Base-Catalyzed Phenol-Mannich Condensation of Preformed Cesium Iminodiacetate. The Direct Synthesis of Calcein Blue AM and Related Acyloxymethyl Esters.

A rapid and highly practical one-flask procedure for the preparation of (acyloxy)methyl -(2-hydroxybenzyl)iminodiacetate and related diesters from iminodiacetic acid and phenols is described. The key to this multicomponent phenol-Mannich condensation resides in the use of cesium iminodiacetate as the reaction partner. This protocol has been applied in an unusually direct synthesis of the intracellular fluorescent dye Calcein blue AM, for which scant experimental and spectroscopic data are presently available.

Stepwise PEG synthesis featuring deprotection and coupling in one pot.

The stepwise synthesis of monodisperse polyethylene glycols (PEGs) and their derivatives usually involves using an acid-labile protecting group such as DMTr and coupling the two PEG moieties together under basic Williamson ether formation conditions. Using this approach, each elongation of PEG is achieved in three steps - deprotection, deprotonation and coupling - in two pots. Here, we report a more convenient approach for PEG synthesis featuring the use of a base-labile protecting group such as the phenethyl group.

Near-Infrared Hybrid Rhodol Dyes with Spiropyran Switches for Sensitive Ratiometric Sensing of pH Changes in Mitochondria and melanogaster First-Instar Larvae.

Near-infrared hybrid rhodol dyes (probes and ) for sensitive ratiometric visualization of pH changes were prepared by incorporating hemicyanine dyes into traditional rhodol dyes. This approach was based on -conjugation changes involving a rhodol hydroxyl group as a spiropyran switch upon pH changes. Electronic spectra of probes - and - contain sharp absorption peaks at 535 nm and fluorescence peaks at 558 nm with similar -conjugation and a closed spiropyran form at a basic pH of 10.

A FRET-Based Near-Infrared Fluorescent Probe for Ratiometric Detection of Cysteine in Mitochondria.

We report a near-infrared fluorescent probe A for the ratiometric detection of cysteine based on FRET from a coumarin donor to a near-infrared rhodamine acceptor. Upon addition of cysteine, the coumarin fluorescence increased dramatically up to 18-fold and the fluorescence of the rhodamine acceptor decreased moderately by 45 % under excitation of the coumarin unit. Probe A has been used to detect cysteine concentration changes in live cells ratiometrically and to visualize fluctuations in cysteine concentrations induced by oxidation stress through treatment with hydrogen peroxide or lipopolysaccharide (LPS).

A Near-Infrared Fluorescent Probe Based on a FRET Rhodamine Donor Linked to a Cyanine Acceptor for Sensitive Detection of Intracellular pH Alternations.

A fluorescence resonance energy transfer (FRET)-based near-infrared fluorescent probe () for double-checked sensitive detection of intracellular pH changes has been synthesized by binding a near-infrared rhodamine donor to a near-infrared cyanine acceptor through robust C-N bonds via a nucleophilic substitution reaction. To demonstrate the double-checked advantages of probe , a near-infrared probe () was also prepared by modification of a near-infrared rhodamine dye with ethylenediamine to produce a closed spirolactam residue. Under basic conditions, probe shows only weak fluorescence from the cyanine acceptor while probe displays nonfluorescence due to retention of the closed spirolactam form of the rhodamine moiety.