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Stability of medium-bridged twisted amides in aqueous solutions.

ABSTRACT: "Twisted" amides containing nonstandard dihedral angles are typically hypersensitive to hydrolysis, a feature that has stringently limited their utility in water. We have synthesized a series of bridged lactams that contain a twisted amide linkage but exhibit enhanced stability in aqueous environments. Many of these compounds were extracted unchanged from aqueous mixtures ranging from the strongly basic to the strongly acidic. NMR experiments showed that tricyclic lactams undergo reversible hydrolysis at extreme pH ranges but that a number of compounds in this structure class are indefinitely stable under physiologically relevant pH conditions; one bicyclic example was additionally water-soluble. We examined the effect of structure on the reversibility of amide bond hydrolysis, which we attributed to the transannular nature of the amino acid analogs. These data suggest that medium-bridged lactams of these types should provide useful platforms for studying the behavior of twisted amides in aqueous systems.

SUBMITTER: Szostak M

PROVIDER: S-EPMC3281991 | biostudies-other | 2009 Mar

REPOSITORIES: biostudies-other

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Stability of medium-bridged twisted amides in aqueous solutions.

Szostak Michal M Yao Lei L Aubé Jeffrey J

The Journal of organic chemistry 20090301 5

"Twisted" amides containing nonstandard dihedral angles are typically hypersensitive to hydrolysis, a feature that has stringently limited their utility in water. We have synthesized a series of bridged lactams that contain a twisted amide linkage but exhibit enhanced stability in aqueous environments. Many of these compounds were extracted unchanged from aqueous mixtures ranging from the strongly basic to the strongly acidic. NMR experiments showed that tricyclic lactams undergo reversible hydr ...[more]

PMID: 19178141

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Project description:Deoxyribonucleic acid (DNA) carries the genetic information essential for the growth and functioning of living organisms, playing a significant role in life sciences research. However, the long-term storage and preservation of DNA, while ensuring its bioactivity, are still current challenges to overcome. In this work, aqueous solutions of ionic liquids (ILs) were investigated as potential preservation media for double stranded (dsDNA). A screening of several ILs, by combining the cholinium, tetrabutylammonium, tetrabutylphosphonium, and 1-ethyl-3-methylimidazolium, cations with the anions bromide, chloride, dihydrogen phosphate, acetate, and glycolate, was carried out in order to gather fundamental knowledge on the molecular features of ILs that improve the dsDNA stability. Different IL concentrations and the pH effect were also addressed. Circular dichroism (CD) spectroscopy was used to evaluate the conformational structure and stability of dsDNA. IL-DNA interactions were appraised by UV-Vis absorption spectrophotometry and 31P nuclear magnetic resonance (NMR) spectroscopy. The results obtained demonstrate that pH has a significant effect towards the dsDNA stability. Amongst the ILs investigated, cholinium-based ILs are the most promising class of ILs to preserve the dsDNA structure, in which electrostatic interactions between the cholinium cation and the DNA phosphate groups play a significant role as demonstrated by the 31P NMR data, being more relevant at higher IL concentrations. On the other hand, the denaturation of dsDNA mainly occurs with ILs composed of more hydrophobic cations and able to establish dispersive interactions with the nucleobases environment. Furthermore, the IL anion has a weaker impact when compared to the IL cation effect to interact with DNA molecules. The experimental data of this work provide relevant fundamental knowledge for the application of ILs in the preservation of nucleic acids, being of high relevance in the biotechnology field.

Dataset Information

Stability of medium-bridged twisted amides in aqueous solutions.

Publications

Stability of medium-bridged twisted amides in aqueous solutions.

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