable significance of fluoride anions for health and environmental issues, it is of great importance to develop methods that can rapidly, sensitively and selectively detect the fluoride anion in aqueous media and biological samples. Herein, we demonstrate a robust fluorescent turn-on sensor for detecting the fluoride ion in a totally aqueous solution. In this study, a biocompatible hydrophilic polymer poly(ethylene glycol) (PEG) is incorporated into the sensing system to ensure water solubility and to enhance biocompatibility. tert-Butyldiphenylsilyl (TBDPS) groups were then covalently introduced onto the fluorescein moiety, which effectively quenched the fluorescence of the sensor. Upon addition of fluoride ion, the selective fluoride-mediated cleavage of the Si-O bond leads to the recovery of the fluorescein moiety, resulting in a dramatic increase in fluorescence intensity under visible light excitation. The sensor is responsive and highly selective for the fluoride anion over other common anions; it also exhibits a very low detection limit of 19 ppb. In addition, this sensor is operative in some real samples such as running water, urine, and serum and can accurately detect fluoride ions in these samples. The cytotoxicity of the sensor was determined to be Grade I toxicity according to United States Pharmacopoeia and ISO 10993-5, suggesting the very low cytotoxicity of the sensor. Moreover, it was found that the senor could be readily internalized by both HeLa and L929 cells and the sensor could be utilized to track fluoride level changes inside the cells.

Theoretical insight into the mechanism of Pt(ІІ)-catalyzed [3+2] cycloaddition reactions of propadienyl silyl ethers with alkenyl ethers

By carrying out DFT calculations, we have performed a detailed mechanism study on the Pt(II)-catalyzed [3 + 2] cycloaddition reactions of propadienyl silyl ethers with alkenyl ethers. We calculate the mechanism proposed by Iwasawa et al. about the cycloaddition reactions of triisopropylsilyl (TIPS) 1,2-propadienyl ether (1a) with 2-methoxypropene (2a), tert-butyldiphenylsilyl (TBDPS) 1,2-propadienyl ether (1b) with 2a, and 1b with benzyl substituted alkenyl ether (2b), respectively. The calculated results show that the two reactions proceed according to similar elementary step mechanism. For the cycloaddition reaction of 1a with 2a, the products are cyclopentene derivative 3a and methylenecyclobutane derivative 4a. In contrast, for the cycloaddition reaction of 1b with 2a and 1b with 2b, due to the less electron-donating TBDPS group and the more steric repulsion between TBDPS group and the metal fragment, the predominant product is 3a.

Challenging Deprotection Steps During the Synthesis of Tetra- and Pentasaccharide Fragments of the LeaLex Tumor-Associated Hexasaccharide Antigen

We report the convergent synthesis of two novel tetrasaccharide and two novel pentasaccharide fragments of the Le(a)Le(x) TACA: the tetrasaccharides contain neither the galactose at the Le(a) nonreducing end nor the fucose at the Le(x) reducing end; the pentasaccharides only lack the galactose residue at the Le(a) nonreducing end. Two of the analogues were prepared as hexyl glycosides to be used in NMR experiments and as soluble inhibitors in binding studies and two as 6-aminohexyl glycosides to be conjugated to carrier proteins. Our strategy relied on stepwise extensions using excess monosaccharide glycosyl donors (trichloroacetimidates and thioglycosides) in sequential glycosylation reactions. The protecting groups were chosen to limit the number of deprotection steps required to obtain the final derivatives. While this strategy ensured that all glycosylation reactions proceeded in very good yields (70-84%), deprotection of the oligosaccharide intermediates was challenging. Global deprotection using Birch metal dissolving conditions did not remove the tert-butyldiphenylsilyl group, which indeed was incompatible with such reaction conditions. Attempts to remove the TBDPS with tetrabutylammonium fluoride was unsuccessful and led to a complex mixture of compounds that could not be separated. The desired hexyl and aminohexyl tetrasaccharides were finally obtained after four- and five-step deprotection sequences, respectively. Deprotection of the pentasaccharide intermediate to give the hexyl and aminohexyl analogues also led to unexpected results. Indeed, during Zemplén deacylation, a chloroacetamide chlorine atom was displaced by methoxide ions leading to the corresponding methoxyacetamide. Once the chloroacetamide was fully reduced to an acetamide the pentasaccharides were obtained in four and five steps, respectively.

Four-component one-pot synthesis of a branched manno-pentasaccharide: tert-butyldiphenylsilyl ether as an in situ removable carbohydrate-protecting group

A branched mannose-pentasaccharide was synthesized in a convergent one-pot sequence involving chemo- and regioselective glycosylations of suitable acceptors and in situ removal of tert-butyldiphenylsilyl group. The process demonstrated that a combination of TMSOTf and TfOH can be used as an effective reagent for the fast and selective in situ de-protection of tert-butyldiphenylsilyl group, and also serve as part of the promoter system for the subsequent glycosylation reaction.

Completely encapsulated oligothiophenes up to 12-mer

A series of oligothiophenes covered with tert-butyldiphenylsilyl (TBDPS) groups was synthesized, and the spectroscopic measurements and X-ray analyses revealed that the oligothiophene backbone is completely encapsulated by bulky TBDPS groups.

Synthesis, Biophysical Characterization, and Anti-HIV Activity of Glyco-Conjugated G-Quadruplex-Forming Oligonucleotides

Novel hybrid oligonucleotides carrying the G-quadruplex-forming d(5'TGGGAG3') sequence, conjugated with mono- or disaccharides at the 3' or 5'-end through phosphodiester bonds, have been synthesized as potential anti-HIV agents, via a fully automated, online phosphoramidite-based solid-phase strategy. CD-monitored thermal denaturation studies on the resulting quadruplexes indicated the insertion of a single monosaccharide at the 3'-end as the optimal modification, conferring improved stability to the quadruplex complex. In addition, the 3'-conjugation with glucose or mannose converted the anti-HIV inactive unmodified oligomer into active compounds. On the contrary, the 5'-tethering with these monosaccharides, as well as the conjugation, either at the 5' or 3'-end, with sucrose, were in all cases detrimental to quadruplex stability and did not improve the biological activity. On the basis of the assumption that the kinetically and thermodynamically favored formation of the quadruplex complex is a prerequisite for efficient antiviral activity, a novel bis-conjugated oligonucleotide was designed. This combined a mannose residue at the 3'-phosphate end with bulky aromatic tert-butyldiphenylsilyl (TBDPS) group at the 5'-end, previously shown to markedly favor the formation of quadruplex complexes. The 5',3'-bis-conjugated 6-mer, for which a detailed biophysical characterization has been carried out, resulted in 3-fold greater antiviral activity against HIV-1 than the sole 3'-glyco-conjugated oligonucleotide.

N-Silyl Protecting Groups for Labile Aziridines: Application toward the Synthesis ofN-H Aziridinomitosenes

Hindered N-silylamines were examined for their utility to serve as protecting groups for the labile aziridine nitrogen found within the highly sensitive aziridinomitosene framework. tert-Butyldiphenylsilyl and modified tert-butyldiphenylsilyl groups were the most resistant to nitrogen-silicon bond cleavage under various reaction conditions and were thus employed in transformations relevant to aziridinomitosene synthesis. The N-silylaziridines 7a, 21a, and 21b underwent azomethine ylide cycloaddition and afforded, upon deprotection, the N-H aziridine 24 in 18-32% overall yield for the three steps.

Differential O-3/O-4 regioselectivity in the glycosylation of α and β anomers of 6-O-substituted N-dimethylmaleoyl-protected d-glucosamine acceptors

An assessment of the relative O-3/O-4 reactivities of both methyl α- and β- d-glycosides of N-dimethylmaleoyl (DMM) d-glucosamine acceptors protected at O-6 with benzoyl (Bz), benzyl (Bn), and tert-butyldiphenylsilyl (TBDPS) groups is presented using per-O-benzoylated β- d-galactofuranosyl and per-O-acetylated α- d-galactopyranosyl trichloroacetimidates as glycosyl donors. Using the former donor, the α anomer of the 6-O-benzoylated compound gave exclusive substitution at O-3, whereas the other two compounds with α-configuration kept this site as preferential. The β anomer of the 6-O-benzoylated compound gave the same amounts of reaction products on O-3 and O-4, whereas the other β analogs carried a more reactive O-4. The same reactions were carried out using as donor the less-reactive per-O-acetylated α- d-galactopyranosyl trichloroacetimidate. Although the same trend was found to occur, the O-4 was always relatively more reactive with the pyranosyl donor than with the furanosyl donor, when keeping the remaining factors constant. Furthermore, the β anomers of the acceptor gave almost exclusive substitution at O-4. These observations confirm and extend the utility of these ‘matching’ donor and acceptor reactivities.