Chemical Science Blog

A new way to make 2-arylphenols, which are found in organocatalysts, sensors, phosphite ligands, and biologically active substances has been devised by scientists in the US.

Simple and cheap aryl chlorides can be used to directly arylate unprotected phenols without transition metals. This is the first general, regioselective intermolecular phenol ortho-arylation process that uses aryl chlorides as one of the coupling components. It is the most direct synthetic pathway to 2-arylphenols – no protecting group manipulations are required.

The team also made arylated binaphthol derivatives. Additionally, they have presented the shortest pathway to date for the synthesis of helicenes – one step from commercially available reagents.

Read this ‘HOT’ Chemical Science article today:

Divergent Reaction Pathways for Phenol Arylation by Arynes: Synthesis of Helicenes and 2-Arylphenols
T Truong and O Daugulis
Chem. Sci., 2012, DOI: 10.1039/c2sc21288a

Phthalocyanines (Pcs) have excellent electronic and optical properties, which make them promising as a photosensitisers (PSs) for photodynamic therapy (PDT). Since Pcs strongly and selectively absorb light in the range of 600-800nm, they allow high penetration depth of light in normal tissue while minimising the risk and complications such as burning. But Pcs are highly hydrophobic and tend to form aggregates in aqueous media, which reduces their therapeutic activity.

Various types of nanocarriers, such as micelles, liposomes and nanoparticles, have been used to overcome this problem, and to prepare a stable dispersion of Pc in aqueous solution. However, most of them still suffer from shortcomings such as poor loading of Pc (small weight % of Pc in nanocarriers), risk of payload leaking before reaching target cells, and laborious, time-consuming fabrication and encapsulation processes.

Scientists in the Republic of Korea have made ZnPc nanospheres in one pot without using any templates or emulsifiers. They can be post-synthetically modified to improve their dispersibility in aqueous solution without altering their morphology or properties. They show higher singlet oxygen generation efficiency and in vitro phototoxicity than monomeric Pc molecules, suggesting that they are potentially useful as a photosensitiser for photodynamic therapy.

Targeting ligands could be introduced to deliver the nanospheres to specific target sites, anticipate the researchers. And if therapeutic agents were encapsulated, they could perform dual chemo- and photodynamic therapy.

Read this ‘HOT’ Chemical Science article:

Self-assembled, covalently linked, hollow phthalocyanine nanospheres
Raghunandan Hota, Kangkyun Baek, Gyeongwon Yun, Youngkook Kim, Hyuntae Jung, Kyeng Min Park, Eunjin Yoon, Taiha Joo, Juseok Kang, Chan Gyung Park, Su Mi Bae, Woong Shick Ahn and Kimoon Kim
Chem. Sci., 2012, DOI: 10.1039/C2SC21254D

A new method of introducing single-molecule-quality fluorophores into live bacterial cells for superresolution imaging studies has been developed by researchers in the US.

Superresolution imaging can image structures with a spatial resolution 5 to 10 times smaller than the diffraction limit of about 200nm for visible wavelengths. In contrast to previous ideas, the team allows a permeable dye molecule (the substrate) to enter the cell in a fluorescently deactivated state.

Subsequent photoactivation by reaction with the enzyme nitroreductase produces fluorescent products whose concentration is controlled by the level of substrate uptake. Importantly, fluorophores can enter living cells fairly easily because they are neutral, and they emit at long wavelengths to avoid autofluorescence.

Read this ‘HOT’ Chemical Science article today:

Enzymatic Activation of Nitro-Aryl Fluorogens in Live Bacterial Cells for Enzymatic Turnover-Activated Localization Microscopy
Marissa K. Lee, Jarrod Williams, Robert Twieg, Jianghong Rao and W.E. Moerner
Chem. Sci., 2012, DOI: 10.1039/C2SC21074F