Triphenylmethyl Ethers Research Articles

New substituted C-19-andrographolide analogues with potent cytotoxic activities

Andrographolide, the major diterpenoid lactone from Andrographis paniculata, is toxic against cancer cells. In the present study, we investigated the structure-activity relationships (SARs) of 19 andrographolide analogues which were synthesized by modification at the three hydroxyl groups. A number of the andrographolide analogues showed much higher cytotoxic activities than that of the parent compound on cancer cells including P-388, KB, COL-2, MCF-7, LU-1 and ASK cells. SAR studies of the synthetic analogues indicated that the introduction of silyl ether or triphenylmethyl ether group into C-19 of the parent compound led to increase in toxicity against the cancer cells. The 19-O-triphenylmethyl ether analogue 18 showed higher cytotoxic activity than the potent anticancer drug ellipticine, and this analogue may serve as a potential structure lead for the development of new anticancer drugs.

ChemInform Abstract: An Efficient and Selective Method for the Preparation of Triphenylmethyl Ethers of Alcohols and Nucleosides.

AbstractA simple and efficient method for the trityl protection of primary, secondary and tertiary alcohols is presented, involving their reaction with trityl benzyl ethers in a DEAD—Ce(O‐Tf)4 catalyst system.

ChemInform Abstract: Potential Use of Carbocyclic Nucleosides for the Treatment of AIDS: Chemo-Enzymatic Syntheses of the Enantiomers of Carbovir.

The lactam (1R),(4S)-2-azabicyclo[2.2.1]hept-5-en-3-one [(–)-2], derived by whole cell enantio-specific hydrolysis of the racemate was converted into (–)-carbovir (–)-1 in ten steps. Lipase catalysed acetylation of 4-cis-hydroxycyclopent-2-enylmethyl triphenylmethyl ether afforded the optically pure ester (+)-3 and the alcohol (–)-9. The former compound was converted into (+)-carbovir (+)-1 in three steps.

An efficient and selective method for the preparation of triphenylmethyl ethers of alcohols and nucleosides

A very simple and efficient method is described for the protection of alcohols and nucleosides with benzyl monomethoxytrityl and benzyl dimethoxytrityl ethers in the presence of diethylazodicarboxylate and a catalytic amount of ceric triflate. High selectivity was observed for the tritylation of 5′-OH function of nucleosides.

<b>A solvent free and selective method for preparation of triphenylmethyl ethers of alcohols and nucleosides</b>

A very simple and efficient method is described for protection of alcohols and nucleosides with trityl(triphenylmethyl), mono and dimethoxytrityl chlorides in the presence of triethylamine under microwave irradiation. High selectivity was observed for tritylation of 5'-OH function of nucleosides. KEY WORDS : Protection, Trityl chlorides, Microwave irradiation, Nucleosides, Selectivity Bull. Chem. Soc. Ethiop. 2010 , 24(2), 299-304.

Protecting Groups Transfer: Unusual Method of Removal of Tr and Tbdms Groups by Transetherification

The triphenylmethyl (Tr) group undergoes a transfer (transetherification or disproportionation) between the molecules of 5′-O-Tr-2′-deoxynucleosides in a process mediated by anhydrous sulfates of Cu+2, Fe+2, or Ni+2 to yield mixtures of 3′,5′-bis-O-Tr and 3′-O-Tr products. If phenylmethanol is present in a reaction medium, detritylation results with concomitant formation of phenylmethyl triphenylmethyl ether. The behavior of t-butyldimethylsilyl (TBDMS) group in 5′-O-TBDMS-2′-deoxynucleosides is exactly the same. Such type of transetherifications was not observed before for the O-Tr and O-TBDMS groups.

Reaction of P(IV) mono-and dichlorides with alkyldiphenylmethyl or triphenylmethyl ethers

Reaction of P(IV) mono-and dichlorides with alkyldiphenylmethyl or triphenylmethyl ethers

Reaction of acyl halides and P(III) chlorides with alkyl diphenyl(or triphenyl)methyl ethers

Reaction of acyl halides and P(III) chlorides with alkyl diphenyl(or triphenyl)methyl ethers

Reaction of acyl halides with alkyl diphenylmethyl or alkyl triphenylmethyl ethers

Reaction of acyl halides with alkyl diphenylmethyl or alkyl triphenylmethyl ethers

Reaction of the Acetals with TESOTf−Base Combination; Speculation of the Intermediates and Efficient Mixed Acetal Formation

We report here unexpected highly chemoselective deprotection of the acetals from aldehydes. Treatment of acetal compounds from aldehydes with TESOTf-2,6-lutidine or TESOTf-2,4,6-collidine in CH2Cl2 at 0 degrees C followed by H2O workup at the same temperature caused the conversion of the acetal functions to aldehyde functions. The reaction had generality and was applied to many acetal compounds. Study using various bases revealed the reaction and reached the best combination of TESOTf-base. It was very mild and highly chemoselective and proceeded under weakly basic conditions. Then, many functional groups such as allyl alcohol, silyl ether, acetate, methyl ether, triphenylmethyl (Tr) ether, 1,3-dithiolane, methyl ester, and tert-butyl ester could survive under these conditions. Furthermore, this methodology could selectively deprotect the acetals in the presence of ketals as the most characteristic feature, although this chemoselectivity is difficult to achieve by other previously reported methods. A detailed study of the reaction including MS and NMR studies revealed the reaction mechanism for determining the structures of the intermediates, pyridinium-type salts. These intermediates had a weak electrophilicity and were successfully applied to the efficient formation of the mixed acetals in high yields.

Photoaddition of water and alcohols to the anthracene moiety of 9-(2'-hydroxyphenyl)anthracene via formal excited state intramolecular proton transfer.

The title compound undergoes efficient photoaddition of a molecule of a hydroxylic solvent (H(2)O, MeOH, (Me)(2)CHOH) across the 9- and 10-positions of the anthracene moiety to give isolable triphenylmethanol or triphenylmethyl ether type products. The reaction is believed to proceed via a mechanism involving water-mediated formal excited state intramolecular proton transfer (ESIPT) from the phenolic OH to the 10-position of the anthracene ring, generating an o-quinone methide intermediate that is observable by nanosecond laser flash photolysis, and is trappable with nucleophiles. A "water-relay" mechanism for proton transfer seems plausible but cannot be proven directly with the data available. Irradiation in deuterated solvents led to incorporation of one deuterium atom at the methylene position in the photoaddition product, and partial deuterium exchange of the 10-position of recovered starting material, consistent with the proposed formal excited state proton transfer mechanism. The deuterium exchange and photoaddition reach maximum quantum efficiency at approximately 5 M water (in CH(3)CN or CH(3)OH), with no reaction observed in the absence of a hydroxylic solvent, demonstrating the sensitivity of this type of ESIPT to solvent composition.

A Facile and Efficient One‐Step Conversion of Alcohol Triphenylmethyl Ethers to the Corresponding Acetates.

Alcohol triphenylmethyl (trityl) ethers were readily and efficiently transformed into the corresponding acetates by reaction with acetyl bromide. Triphenylmethyl ethers can also be transformed into the corresponding substituted acetates in high yields by the use of various substituted acetyl chlorides combined with sodium iodide.

Triethyl‐ (or Trimethyl‐)Silyl Triflate‐Catalyzed Reductive Cleavage of Triphenylmethyl (Trityl) Ethers with Triethylsilane.

A triphenylmethyl (trityl) ether was reductively and instantaneously cleaved by triethylsilane in the presence of a catalytic amount of TES- (or TMS)-triflate. The reaction conditions are mild enough to achieve reduction in the presence of a variety of acid-sensitive functional groups. Upon a mild acidic treatment of the crude product, the corresponding alcohol is obtained in high yield.

A Facile and Efficient One-Step Conversion of Alcohol Triphenylmethyl Ethers to the Corresponding Acetates

Alcohol triphenylmethyl (trityl) ethers were readily and efficiently transformed into the corresponding acetates by reaction with acetyl bromide. Triphenylmethyl ethers can also be transformed into the corresponding substituted acetates in high yields by the use of various substituted acetyl chlorides combined with sodium iodide.

Triethyl- (or trimethyl-)silyl triflate-catalyzed reductive cleavage of triphenylmethyl (trityl) ethers with triethylsilane.

[reaction: see text] A triphenylmethyl (trityl) ether was reductively and instantaneously cleaved by triethylsilane in the presence of a catalytic amount of TES- (or TMS)-triflate. The reaction conditions are mild enough to achieve reduction in the presence of a variety of acid-sensitive functional groups. Upon a mild acidic treatment of the crude product, the corresponding alcohol is obtained in high yield.

ChemInform Abstract: Efficient and Catalytic Deprotection of Triphenylmethyl Ethers with Ce(OTf)4.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Efficient and catalytic deprotection of triphenylmethyl ethers with Ce(OTf) 4

A very simple and efficient method is described for deprotection of trityl, mono and dimethoxytrityl ethers using catalytic amount of ceric triflate in acetonitrile under mild reaction conditions. High reactivity was observed for detritylation of saturated and benzylic ethers and also for structurally different nucleosides.

ChemInform Abstract: A Convenient One-Step Method for the Deprotection and Esterification of Triphenylmethyl Ethers.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A convenient one-step method for the deprotection and esterification of triphenylmethyl ethers

We have discovered a simple one-pot procedure to convert trityl ethers into esters, using the corresponding acid chloride as the only reagent.

4‐methoxy substituted trityl groups in 6‐O protection of cellulose: Homogeneous synthesis, characterization, detritylation

AbstractThe reaction of cellulose with methoxy‐substituted triphenylmethyl chlorides under homogeneous conditions in the presence of pyridine was carried out with the aim to develop new protective groups for cellulose simply introducable and completely removable under mild conditions. The obtained cellulose ethers dissolve well in solvents such as N,N‐dimethylformamide, N,N‐dimethylacetamide, dimethyl sulfoxide, 1,4‐dioxane and tetrahydrofuran and show a high 6‐O selectivity. The study proves that the speed of tritylation as well as of detritylation increases in the order unsubstituted trityl/monomethoxytrityl/dimethoxytrityl/trimethoxytrityl. The substituent distribution of the methoxy‐substituted triphenylmethyl ethers of cellulose was determined by means of 13C NMR spectroscopy of the polymers and by high‐performance liquid chromatography after chain‐degradation. Since the methoxy substituted trityl groups were introduced faster and removed easier than the unsubstituted trityl group, they are, therefore, useful tools for a regioselective synthesis of 2,3‐functionalized cellulose derivatives.