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The titled compounds were prepared from 2-amino-5-heptadecyl [1,3,4]thiadiazole (1). Diazotization of (1) produced (2) which was coupled with active methylene compounds and gave azo hydrazono derivatives (3A, 3B) a-d . It was found that there is regio-specificity for addition of different nucleophiles to these tautomers; thus, nitrogen nucleophiles such as hydrazine hydrate, hydroxylamine hydrochloride and thiourea were reacted via Azo tautomer (3A) to yield pyrazole, isoxazole and pyrimidine respectively (5-7), while carbon nucleophiles as phenylisocyanate was reacted via the hydrazono tautomer (3B) and produced triazine derivatives (4). Additionally, the diazonium chloride (2) was coupled with alkaline 2-naphthol and produced 2-(5-heptadecyl-[1,3,4]thiadiazol-2-yl) -1,2-dihydro-3-oxa-1,2-diaza-cyclopenta[a]naphthalene (8). UV-visible spectra of the synthesized colored compounds (2-8) showed k max at 374-398 nm, while screening these compounds in vitro against micro-organisms (including structure-activity relationship SAR study) revealed high antibacterial and moderate antifungal activities. Propoxylation of compounds 1, 3, 5, 6, 7 and 8 with 3, 5, 7 mol of propylene oxide produced nonionic surfactants I(a-c)-IX(a-c) having surface active properties so, it is clear that the tested surfactants can be used in the manufacture of dyes, drugs, cosmetics, emulsifiers, pesticides, luminphores for optical applications and many other industries with low toxicity to human beings and the environment owing to their high solubility and good biodegradability.

1,4‐Dihydroxyanthraquinone and 1,8‐dihydroxyanthraquinone were alkylated with 3‐bromopropan‐1‐ol and subsequently transformed into the corresponding DMT protected phosphoramidite building blocks for insertion into loops of the G‐quadruplex of the thrombin binding aptamer (TBA). The 1,4‐disubstituted anthraquinone linker led to a significant stabilization of the G‐quadruplex structure upon replacing a T in each of two neighboring lateral TT loops and a 26.2° increase in thermal melting temperature was found. CD Spectra of the modified quadruplexes confirmed anti‐parallel conformations in all cases under potassium buffer conditions as previously observed for TBA. Although the majority of the anthraquinone modified TBA analogues showed a decrease in clotting times in a fibrinogen clotting assay when compared to TBA, modified aptamers containing a 1,8‐disubstituted anthraquinone linker replacing G8 or T9 in the TGT loop showed improved anticoagulant activities. Molecular modeling studies explained the increased thermal melting temperatures of anthraquinone‐modified G‐quadruplexes.

Reaction of stearic acid with semicarbazide in refluxing POCl3 afforded 2‐amino‐5‐heptadecyl 1,3,4‐oxadiazole. Acylation of the amino group with acetic anhydride, ethyl chloroacetate and chloroacetic acid gave amide and β‐amino acid derivatives. These compounds were cyclized to imidazo[2,1‐b]oxadiazole derivatives by two different techniques. Treating the starting oxadiazole compound with P2S5, hydroxyl amine and hydrazine hydrate in benzene afforded thiadiazole and triazole derivatives. Unexpectedly, triazolo[3,4‐b][1,3,4]oxadiazole derivative was obtained when 1,3,4‐oxadiazole derivative was refluxed with hydrazine hydrate in ethanol. The biological activities of the synthesized compounds were screened in vitro against some gram positive and gram negative bacteria and fungi. Addition of quantitative amount of propylene oxide units (3, 5, 7 mol) to the synthesized compounds afforded new nonionic surfactants. The physico‐chemical and surface properties of the novel synthesized surfactants such as surface and interfacial tension, cloud point, wetting time, emulsion stability, foam height, CMC, resistance to hydrolysis and their biodegradability were investigated. In addition, surface parameters including effectiveness (πCMC), efficiency (PC20), maximum surface excess (Γmax) and (Amin) were examined.

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