Akihiro Yokoyama

Chiral amplification based on sergeants and soldier effect in helically folded poly(naphthalenecarboxamide) was reported. Copolymerization of chiral monomer and achiral monomer was carried out in the presence of phenyl 4-methylbenzoate as an initiator and lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) as a base under several conditions. The copolymer obtained as the polymerization progressed was followed by GPC, and the chiral monomer unit ratio was estimated from the 1H NMR spectrum after purification of the products by HPLC. The ratios of the chiral monomer unit to the achiral monomer unit in the products remained almost constant during the polymerization, indicating that random copolymerization proceeded. The results show that strong cooperativity between the monomer units composing the helical structure would arise from the intramolecular self-association of the main chain of the poly(naphthalenecarboxide), driven by the solvophobic effect in the aqueous solvent system.

The synthesis of poly (naphthalenecarboxamide) with a chiral tri (ethylene glycol) side chain and their secondary structure in solution was discussed. The helical structure was confirmed by X- ray crystallographic analysis of oligo (N-methyl-p-benzamide), which revealed a helical conformation with three monomer units per turn in crystal and by exciton model analysis of CD spectra induced by the secondary structure of the polyamide. The UV and CD spectra in solution indicated that the polyamide adopts a one-handed helical conformation. The excitation model analysis of the UV and CD spectra indicated that poly (naphthalenecarboxamide) with a chiral tri (ethylene glycol) side chain has adopted a thermodynamically controlled right handed helical conformation in organic solvents. The folding of napthalene polyamide can be enhanced by a solvophobic effect and completed at 0-15 ° C in 70% water-methanol.