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Benzazoles (Bz) and derivatives are interesting molecules in medicinal chemistry. Several of these compounds display diverse biological activities; some are still used in clinical applications. In this way, synthetic chemists are interested in developing new procedures to access compounds with the guanidine moiety as 2-aminobenzimidazole (2ABI), Astemizole (antihistaminic), Albendazole (anthelmintic) and Carbendazim (fungicide). The guanidine group, considered a super base bonded to a benzoxazole ring, results in the 2-guanidinobenzazoles (2GBZs), which could modify the biological activity of these heterocycles. On these bases, we prepared this review article, which covers chemical aspects of 2-guanidinobenzoazoles as potential therapeutic agents and summarizes the current knowledge on the mechanism of pharmacological activities such as cytotoxic, inhibition of cell proliferation via angiogenesis and apoptosis. Specifically, it highlights the most recent results of synthetic approaches to 2GBZs with variety of modifications and functionalization with aromatic, carbohydrate, and amino-acid moieties as illustrated on 28 schemes and is concluded with 141 references. Additionally, the format of this interesting review is exclusively designed on specifically classified category of chemical reactions with primary precursors such as o-substituted anilines and 2-aminobenzazoles (2ABZs). This will constitute the important goals and novelty of this paper to facilitate synthetic chemists in the investigation about development of new pharmacophores., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Benzimidazole (BI) and its derivatives are interesting molecules in medicinal chemistry because several of these compounds have a diversity of biological activities and some of them are even used in clinical applications. In view of the importance of these compounds, synthetic chemists are still interested in finding new procedures for the synthesis of these classes of compounds. Astemizole (antihistaminic), Omeprazole (antiulcerative), and Rabendazole (fungicide) are important examples of compounds used in medicinal chemistry containing BI nuclei. It is interesting to observe that several of these compounds contain 2-aminobenzimidazole (2ABI) as the base nucleus. The structures of 2ABI derivatives are interesting because they have a planar delocalized structure with a cyclic guanidine group, which have three nitrogen atoms with free lone pairs and labile hydrogen atoms. The 10-π electron system of the aromatic BI ring conjugated with the nitrogen lone pair of the hexocyclic amino group, making these heterocycles to have an amphoteric character. Synthetic chemists have used 2ABI as a building block to produce BI derivatives as medicinally important molecules. In view of the importance of the BIs, and because no review was found in the literature about this topic, we reviewed and summarized the procedures related to the recent methodologies used in the N-substitution reactions of 2ABIs by using aliphatic and aromatic halogenides, dihalogenides, acid chlorides, alkylsulfonic chlorides, carboxylic acids, esters, ethyl chloroformates, anhydrides, SMe-isothioureas, alcohols, alkyl cyanates, thiocyanates, carbon disulfide and aldehydes or ketones to form Schiff bases. The use of diazotized 2ABI as intermediate to obtain 2-diazoBIs was included to produce Nsubstituted 2ABIs of pharmacological interest. Some commentaries about their biological activity were included., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)