Abstract
Self-recognition and self-discrimination within complex mixtures are of fundamental importance in biological systems, which entirely rely on the preprogrammed monomer sequences and homochirality of biological macromolecules. Here we report artificial chirality- and sequence-selective successive self-sorting of chiral dimeric strands bearing carboxylic acid or amidine groups joined by chiral amide linkers with different sequences through homo- and complementary-duplex formations. A mixture of carboxylic acid dimers linked by racemic-1,2-cyclohexane bis-amides with different amide sequences (NHCO or CONH) self-associate to form homoduplexes in a completely sequence-selective way, the structures of which are different from each other depending on the linker amide sequences. The further addition of an enantiopure amide-linked amidine dimer to a mixture of the racemic carboxylic acid dimers resulted in the formation of a single optically pure complementary duplex with a 100% diastereoselectivity and complete sequence specificity stabilized by the amidinium–carboxylate salt bridges, leading to the perfect chirality- and sequence-selective duplex formation.
Highlights
Self-recognition and self-discrimination within complex mixtures are of fundamental importance in biological systems, which entirely rely on the preprogrammed monomer sequences and homochirality of biological macromolecules
During the course of our study, we found that an achiral carboxylic acid dimer joined by a pdiethynylbenzene linker with n-octyl (RA) substituents selfassociated into a racemic homodouble helix through interstrand hydrogen bonds between the carboxy groups (Fig. 1a, (CC2))[51]
We have found a complete sequence-selective chiral self-sorting in a mixture of racemic-1a and rac-2a mediated by unique interstrand multihydrogen-bond-driven homoduplex formations, the structures of which are significantly different from our expected self-associated homodouble helices, and are further different from each other depending on the linker amide sequences (NHCOcHex (L1) or CONH-cHex (L2), Fig. 1c)
Summary
Self-recognition and self-discrimination within complex mixtures are of fundamental importance in biological systems, which entirely rely on the preprogrammed monomer sequences and homochirality of biological macromolecules. High-fidelity self-recognition and self-discrimination are of principal importance in living systems[1], which enable biological macromolecules, such as proteins and DNA, to self-organize into uniform quaternary and double helical structures with a controlled handedness, respectively, through noncovalent interactions even within complex mixtures of subunits or molecular strands with a similar shape, size and sequence, thereby providing sophisticated functions that are essential for human life[1,2] Such an incredible self-sorting performance observed in biological systems relies on the preprogrammed monomer sequences and homochirality of their building blocks and components[2,3]. Hydrogen-bonddriven peptide nucleic acids[45] and metal-coordinate-bonded helicates[7,8,9,46] are known to show self-sorting with respect to their sequences and/or chain lengths, chirality- and sequenceselective successive self-sorting is currently unknown
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