An efficient and expeditious synthesis of di- and trisubstituted amino-phenyl and -benzyl derivatives of tetrazole and [1,3,4]oxadiazol-2-one

Investigation of Masked N-Acyl-N-isocyanates: Support for Oxadiazolones as Blocked N-Isocyanate Precursors

In contrast to carbon-substituted isocyanates that are common building blocks, N-substituted isocyanates remain underdeveloped and reports on their N-acyl derivatives (i. e. amido-isocyanates) are exceedingly rare. Herein, amido-isocyanates were investigated in the context of syntheses of aza-tripeptide and hydantoins subunits starting from simple bench-stable precursors. A key finding is that the amido-isocyanate formed in situ cyclized to yield an oxadiazolone, and that under suitable reaction conditions this heterocycle is a traceless blocked (masked) N-isocyanate. Using organic bases as catalysts and upon heating, oxadiazolone formation is observed, and various nucleophiles to provide the desired aza-dipeptides or hydantoins in moderate to high yields. Further support for an amido-isocyanate intermediate was obtained using carboxylic acids as nucleophiles, affording N-acylhydrazide products.

I2 mediated synthesis of 5-substituted-3-methyl/benzyl-1,3,4-oxadiazol-2(3H)-ones via sequential condensation/oxidative cyclization and rearrangement

A simple and efficient iodine-assisted protocol for synthesis of 5-substituted-3-methyl/benzyl-1,3,4-oxadiazol-2(3H)-ones has been developed.

Synthesis of fusidic acid bioisosteres as antiplasmodial agents and molecular docking studies in the binding site of elongation factor-G

Structural modifications through bioisosteric approach yielded fusidic acid analogues with 2–35 folds increase in antiplasmodial activity as compared to fusidic acid.

Discovery of a Novel Series of CRTH2 (DP2) Receptor Antagonists Devoid of Carboxylic Acids

Antagonism of the CRTH2 receptor represents a very attractive target for a variety of allergic diseases. Most CRTH2 antagonists known to date possess a carboxylic acid moiety, which is essential for binding. However, potential acid metabolites O-acyl glucuronides might be linked to idiosynchratic toxicity in humans. In this communication, we describe a new series of compounds that lack the carboxylic acid moiety. Compounds with high affinity (K i < 10 nM) for the receptor have been identified. Subsequent optimization succeeded in reducing the high metabolic clearance of the first compounds in human and rat liver microsomes. At the same time, inhibition of the CYP isoforms was optimized, giving rise to stable compounds with an acceptable CYP inhibition profile (IC50 CYP2C9 and 2C19 > 1 μM). Taken together, these data show that compounds devoid of carboxylic acid groups could represent an interesting alternative to current CRTH2 antagonists in development.