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Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives.

ABSTRACT: Bisureido- and a bisthioureido-substituted dibenzobarrelene derivative were synthesized and the photoreactivity of two representative examples were studied. Direct irradiation of the ureido-substituted derivative induces a di-?-methane rearrangement to the corresponding dibenzosemibullvalene derivative, whereas the thioureido-substituted derivative is almost photoinert. Complexes of the latter derivative with chloride, carboxylates, or sulfonate anions, however, are efficiently transformed to the dibenzosemibullvalene product upon irradiation, presumably by suppressing the self-quenching of the thiourea units in the complex. The association of the ureido-substituted dibenzobarrelene derivative with (S)-mandelate and irradiation of this complex led to the formation of the dibenzosemibullvalene with moderate stereoselectivity (68:32 er). In contrast, the thioureido derivative showed no such effect upon complexation of chiral anions.

SUBMITTER: Ihmels H

PROVIDER: S-EPMC3063053 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature

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Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives.

Ihmels Heiko H Luo Jia J

Beilstein journal of organic chemistry 20110304

Bisureido- and a bisthioureido-substituted dibenzobarrelene derivative were synthesized and the photoreactivity of two representative examples were studied. Direct irradiation of the ureido-substituted derivative induces a di-π-methane rearrangement to the corresponding dibenzosemibullvalene derivative, whereas the thioureido-substituted derivative is almost photoinert. Complexes of the latter derivative with chloride, carboxylates, or sulfonate anions, however, are efficiently transformed to th ...[more]

PMID: 21448249

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Project description:Supramolecular hydrogels have emerged as a class of promising biomaterials for applications such as drug delivery and tissue engineering. Self-assembling peptides have been well studied for such applications, but low molecular weight (LMW) amino acid-derived gelators have attracted interest as low-cost alternatives with similar emergent properties. Fluorenylmethyloxycarbonyl-phenylalanine (Fmoc-Phe) is one such privileged motif often chosen due to its inherent self-assembly potential. Previously, we developed cationic Fmoc-Phe-DAP gelators that assemble into hydrogel networks in aqueous NaCl solutions of sufficient ionic strength. The chloride anions in these solutions screen the cationic charge of the gelators to enable self-assembly to occur. Herein, we report the effects of varying the anions of sodium salts on the gelation potential, nanoscale morphology, and hydrogel viscoelastic properties of Fmoc-Phe-DAP and two of its fluorinated derivatives, Fmoc-3F-Phe-DAP and Fmoc-F5-Phe-DAP. It was observed that both the anion identity and gelator structure had a significant impact on the self-assembly and gelation properties of these derivatives. Changing the anion identity resulted in significant polymorphism of the nanoscale morphology of the assembled states that was dependent on the chemical structure of the gelator. The emergent viscoelastic character of the hydrogel networks was also found to be reliant on the anion identity and gelator structure. These results demonstrate the complex interplay between the gelator and environment that have a profound and often unpredictable impact on both self-assembly properties and emergent viscoelasticity in supramolecular hydrogels formed by LMW compounds. This work also illustrates the current lack of understanding that limits the rational design of potential biomaterials that will be in contact with complex biological fluids and provides motivation for additional research to correlate the chemical structure of LMW gelators with the structure and emergent properties of the resulting supramolecular assemblies as a function of environment.

Dataset Information

Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives.

Publications

Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives.

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