With a Double Twist

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Science  24 Jun 2005:
Vol. 308, Issue 5730, pp. 1843
DOI: 10.1126/science.308.5730.1843a

The design of small-molecule oligomers that adopt conformations resembling the double-stranded helical structure of nucleic acids in solution has been challenging. Two strategies tried to date are to replace the phosphate ester backbone of nucleic acids with amides and to use metal ions to direct assembly of the strands.

Tanaka et al. describe how to build a double helix structure that relies on the formation of amidinium-carboxylate salt bridges to couple crescent-shaped backbones, which consist of m-terphenyl groups joined by a dialkyne linker. The right- or left-handedness of the double helices, which were characterized by circular dichroism and nuclear magnetic resonance of organic solutions and x-ray diffraction of crystals, is dictated by the chirality of the phenylethyl groups attached to the amidine. The presence of reactive trimethylsilylethynyl groups on the ends of these short strands should allow longer helices to be synthesized. — PDS

Angew. Chem. Int. Ed. 44, 3867 (2005).

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