Preparation of Novel Molecular Tweezers based on 3,6-O-(2-acylhydrazinocarbonyl) Esters of Hyodeoxycholic acid using Microwave Irradiation

Microwave-Assisted Synthesis of Bile Acids Derivatives: An Overview

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The first attempts at microwave-assisted (MW) syntheses of bile acid derivatives were performed in domestic MW appliances. However, the reproducibility of these syntheses, which were performed in uncontrolled conditions, was very low. In the first part of this overview, compounds synthesized under such conditions are presented. Consequently, with the development of MW technology, MW-assisted reactions in MW reactors became reproducible. Thus, in the second part of this review, syntheses of bile acidsbased compounds in MW reactors are presented. Among others, publications dealing with the following topics will be covered:

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− Chemical transformations of hydroxyl and/or carboxyl functions of bile acids into esters or amides,

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− Hydroxyl group oxidations,

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− Derivatization of oxo-compounds with different nitrogen-containing compounds (e.g. 4-amino-3- substituted-1H-1,2,4-triazole-5-thiones, thiocarbohydrazides and thiosemicarbazides)

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Bile acid-based molecular tweezers, capable of stereospecific molecular recognition

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Reactions of hydroxyl functions to give chlorine derivatives, presenting reactive intermediates in substitution reactions with N- or O-containing nucleophilic arylhydrazides, urea derivatives, substituted thiadiazoles or triazoles or amino acid methyl esters, mainly in solvent-free conditions.

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Some of the synthesized compounds expressed antimicrobial potential and/or good recognition properties as artificial receptors for specific amino acids or anions.

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Detailed comparisons between conventional and MW-assisted procedures for chemical transformations of bile acids are given in most of the presented publications. Based on these results, MW irradiation methods are simpler, more efficient, cleaner and faster than conventional synthetic methods, meeting the requirements of green chemistry.

Synthesis of Novel Chiral Cholic Acid-Based Molecular Tweezers Containing Unsymmetrically Disubstituted Urea Units Using Microwave Irradiation

An efficient procedure has been developed for the synthesis of new chiral cholic acid molecular tweezer artificial receptors by linking an unsymmetrically disubstituted urea to methyl deoxycholate via a carbonate chain using microwave irradiation. The structures of these new receptors were confirmed by 1H NMR, IR, MS spectra and elemental analysis. Their binding properties were examined by UV-Vis spectra titration. The preliminary results indicate that these molecular tweezers not only recognised anions, but also showed good enantioselectivity for D-amino acid methyl esters.