Organic & Biomolecular Chemistry Blog

Not many molecules can claim to be both a Michael donor and Michael acceptor while containing a good leaving group as is the case with nitroketene-N,S-acetals like N-methyl-S-methyl nitroethylene (NMSM), broadly categorized as nitroenamines.

As a double actor in the pseudo three-component reaction investigated by Rao and Parthiban, moieties of NMSM react three times in two roles:  twice as a nucleophile and once as an electrophile.  The other components in the same pot included the aromatic aldehyde and catalytic 2-aminopyridine.

The methodology generates an alternate route from the classic Hantzsch reaction to the 1,4-dihydropyridine (DHP) platform with a broader scope and purification by recrystallization.  Advantageously, 1,4-DHPs are calcium channel blockers and hydride sources for reduction.

The functionally-rich NMSM component conveniently diversifies DHP which could lead to more potent medicinal applications or pesticides.

The two inherent diversity points on the platform arose from the aldehyde and amine precursors.  Additional diversity from amine substitution of the built-in sulfide leaving group created a total of 29 unique 1,4-DHP possibilities.

Specifically, they synthesized a neonictinoid insecticide analogue to the popular nitenpyram compound to constrain the alkene to the cis-isomer with muted toxicity to mammals.

Overall, leveraging an electronically versatile synthon like NMSM in a multicomponent reaction leads to enhanced diversity for analoging with myriad compounds that could perform better than those currently available.

To find out more see:

One-pot pseudo three-component reaction of nitroketene-N,S-acetals and aldehydes for synthesis of highly functionalized hexa-substituted 1,4-dihydropyridines
H. Surya Prakash Rao and A. Parthiban
DOI: 10.1039/c4ob00628c

Jennifer Lee is currently a Ph.D. candidate in Dr. George Kraus’ organic chemistry lab at Iowa State University.  Her research focuses on designing methodologies to transform carbohydrate-derived biomass into biorenewable commodity and specialty chemicals.  The creation of a versatile platform technology led to diverse and industrially-relevant aromatic compounds to work toward a more sustainable future.

Many human activities have been responsible for heavy metal poisoning in recent years, Mercury (Hg) poisoning being one of them. Mercury occurs in several forms and even trace concentrations of mercury ions in crops, fish or the human body are enough to produce potentially toxic effects to vital organs. Mercury poisoning can lead to several diseases including Acrodynia (also known as the pink disease), the Hunter-Russell syndrome and the Minamata disease.

Selective detection of mercury, particularly in aqueous media, has been a key area for analytical chemists, since traditional analytical techniques for mercury detection are time consuming, laborious and involve expensive instrumentation. In this work, Korean researcher Keun-Hyeung Lee and co-workers have developed a pair of very sensitive amino acid based fluorescence-ON probes for the exclusive detection of mercury ions in aqueous solution.

The team has combined the fluorescence properties of pyrene and Hg(II) binding ability of tyrosine residues for the design and synthesis of two novel fluorescensors. Both newly-synthesised probes show emission maxima at 386 and 400 nm in the absence of Hg(II) ion. Upon titration with Hg(II) ions, both probes show exponential fluorescence enhancement and display a remarkable red shift (90-100 nm) emission. These probes are also highly selective for mercury ions in the presence of a range of other metal ions and are effective in aqueous solutions.

The team further clarifies the binding mode of these sensors and the coordination of the metal ion. This method can be implemented for rapid and quantitative detection of Hg(II) from various polluted water sources. This work also underscores the unconventional use of an amino acid as a chemosensor.

Ratiometric fluorescence chemosensor based on tyrosine derivatives for monitoring mercury ions in aqueous solutions
Ponnaboina Thirupathi, Ponnaboina Saritha (née Gudellin) and Keun-Hyeung Lee
DOI: 10.1039/C4OB01044B