Trimethylsilyl Ethyl Research Articles

Synthesis of the Branched Tetrasaccharide Repeating Unit ofLactobacillus fermentumTDS030603 and Its Regioisomer

The branched tetrasaccharide repeating unit β-Glc-(1→3)-[α-Glc-(1→6)-α-Gal-(1→2)]-Glc of Lactobacillus fermentum TDS030603 was synthesized. In addition, its regioisomer β-Glc-(1→2)-[α-Glc-(1→6)-α-Gal-(1→3)]-Glc was synthesized for a future assay study. In these syntheses, we examined di-n-butyl phosphate (DBP) and phenylthio (SPh) groups as leaving groups for glycosidation and examined p-methoxyphenyl (MP) and 2-(trimethylsilyl)ethyl (TMSEt) groups as acceptor-reducing end anomeric protecting groups. In the selective synthesis of the target tetrasaccharide repeating unit, the combination of MP acceptors and DBP donors was effective, achieving regio- and stereo-selective glycosidation. However, purification after removal of the MP group in the final step proved difficult. Nevertheless, we achieved simultaneous synthesis of both the branched tetrasaccharide repeating unit and its regioisomer in high yield using a combination of TMSEt acceptors and SPh donors.

Tip enhanced Raman spectroscopy, DFT and PED calculations of 4″-trimethylsilylethylsulfanyl-4,4′-di(phenyleneethynylene)benzene thiol adsorbed on silver

Monolayers of α,ω-dithiol oligo(phenyleneethynlene) molecules are critical to the field of molecular electronics because of their abilities to form bonds with many metallic surfaces and rectify current. In this study Fourier Transformation-Raman, surface-enhanced Raman scattering (SERS) spectroscopy and Tip-enhanced Raman Spectroscopy (TERS) were used to characterize a selectively oriented self-assembled monolayer of 4″-trimethylsilylethylsulfanyl-4,4′-bis-(phenyleneethynylene)benzenethiol (OPE′) on silver coated nanospheres. Selective orientation was achieved by synthesizing 4″-trimethylsilylethylsulfanyl-4,4′-bis-(phenyleneethynylene)benzene disulfide, which undergoes oxidative dissociation and covalently bonds to the metal surface. The Ag coated nanosphere surfaces were characterized by scanning electron microscopy (SEM), which showed a large area of surface charging. The SERS and TERS spectra show similar results; however, a greater enhancement was achieved with the TERS relative to the SERS spectra. Assignments of vibrational bands were based on DFT calculations performed at the B3LYP level with good agreement between theoretical and experimental values. An average percent difference of 2.5 cm−1 was obtained for the non-CH stretching frequencies and a scaling factor was not applied to theoretically generated frequencies. A red shift of the ν(C–S) peak at 1087 cm−1 was observed when OPE′ was adsorbed on a Ag surface. Vibrations specific to the trimethylsilylethyl (TMSE) group were visible in the TERS spectra, and disappear upon deprotection.

Enantioselective dirhodium(II)-catalyzed cyclopropanations with trimethylsilylethyl and trichloroethyl aryldiazoacetates

Highly functionalized cyclopropanecarboxylates were readily prepared by rhodium-catalyzed cyclopropanation of alkenes with aryldiazoacetates and styryldiazoaceates, in which the ester functionality is either trimethylsilylethyl (TMSE) or trichloroethyl (TCE). By having labile protecting groups on the ester, chiral triarylcyclopropane carboxylate ligands were conveniently prepared. The asymmetric induction during cyclopropanation is dependent on the nature of the ester group and the chiral dirhodium tetracarboxylate catalyst. The prolinate catalyst Rh2(S-DOSP)4 was the optimum catalyst for asymmetric intermolecular cyclopropanation of TMSE diazoesters with styrene, while Rh2(R-BPCP)4 was the optimum catalyst for TCE diazoesters.

An efficient method for the synthesis of selenium modified nucleosides: its application in the synthesis of Se-adenosyl-L-selenomethionine (SeAM).

In this paper, we report that a versatile method for the synthesis of 5'-selenium modified nucleosides has been explored on the basis of a 2-(trimethylsilyl)ethyl (TSE) selenyl group as a selenating donor. We demonstrate the broad utility of this method through direct introduction of various functional groups into 5'-TSE-selenonucleosides. This original method offers additional advantages for the preparation of these compounds, such as high functional group tolerance, ready availability of various electrophilic reagents, mild conditions, simple operation, and good yields. The utility of this approach is further demonstrated by the synthesis of Se-adenosyl-L-selenomethionine (SeAM) as a chemical reporter for methyltransferases.

Efficient Synthetic Approaches To Access Ruthenium(II) Complexes with 2‐(Trimethylsilyl)ethyl‐ or Acetyl‐Protected Terpyridine–Thiols

AbstractA series of thiol‐functionalized terpyridines (tpy) with protective groups, such as acetyl (Ac), 2‐(trimethylsilyl)ethyl (TMSE), and tert‐butyl (tBu), and the corresponding ruthenium(II) complexes were synthesized in high yields. The TMSE‐protected thiol‐functionalized RuII(tpy) complexes can be readily converted into the corresponding ruthenium(II) complexes with an acetyl group by using AgClO4/acetyl chloride or TBAF/acetyl chloride. Based on this convenient synthetic approach under mild conditions, the ruthenium(II) complex [(AcSCH2C6H4tpy)(PPh3)2Ru(C≡CC6H4C≡CC6H5)](ClO4) {[12](ClO4)} with acetylthio–tpy was successfully obtained by a three‐step synthetic procedure. By utilizing 4′‐{4‐[(acetylsulfanyl)methyl]phenyl}‐2,2′:6′,2″‐terpyridine as a chelating ligand, a dinuclear dicyanamido‐linked ruthenium complex was prepared, characterized, and immobilized onto gold electrode surfaces to form self‐assembled monolayers (SAMs). The compounds were characterized by mass spectrometry, IR, 1H NMR and 13C NMR or 31P NMR spectroscopy, and elemental analysis. The solid‐state structure of complex [14](PF6)3 was determined by X‐ray crystallography, in which the intramolecular S⋅⋅⋅S distance was found to be 31.194(2) Å.

Synthesis of Novel Selenapenams, Selenacephems, and Selenazepines Using a 2-(Trimethylsilyl)ethyl Protection Approach

Selenapenams, selenacephems, and selenazepines were synthesized using a 2-(trimethylsilyl)ethyl (TSE) protection approach in an extremely simple way. TSE protection for selenium is used for the first time in the synthesis of selenium-containing beta-lactam. Novel intramolecular cycloaddition reaction of selenium with alkynes and allenes is used in the present synthesis.

Direct Preparation of Nucleoside Vinyl Disulfides from 2-(Trimethylsilyl)ethyl Sulfides, an Access to Vinylthiols

We report here a straightforward preparation of various nucleoside vinyl disulfides in high yields under mild conditions using the new reaction of vinyl 2-(trimethylsilyl)ethyl (TMSE) sulfides with sulfenyl chlorides. This reaction allows the preparation of various mixed disulfides from stable silyl sulfides without formation of oxidizable and/or unstable thiols. The easy preparation of vinyl disulfides through this reaction should offer new perspectives in vinylthiol chemistry.

Fluoride‐Labile Protecting Groups for the Synthesis of Base‐Sensitive Methyl‐SATE Oligonucleotide Prodrugs

AbstractBase‐sensitive methyl‐SATE oligonucleotide prodrugs (prooligos) were synthesized using fluoride‐labile protection groups on the nucleobases and on certain internucleosidic phosphate linkages. The combination of [(tert‐butyl)(diphenyl)silyloxymethyl]benzoyl (SiOMB) and (trimethylsilyl)ethyl (TSE) groups is well adapted for synthesis of these compounds using phosphoramidite chemistry on a solid support. The prooligo was anchored on the support via a phosphoramidate linkage. A final treatment with Et3N·3HF in THF efficiently releases the prooligo from the solid support and cleaves the SiOMB and TSE groups. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Mild deprotection of 2-(trimethylsilyl)ethyl esters

A method for the deprotection of 2-(trimethylsilyl)ethyl (TMSE) esters is described. Treatment of carboxylic esters with NaH in DMF cleanly produces the deprotected acid after extractive work-up. This method can be applied to sterically-hindered substrates as well as esters containing fluoride-labile functionality. A tandem alkylation/ester deprotection procedure is also presented.

A mild and selective method for the cleavage of tert-butyl esters

A method for the cleavage of t-butyl esters using silica gel in refluxing toluene is reported. Good yields of the corresponding carboxylic acids are obtained, and the reaction is selective for t-butyl esters over t-butyl ethers and trimethylsilylethyl (TMSE) esters.

フッ素化合物を中心とする光学活性化合物の不斉合成法の開発

The synthesis of chiral fluorinated molecules is important in the biological and medicinal chemistry fields in view of the influence of fluorine's unique properties on biological activity. In recent years, we have studied asymmetric synthesis focussing on such optically active compounds. This review describes 1) diastereoselective trifluoromethylation of chiral N-acyloxazolidinones, 2) catalytic enantioselective aldol reactions of fluorine-substituted ketene silyl acetals, and 3) catalytic enantioselective allylation of aldehydes mediated by chiral Lewis bases. The trifluoromethylation of lithium enolates of N-acyloxazolidinones with iodotrifluoromethane is mediated by triethylborane to give the corresponding trifluoromethylated products with up to 86% diastereomeric excess. The stereoselective reaction is considered to proceed through the attack of the trifluoromethyl radical on the less hindered face of the lithium imide. Difluoroketene and bromofluoroketene trimethylsilyl ethyl acetals react with various aldehydes in the presence of chiral Lewis acids to afford the corresponding desired aldols with up to 99% enantiomeric excess (ee). It is noteworthy that the aldol reactions of the fluorine-substituted acetals at -78 degrees C and at higher temperatures (-45 or -20 degrees C) provide the (+)- and (-)-aldols, respectively, with excellent-to-good enantioselectivity. Chiral phosphoramides newly prepared from (S)-proline were found to catalyze the allylation and crotylation of aromatic aldehydes with allylic trichlorosilanes in good enantioselective yields (up to 90% ee). (S,S)-Bis(alpha-methylbenzyl)formamide developed as an efficient catalyst for the allylation and crotylation of aliphatic aldehydes mediates the enantioselective addition with the assistance of hexamethylphosphoramide (HMPA) to afford the corresponding homoallylic alcohols in up to 98% ee.

Synthesis of the globotetraose tetrasaccharide and terminal tri- and di-saccharide fragments

The 2-(trimethylsilyl)ethyl (TMSEt) β-glycosides of globotetraose [β- d-GalNAc-(1 → 3)-α- d-Gal-(1 → 4)-β- d-Gal-(1 → 4)- d-Glc] and the terminal trisaccharide, as well as the methyl α-glycoside 1 of the terminal disaccharide, were synthesised by silver trifluoromethanesulfonate-promoted β-glycosylation of suitably protected galactoside, galabioside, and globotrioside alcohols with 3,4,6-tri- O-acetyl-2-deoxy-2-phthalimido-β- d-galactopyranosyl chloride, followed by removal of protecting groups. Removal of the anomeric TMSEt group of the globotetraoside and of the terminal trisaccharide, using trifluoroacetic acid-dichloromethane, gave the corresponding hemiacetal sugars 8 and 3. The TMSEt glycoside of the terminal trisaccharide was converted, via the 1-acetate, into the corresponding isobutyl ( 4) and 3-butylsulfonyl-2-[(butylsulfonyl)methyl]propy] ( 5) glycosides and into the TMSEt thioglycoside 6 via the glycosyl bromide.

2-(trimethylsilyl)ethyl as a phosphate protecting group in oligonucleotide synthesis

The 2-(trimethylsilyl)ethyl (TSE) group was found to be effective as a protecting group for the internucleotidic phosphate in oligonucleotide synthesis. Phosphoramidite building blocks having the TSE group were prepared in good yields. In the case of deoxyguanosine, a 2- N-unprotected phosphoramidite building block was synthesized. These compounds were applied to the solid-phase synthesis of oligodeoxyribonucleotides. A side reaction associated with the unprotected guanine moiety was elucidated by means of 31P NMR.

Synthesis of the Forssman pentasaccharide and terminal tetra-, tri-, and di-saccharide fragments

The 2-(trimethylsilyl)ethyl (TMSEt) β-glycosides of the Forssman pentasaccharide [α- d-GalNAc-(1 → 3)-β- d-GalNAc-(1 → 3)-α- d-Gal-(1 → 4)-β- d-Gal-(1 → 4)- d-Glc] and the terminal tetrasaccharide, as well as the methyl glycosides 1 and 2 of the terminal di- and tri-saccharides, were synthesised by silver trifluoromethanesulfonate-promoted α-glycosylation of suitably protected mono-, di-, tri-, and tetrasaccharide alcohols with 3,4,6-tri- O-acetyl-2-azido-2-deoxy-α- d-galactopyranosyl bromide, followed by removal of protecting groups. The anomeric TMSEt group of the Forssman pentasaccharide and terminal tetrasaccharide was removed with trifluoroacetic acid-dichloromethane, to give the corresponding hemiacetal sugars 4 and 6.

Novel class of silicon‐based protective groups for the side chain of tyrosine

A novel class of silyl-based protective groups compatible with the Bpoc/t-Bu strategy has been developed for the side chain of tyrosine. Carbobenzyloxy (CBZ) and biphenylisopropyloxy (Bpoc)-O-beta-trimethylsilylethyl-tyrosine (10 and 12) and CBZ-O-beta-dimethylphenylsilylethyl-tyrosine 14 were prepared in reasonable yields and in very high purity. The trimethylsilylethyl (TMSE) group proved to be 3-4 times more stable than the tert-butyl ether group towards 0.5% TFA. The latter is removed up to 4% during the acidolysis of the Bpoc group. As expected, the dimethylphenylsilylethyl (DMPSE) group was even more resistant towards 0.5% TFA (five time greater than the TMSE analog). Both silyl protective groups were found to be resistant towards a variety of reagents used in peptide synthesis, such as trialkylamines, hydroxybenzotriazole, trialkylphosphine and nucleophiles. They are readily removed in neat TFA in 5-20 min in the absence of cation scavengers, without any detectable alkylation of the phenolic ring. The application of the new silyl-based protective group was demonstrated by the synthesis of the C-terminal 29 amino acid peptide of the basic pancreatic trypsin inhibitor by the prior thiol capture methodology. The protected octapeptide BocC(Acm)QT)(tBu)FVY(TMSE)GG-PO-dibenzofuranthiol++ + was synthesized by solid-phase peptide synthesis using Bpoc-(O-TMSE)-Tyr-OH in greater than 90% yield and coupled to an unprotected 21-mer. The partially blocked, purified peptide was deprotected quantitatively in neat TFA in 1 h.

2-(Trimethylsilyl)ethyl glycosides. Synthesis of the asialo-GM1-tetrasaccharide, spacer glycoside, and BSA and Sepharose glycoconjugates.

The tri and tetra-saccharide glycosides beta-D-GalNAc-(1-4)-beta-D-Gal-(1-4)-beta-D-Glc-1-OTMSEt and beta-D-Gal-(1-3)-beta-D-GalNAc-(1-4)-beta-D-Gal-(1-4)-beta-D-Glc-1-OT MSEt (asialo-GM1) have been synthesized by sequential glycosylations of a suitably protected 2-(trimethylsilyl)ethyl (TMSEt) lactoside with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-galactopyranosyl chloride and 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl bromide. The tetrasaccharide glycoside was transformed into the corresponding hemiacetal sugar as well as the 1-chloro sugar. The latter was used for glycosylation of 2-bromoethanol. The resulting glycoside was used to alkylate methyl 3-mercaptopropionate and the resulting spacer glycoside was used for the preparation of the title glycoconjugates.

ChemInform Abstract: 2‐(Trimethylsilyl)ethyl Glycosides. Transformation into Glycopyranosyl Chlorides.

2-(Trimethylsilyl) ethyl (TMSET) glycosides were transformed in high yields into the corresponding1-chloro sugars by treatment with 1,1-dichloromethyl methyl ether/zinc chloride. With acetyl, benzoyl, and benzyl protection of the 2-position, the α-glycopyranosyl chloride was the major product, whereas with the 2-phthalimido sugar, a β-chloride was obtained. The fully benzylated TMSET glucopyranoside gave a α-chloro sugar carrying a 6-O-formyl group whereas partially benzylated sugars gave the chloro sugars with all protecting groups intact

2-(Trimethylsilyl)ethyl glycosides. Transformation into glycopyranosyl chlorides

2-(Trimethylsilyl) ethyl (TMSET) glycosides were transformed in high yields into the corresponding1-chloro sugars by treatment with 1,1-dichloromethyl methyl ether/zinc chloride. With acetyl, benzoyl, and benzyl protection of the 2-position, the α-glycopyranosyl chloride was the major product, whereas with the 2-phthalimido sugar, a β-chloride was obtained. The fully benzylated TMSET glucopyranoside gave a α-chloro sugar carrying a 6-O-formyl group whereas partially benzylated sugars gave the chloro sugars with all protecting groups intact

Trimethylsilyl ethyl orthopropiolate - preparation and use as a propiolate anion equivalent

Lithio ethyl orthopropiolate (4b), prepared from trimethylsilyl ethyl orthopropiolate (4a), is introduced as an easy to handle propiolate anion (1a) equivalent.