Taotao Ling

New fluorescent probes for the measurement of cell membrane viscosity

BACKGROUND Molecular rotors are fluorescent molecules that exhibit viscosity-dependent fluorescence quantum yield, potentially allowing direct measurements of cell membrane viscosity in cultured cells. Commercially available rotors, however, stain not only the cell membrane, but also bind to tubulin and migrate into the cytoplasm. We synthesized molecules related to 9-(dicyanovinyl)-julolidine (DCVJ), which featured hydrocarbon chains of different length to increase membrane compatibility. RESULTS Longer hydrocarbon chains attached to the fluorescent rotor reduce the migration of the dye into the cytoplasm and internal compartments of the cell. The amplitude of the fluorescence response to fluid shear stress, known to decrease membrane viscosity, is significantly higher than the response obtained from DCVJ. Notably a farnesyl chain showed a more than 20-fold amplitude over DCVJ and allowed detection of membrane viscosity changes at markedly lower shear stresses. CONCLUSIONS The modification of molecular rotors towards increased cell membrane association provides a new research tool for membrane viscosity measurements. The use of these rotors complements established methods such as fluorescence recovery after photobleaching with its limited spatial and temporal resolution and fluorescence anisotropy, which has low sensitivity and may be subject to other effects such as deformation.

Antimalarial Evaluation of the Chemical Constituents of Hairy Root Culture of Bixa orellana L.

Over 216 million malaria cases are reported annually worldwide and about a third of these cases, primarily children under the age of five years old, will not survive the infection. Despite this significant world health impact, only a limited number of therapeutic agents are currently available. The lack of scaffold diversity poses a threat in the event that multi-drug–resistant strains emerge. Terrestrial natural products have provided a major source of chemical diversity for starting materials in many FDA approved drugs over the past century. Bixa orellana L. is a popular plant used in South America for the treatment of malaria. In search of new potential therapeutic agents, the chemical constituents of a selected hairy root culture line of Bixa orellana L. were characterized utilizing NMR and mass spectrometry methods, followed by its biological evaluation against malaria strains 3D7 and K1. The crude extract and its isolated compounds demonstrated EC50 values in the micromolar range. Herein, we report our findings on the chemical constituents of Bixa orellana L. from hairy roots responsible for the observed antimalarial activity.

Synthesis of a novel family of diterpenes and their evaluation as anti-inflammatory agents.

The synthesis and biological evaluation of a new family of diterpenes, represented by structures 2 and 3, is presented. These compounds constitute isomeric analogues of acanthoic acid (1) and were examined as potent anti-inflammatory agents. Among them, methyl ester 12 exhibited a low non-specific cytotoxicity, inhibited TNF-alpha synthesis and displayed good specificity in suppressing cytokine expression.

Scalable and Divergent Total Synthesis of (+)-Colletoic Acid, a Selective 11β-Hydroxysteroid Dehydrogenase Type 1 Inhibitor

An efficient and divergent total synthesis of (+)-colletoic acid, a selective 11-β hydroxysteroid dehydrogenase 1 (11-βHSD1) inhibitor, is presented along with its biological activity at the whole-cell level. A scalable, asymmetric synthetic strategy was designed featuring a diversity-oriented synthesis utilizing a diastereoselective intramolecular 5-exo-Heck reaction as the key step to provide the quaternary spirocenter intermediate 9 in multigram scale, thus establishing a platform for further structure-activity relationship studies and providing access to other acorane family members.

Stereoselective synthesis of the fully functionalized core fragment of terpentecin

Abstract A stereoselective synthesis of the core fragment 4 of terpentecin is presented. The five contiguous asymmetric centers of 4 were prepared from enone 8 via a sequence of steps highlighted by: oxygenation of the C6 center by epoxidation of enone 18 , methylenation of the C8 carbonyl group of 20 by means of the Peterson olefination, stereoselective construction of the C8 center of 21 using homogeneous catalytic hydrogenation and stereoselective oxygenation of the C7 center.

Chapter 4 Quinone sesquiterpenes: A challenge for the development of a new synthetic methodology

Publisher Summary This chapter details a synthesis of ilimaquinone that led to develop a new strategy and demonstrate further the synthetic applicability of the underexplored Bartons radical decarboxylation. It also discusses the way primary and secondary carbon radicals can react with quinines to form addition products in effective to excellent yields. This addition reaction is characterized by a well-chemoselectivity, taking place only at conjugated and unsubstituted double bonds, and regioselectivity, being influenced by the resonance effect of heteroatoms located on the quinone ring. The evaluation of the scope and limitations of this method allows devising and executing a unified synthesis of several quinone sesquiterpenes. A characteristic of this strategy is that the quinone unit is attached onto a fully functionalized decalin ring toward the end of the synthesis. As such, it is applicable to a parallel synthesis of these and related compounds and provides a new alternative to the previously known synthetic strategy for related molecules.