Palladium-Mediated Synthesis of a Near-Infrared Fluorescent K Sensor.

Potassium (K) exits electrically excitable cells during normal and pathophysiological activity. Currently, K-sensitive electrodes and electrical measurements are the primary tools to detect K fluxes. Here, we describe the synthesis of a near-IR, oxazine fluorescent K sensor (K-1) with a dissociation constant suited for detecting changes in intracellular and extracellular K concentrations.

4,4'-Bismoschamine: biomimetic synthesis and evidence to support structural equivalency to montamine.

The dimeric natural product montamine was originally reported as two N-feruloylserotonin (moschamine) units linked by a nitrogen-nitrogen bond, but our recent synthesis of this symmetrical diacyl hydrazide structure revealed this to be incorrect. We subsequently hypothesized that the moschamine subunits were linked through the indole C4 site and that montamine was structurally identical to 4,4'-bismoschamine, a known natural product present in safflower oil. However, given that authentic samples of both montamine and 4,4'-bismoschamine were unavailable and that the NMR data for the natural products were recorded in different solvents, we were unable to unequivocally prove this hypothesis.

Total synthesis of putative montamine and a proposed structural reassignment.

The natural product montamine was originally assigned as a homodimer of moschamine linked by a N-N' bond at the serotonin side-chain. A total synthesis of the reported structure has shown this to be incorrect. Analysis of the spectroscopic data suggests that the dimerization site has been incorrectly assigned, and montamine is likely to be a 4,4'-bismoschamine natural product previously described in the literature.