Thomas P. Brady

A central strategy for converting natural products into fluorescent probes

A Central Strategy for Converting Natural Products into Fluorescent Probes Matthew D. Alexander, Michael D. Burkart, Michael S. Leonard, Padma Portonovo, Bo Liang, Xiaobin Ding, Madeleine M. Joulli!, Brian M. Gulledge, James B. Aggen, A. Richard Chamberlin, Joel Sandler, William Fenical, Jian Cui, Santosh J. Gharpure, Alexei Polosukhin, Hai-Ren Zhang, P. Andrew Evans, Adam D. Richardson, Mary Kay Harper, Chris M. Ireland, Binh G. Vong, Thomas P. Brady, Emmanuel A. Theodorakis, and James J. La Clair*

Phospholipid-bound molecular rotors: synthesis and characterization.

Molecular rotors are fluorescent molecules with a viscosity-sensitive quantum yield that are often used to measure viscosity changes in cell membranes and liposomes. However, commercially available molecular rotors, such as DCVJ (1) do not localize in cell membranes but rapidly migrate into the cytoplasm leading to unreliable measurements of cell membrane viscosity. To overcome this problem, we synthesized molecular rotors covalently attached to a phospholipid scaffold. Attaching the rotor group to the hydrophobic end of phosphatidylcholine (PC) did not affect the rotors viscosity sensitivity and allowed adequate integration into artificial bilayers as well as complete localization in the plasma membrane of an endothelial cell line. Moreover, these new rotors enabled the monitoring of phospholipid transition temperature. However, attachment of the rotor groups to the hydrophilic head of the phospholipid led to a partial loss of viscosity sensitivity. The improved sensitivity and exclusive localization in the cell plasma membrane exhibited by the phospholipid-bound molecular rotors suggest that these probes can be used for the study of membrane microviscosity.

Synthesis of Fused Tetrahydrofuran‐γ‐lactone Motifs via One‐Pot Ring Expansion of Cyclopropane Rings

Abstract An efficient method for constructing fused tetrahydrofuran‐γ‐lactone scaffolds, such as 8, is presented. Key to this strategy is an acid‐catalyzed ring expansion of cyclopropyl precursor 6 that proceeds in the presence of MeSO3H in acetone and produces the desired bicyclic system in good to excellent yields.

Chemical biology studies on norrisolide.

The cellular activity of norrisolide (7), a novel Golgi-vesiculating agent, was dissected as function of its chemical structure. This natural product induces irreversible vesiculation of the Golgi membranes and blocks protein transport at the level of the Golgi. The Golgi localization and fragmentation effects of 7 depend on the presence of the perhydroindane core, while the irreversibility of fragmentation depends on the acetyl group of 7. We show that fluorescent derivatives of norrisolide are able to localize to the Golgi apparatus and represent important tools for the study of the Golgi structure and function.

Synthesis and biological activity of medium molecular weight polymers of camptothecin

A new monomer, 3,6-endo-methylene-1,2,3,6-tetrahydrophthalimidohexanoylcamptothecin (ETHCPT) was synthesized from 3,6-endo-methylene-1,2,3,6-tetrahydrophthalimidohexanoic acid. Its homopolymer and copolymer with acrylic acid (AA) were synthesized and spectroscopically characterized. The ETHCPT content in poly(ETHCPT-coAA) obtained by elemental analysis was 37 wt.%. The number-average molecular weights of the polymers determined by gel permeation chromatography were as follows: Mn ¼ 9700 for poly(ETHCPT), Mn ¼ 25 500 for poly(ETHCPT-coAA). The IC50 value of ETHCPT and its polymers against cancer cells was much larger than that of CPT. The in vivo antitumor activity of all polymers in Balb/C mice bearing the sarcoma 180 tumor cell line was greater than that of CPT at a dose of 100 mg/kg. 2002 Elsevier Science Ltd. All rights reserved.