Abstract
A new series of bisteroidal esters was synthesized using a spacer group, sterols and sapogenins as substrates. Steroidal dimers were prepared in high yields employing diesters of terephthalic acid as linkages at the 3β, 3′β steroidal positions. In all attempts to crystallize bisteroids, it was observed that the compounds tended to self-organize in solution, which was detected when employing various solvent systems. The non-covalent interactions (van der Waals) of the steroidal moieties of this series of symmetrical bisteroids, the polarity of the solvents systems, and the different solubilities of the bisteroid aggregates, indeed induce the molecules to self-assemble into supramolecular structures with well-defined organization. Our results show that the self-assembled structures for the bisteroidal derivatives depend on the solvent system used: with hexane/EtOAc, membrane-shaped structures were obtained, while pure EtOAc afforded strand-shaped arrangements. In the CHCl3/CH3OH system, thin strands were formed, since van der Waals interactions are lowered in this system, as a consequence of the increased solubility of the bisteroids in CHCl3. Based on the characterization by SEM and XRD, we show evidence that the phenomenon of self-assembly of bisteroids occurs presenting different morphologies depending on the solvent used. The new steroidal dimer derivatives were characterized by NMR, TGA, DSC, SEM, and XRD. Finally, the molecular structure of one bisteroid was confirmed by single-crystal X-ray analysis.
Highlights
IntroductionSteroid dimers belong to an essential group of pharmacologically active compounds that are predominantly biosynthesized by marine organisms [2,3]
In the chemistry of steroids, there is a constant interest in performing structural modifications on steroids to optimize their biological and pharmacological activities or to search new properties.Steroid dimers are a particular group that are well known for their rigid, predictable, and inherently asymmetric architecture [1].Steroid dimers belong to an essential group of pharmacologically active compounds that are predominantly biosynthesized by marine organisms [2,3]
The self-organized behaviour is triggered by solvents, that leads to a non-permeable non-porous layer dimer in contact with the hexane/EtOAc system (25:1); as well as the formation of aggregates in the form of strands of the bisteroidal compounds was observed in contact with pure
Summary
Steroid dimers belong to an essential group of pharmacologically active compounds that are predominantly biosynthesized by marine organisms [2,3]. Bisteroidal conjugates caught caught great great attention attention in in the the last last years years due due to to their their noteworthy noteworthy applications applications in in biology, biology, conjugates medicine, and supramolecular chemistry [5]. Examples of naturally occurring bisteroids are ritterazines medicine, and supramolecular chemistry [5]. Examples of naturally occurring bisteroids are and cephalostatins [6,7], which are marine natural productsnatural containing either containing two spirostanic or two two ritterazines and cephalostatins [6,7], which are marine products either spirodifuranic units connected byunits a pyrazine ring by
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