Novel glucose-derived gemini surfactants with a 1,1′-ethylenebisurea spacer: Preparation, thermotropic behavior, and biological properties

In the search for environmentally safe surfactants made from inexpensive and renewable sources, the interest has mainly been focused on new saccharide derivatives. This report describes the synthesis of newly designed nonionic gemini compounds comprising two reduced sugar headgroups, two alkyl tails, and a 1,1′-ethylenebisurea entity as the spacer linking two amphiphilic glucose-derived moieties. Thus, the series of N,N′-bis[(3-alkyl-3-deoxy-d-glucitol)ureido]ethylenediamines (bis(C_nGT), with C_n=n-C₉H₉, n-C₆-H₁₃, n-C₈H₁₇, n-C₁₀H₂₁, or n-C₁₂H₂₅), were prepared using a convenient procedure starting from easily accessible reagents such as d-glucose, n-alkylamines, urea, and ethylenediamine. Their structure and purity were confirmed by means of elemental analysis, electrospray ionization mass spectrometry, and ¹H and ¹³C nuclear magnetic resonance spectroscopy. Additionally, the present contribution introduces selected properties of these surfactants, including their thermotropic behavior and biological properties. The presence of two phase transition points, determined using the differential scanning calorimetry method, indicates liquid-crystalline mesophase formation upon heating. Furthermore, using the closed-bottle test (OECD Guideline 301D) as well as the biological oxygen demand test for insoluble substances for biodegradability measurements, it has been concluded that the tested glucose-derived gemini structures achieve more than 60% biodegradation after 64–75 test days. All tested surfactants were practically nontoxic to bacteria, yeast, and molds. Owing to their fitting aggregation ability as well as their nontoxicity, they constitute an interesting group of surfactants for various applications.