Biomedical subjects

Chitra Sundararajan

Publications and source records attributed to Chitra Sundararajan.

7 recordsLinked to original sources

PubMed2006

Design, synthesis, and anti-inflammatory activity both in vitro and in vivo of new betulinic acid analogues having an enone functionality in ring A.

Fifteen new betulinic acid analogues were designed, synthesized, and tested for anti-inflammatory activity. Many of these analogues effectively suppress nitric oxide (NO) production in RAW cells stimulated with interferon-gamma. Analogue 10 is highly and orally active in vivo for induction of the anti-inflammatory and cytoprotective enzyme, heme oxygenase-1.

Animals↗

PubMed2006

Synthesis of a novel dicyano abietane analogue: a potential antiinflammatory agent.

From a structure-activity relationship perspective, the new abietane 5 having cyano groups at C-2 and C-13 and a phenolic ring C has been synthesized and evaluated biologically because the related compound 4 has high potency in inflammation models in vitro and in vivo. Compound 5 was synthesized from 8, which was obtained in five steps from the known compound 9, via an unexpected aromatization caused by the addition of PhSeCl and subsequent oxidation/elimination of the selenated intermediate 14 with H2O2.

Abietanes↗

PubMed2005

Photorelease of carboxylic and amino acids from N-methyl-4-picolinium esters by mediated electron transfer.

One electron reduction of N-alkyl-4-picolinium (NAP) esters initiates C-O bond scission releasing a carboxylate anion. Previous experiments have demonstrated that this process can be initiated by photoinduced electron transfer from an electron-donating sensitizer. In the present study it is demonstrated that a comparable photorelease process can be initiated by photolysis of an electron acceptor (mediator), which in turn abstracts an electron from a ground state electron donor. The resulting mediator anion radicals donate an electron to the NAP ester, triggering release of the carboxylate anion. It is demonstrated that when benzophenone is used as a mediator, higher quantum yields for ester decomposition can be achieved compared with sensitizers that do direct photoinduced electron transfer.

Amino Acids↗

PubMed2005

Photolytic release of carboxylic acids using linked donor-acceptor molecules: direct versus mediated photoinduced electron transfer to N-alkyl-4-picolinium esters.

[reaction: see text] Efficient photorelease (Phi = 0.7) of carboxylic acids is achieved with a covalently linked mediator (benzophenone) protecting group (N-alkyl-4-picolinium ester) molecule. The mechanism involves initial photoreduction of the mediator, followed by rapid electron transfer to the protecting group.

Journal Article↗

PubMed2005

Photorelease of carboxylic acids, amino acids, and phosphates from N-alkylpicolinium esters using photosensitization by high wavelength laser dyes.

Visible light (>450 nm) is used to efficiently cleave carboxylic acids, amino acids, and phosphates from their N-methyl picolinium esters. Photolysis using pyrromethene dyes PM 546 and PM 597 and also coumarin 6 as photosensitizers effects release of carboxylic acids, N-protected amino acids, and phosphates in quantitative yields. The effective rate of photorelease by the dyes, Phiepsilon, was found to be as high as 4500 M-1 cm-1. The photorelease proceeds through photoinduced electron transfer from the dye sensitizers to the N-methyl picolinium group. Fluorescence quenching and laser flash photolysis experiments support the photoinduced electron-transfer mechanism.

Amino Acids↗

PubMed2004

C-O bond fragmentation of 4-picolyl- and N-methyl-4-picolinium esters triggered by photochemical electron transfer.

Photochemical reduction of several 4-picolyl- and N-methyl-4-picolinium esters was examined using product analysis, laser flash photolysis, and fluorescence quenching. It is demonstrated that the radical (anions) formed in these reactions readily fragment to yield a carboxylic acid and a 4-pyridylmethyl radical intermediate. The high chemical and quantum yields observed for these photoreactions suggests that these esters can be used as photolabile protecting groups.

Journal Article↗

PubMed2004

Photoremovable protecting groups based on electron transfer chemistry.

Photoremovable protecting groups (also known as photolabile protecting groups, phototriggers, or caged molecules) are functional groups that are attached to a molecule in such a way as to render the latter inactive. Exposure to light releases the protecting group, restoring functionality to the molecule. The use of photoremovable protecting groups (PRPGs) allows for precise spatial and temporal control of chemical reactions. Such groups have found use in many diverse applications, ranging from time resolved studies of physiological processes, to fabrication of spatially resolved combinatorial libraries of DNA. Recent research efforts have focused on designing protecting groups that are removed through photoinduced electron transfer (PET), rather than by direct photolysis. The PET strategy allows the light absorption step to be decoupled from the bond breaking step, thus permitting more control over the wavelengths of light used in the release process. The application of these types of protecting groups to the photochemical release of amines, alcohols, ketones, and carboxylic acids is described.

Journal Article↗