Chirality- and sequence-selective successive self-sorting via specific homo- and complementary-duplex formations

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.

Complementary double‐stranded helical oligomers bearing achiral bifunctional groups that catalyze asymmetric aldol reaction

“…The opticallyactive single strands ( R )‐ 1 and ( R )‐ 3 showed very weak CD signals in the same absorption regions as anticipated (Figure A,B). These results suggest that the chirality of the amidine units is efficiently transferred to the next achiral piperazine unit when complexed with the complementary achiral carboxylic acid strands, resulting in an excess of the right‐handed double helices induced by the chiral amidine residues with an ( R )‐configuration . The helix‐sense excesses of the ( R )‐ 1 · 2 and ( R )‐ 3 · 4 double helices could not be exactly estimated because their CD spectral patterns and intensities were different from those of the completely right‐handed double‐helical ( R )‐ AA · CC complex, but that of the ( R )‐ 1 · 2 duplex was, at least, likely imperfect at 25°C.…”

“…Here, we show the invaluable role of a complementary double‐helical framework with a controlled helicity for supramolecular bifunctional asymmetric organocatalysis. The design and synthesis of complementary double‐helical bifunctional organocatalysts is based on our modular strategy using m ‐terphenyl‐based complementary double helices stabilized by chiral amidinium–achiral carboxylate salt bridges . We anticipated that even catalytically active achiral functional amino residues could be introduced at the terminus (edge‐achiral dimer: ( R )‐ 1 ) or center (center‐achiral trimer: ( R )‐ 3 ) of the chiral strands while maintaining the one‐handed double‐helical structures assisted by the chiral amidine residues once complexed with the corresponding achiral complementary carboxylic acid strands .…”

“…The design and synthesis of complementary double‐helical bifunctional organocatalysts is based on our modular strategy using m ‐terphenyl‐based complementary double helices stabilized by chiral amidinium–achiral carboxylate salt bridges . We anticipated that even catalytically active achiral functional amino residues could be introduced at the terminus (edge‐achiral dimer: ( R )‐ 1 ) or center (center‐achiral trimer: ( R )‐ 3 ) of the chiral strands while maintaining the one‐handed double‐helical structures assisted by the chiral amidine residues once complexed with the corresponding achiral complementary carboxylic acid strands . The resulting supramolecular bifunctional double‐helical organocatalysts would catalyze the asymmetric direct aldol reaction because of its doubly helical chirality and cooperative effect of the two functional amino and carboxy groups arranging in close proximity to one another in a chiral fashion through a complementary one‐handed double‐helix formation (Figure ).…”

“…The design and synthesis of complementary double-helical bifunctional organocatalysts is based on our modular strategy using m-terphenyl-based complementary double helices stabilized by chiral amidiniumachiral carboxylate salt bridges. 12,15,[19][20][21][22][23][24] We anticipated that even catalytically active achiral functional amino residues could be introduced at the terminus (edge-achiral dimer: (R)-1) or center (center-achiral trimer: (R)-3) of [This article is part of the Special Issue: In honor and memory of Prof. Koji Nakanishi. See the first articles for this special issue previously published in Volumes 31:12.…”

A Kinetic Self‐Sorting Approach to Heterocircuit [3]Rotaxanes

“…However,t his raises the synthetic complexity of the thread, and only limited, stereochemically trivial examples have been reported. [8] Self-sorting,i nw hich multiple components selectively assemble themselves into complex architectures, [9] is aparticularly successful and attractive approach for the synthesis of complex supramolecular systems [10][11][12] and materials. [8] Self-sorting,i nw hich multiple components selectively assemble themselves into complex architectures, [9] is aparticularly successful and attractive approach for the synthesis of complex supramolecular systems [10][11][12] and materials.…”