Development from biologically active molecules

The imidazole nucleus is often found in biologically active molecules,3 and a large variety of methods have been employed for their synthesis.4 We recently needed to develop a more viable process for the preparation of kilogram quantities of 2,4-disubstituted imidazoles. The condensation of amidines, which are readily accessible from nitriles,5 with a-halo ketones has become a widely used method for the synthesis of 2,4-disubstituted imidazoles. A literature survey indicated that chloroform was the most commonly used solvent for this reaction.6 In addition to the use of a toxic solvent, yields of the reaction varied from poor to moderate, and column chromatography was often required for product isolation. Use of other solvents such as alcohols,7 DMF,8 and acetonitrile9 have also been utilized in this reaction, but yields are also frequently been reported as poor. 

This photolabile protective group was developed for the protection of diols, which could release caged biologically active molecules in biological systems. The acetal is prepared from the aldehyde and a diol (PPTS, toluene, MgS04, reflux) and is cleaved by photolysis at 348 nm in a pH 7.4 buffer. ... 

Cyclic ureas have many applications as intermediates in the preparation of biologically active molecules. The conventional methods involve cyclization of 1,2-diamines with phosgene or oxidative carbonylation of diamines. Varma and coworkers developed a direct synthesis of cyclic ureas from urea and diamines in the presence of ZnO using microwaves. The major advantage of the method is that the reaction is accelerated by exposure to microwave irradiation the byproducts were, moreover, easily eliminated compared with traditional methods [32]. 

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