Atsushi Narumi

Synthesis of amphiphilic triblock copolymer of polystyrene and poly(4-vinylbenzyl glucoside) via TEMPO-mediated living radical polymerization

Abstract 4-Vinylbenzyl glucoside peracetate 1 was polymerized with α,α′-bis(2′,2′,6′,6′-tetramethyl-1′-piperidinyloxy)-1,4-diethylbenzene 2 in chlorobenzene using (1 S )-(+)-10-camphorsulfonic acid anhydrous (CSA) as an accelerator ([ 1 ]=0.4xa0M,[ 1 ]/[ 2 ]/[CSA]=75/1/1.3) at 125xa0°C for 5xa0h. The polymerization afforded poly(4-vinylbenzyl glucoside peracetate) having TEMPO moieties on both sides of the chain ends, 3 , with a molecular weight ( M w,SLS ) of 8500, a polydispersity index ( M w / M n ) of 1.09, and an average degree of polymerization of the 1 unit ( x ) of 17. Styrene (St) was polymerized with 3 in chlorobenzene at 125xa0°C (St/chlorobenzene=1/2, w/w). The polymerization successfully afforded polystyrene–poly(4-vinyl glucoside peracetate)–polystyrene, 4 , when the polymerization time was below about 2xa0h. Polymer 4 with the M w,SLS of 12,500, 17,900, and 29,400, the compositions ( y – x – y ) of 20–17–20, 45–17–45, and 100–17–100, and the M w / M n of 1.12, 1.14 and 1.17 were modified by deacetylation using sodium methoxide in dry-THF into polystyrene–poly(4-vinyl glucoside peracetate)–polystyrene, 5 . The solubility of polymer 5 was examined using a good solvent for polystyrene such as toluene and for the saccharide such as H 2 O.

Lipase-catalyzed dynamic kinetic resolution of hemiaminals

The enzymatic dynamic kinetic resolution of N-acylhemiaminals by various lipases, namely, lipase PS, lipase AK and lipase QL, has been investigated. The acetylation of racemic N-acylhemiaminals with lipases exclusively produced the (R)-enantiomers in enantiomerically pure form and quantitative yields.

Synthesis of star‐shaped polystyrenes with glucose‐ and maltohexaose‐conjugated core through nitroxide‐controlled free‐radical polymerization

Coupling reactions of TEMPO-terminated polystyrene (PS-TEMPO) with divinylbenzene were performed in the presence of vinyl saccharides 1, successfully producing star-shaped polystyrenes with glycoconjugated core 2. Amphiphilic star-shaped polystyrenes with cores containing saccharide as hydrophilic segments 3 were obtained by the deacetylation of 2, which exhibited an encapsulation ability toward methyl orange (MO) in chloroform. A positive Cotton effect was observed in the CD spectrum for the MO/3 in the adsorption area of MO, indicating that MO existed in a chiral segment, i.e., the glycoconjugated core.

Chirality induction in cyclocopolymerization. 15. Enhancement of chirality induction during cyclocopolymerization of (2S,3S)-2,3-butanediyl bis(4-vinylbenzoate) with styrene using alkylaluminum compounds

The cyclocopolymerization of (2S,3S)-2,3-butanediyl bis(4-vinylbenzoate) (1) with styrene was carried out in dry toluene at 40°C in the presence of triethylaluminum (Et3Al), diethylaluminum chloride (Et2AlCl), and ethylaluminum dichloride (EtAlCl2), which played the role of Lewis acid capable of coordinating on carboxyl groups. After removal of the (2S,3S)-2,3-butanediyl units, the template-free polymer 3 exhibited an optical activity due to its main chain chirality. The specific rotations ([α]435, c 1.0, CHCl3) of polymers 3 prepared with alkylaluminum compound varied from −11.2 to −21.7°, which was higher than those prepared without alkylaluminum compound (−9.0°). The specific rotation of polymer 3 increased with an increase in the acidity of the alkylaluminum compounds (i.e. Et3Al<Et2AlCl<EtAlCl2) and/or with an increase in the molar ratio of alkylaluminum compound to monomer 1.