No abstract

Coulombic complexes of amphiphilic polyanions and double-chain cationic surfactants were prepared by adding an aqueous solution of didodecyldimethylammonium bromide (DDAB) to aqueous solutions of terpolymers consisting of sodium 2-(acrylamido)-2-methylpropanesulfonate, 7V-(l-adamantyl)methacryIamide (49 mol %) or N-(l-naphthylmethyl)methacrylamide (59 mol %), and JV-(l-pyrenylmethyl)methacrylamide (1 mol %). As the contents of the adamantyl and naphthyl groups in the terpolymers are sufficiently high, the parent terpolymers adopt micellelike microphase structures in aqueous solution. Both the complexes of the adamantyl and naphthyl terpolymers with DDAB were soluble in benzene, methanol, tetrahydrofuran (THF), acetonitrile (ACN), IV^V-dimethylformamide (DMF), etc.NMR spectra indicated that the quantitative numbers of DDAB were ionically bound to the sulfonate sites in the parent terpolymers. Dynamic light scattering data for the complex of the adamantyl terpolymer showed that the size of the complex in THF solution ranged from 6 to 15 nm in diameter, which fairly agreed with a radius of gyration estimated on the basis of GPC data.NMR spectra, 2D-NOESY, and spin-lattice and spin-spin relaxation times for the complex of the naphthyl terpolymer in organic solution revealed that the motions of the naphthyl residues were highly restricted, while those of the DDAB residues were much less restricted. These findings imply that the micellelike microphase structure of the parent amphiphilic polyanions formed in aqueous solution remained rather intact in the complexes even though they were dissolved in organic solvents. In benzene solution, the complex was shown to be in a particularly compact form. Fluorescence emitted by the pyrenyl probes incorporated in the complexes supported these findings.

A molecular composite of an amphiphilic polyanion and cationic surfactants was prepared by treating a terpolymer [consisting of sodium 2‐acrylamido‐2‐methylpropanesulfonate, N‐(1‐adamantyl)methacrylamide, and a small mole fraction of N‐(1‐pyrenylmethyl)methacrylamide] with didodocyldimethylammonium bromide in aqueous solution. The molecular composite was soluble in organic solvents with a wide range of polarities. Fluorescence spectra indicated that the pyrenyl (Py) residues in the molecular composite experienced polar microenvironments even though the composite was dissolved in nonpolar solvents. Exciplex formation of the Py residue with 4,4′‐dicyanobenzene was strongly suppressed due to the polar microenvironments and steric “protection” of the chromophore. Photoinduced electron transfer (ET) from the Py residue to pyromellitic dianhydride (PMDA) in acetonitrile showed characteristics of long‐range ET between fixed donor and acceptor sites and yielded long‐lived transient Py cation radicals and PMDA anion radicals which persisted for tens of milliseconds. These findings imply that the micellelike structure of the parent amphiphilic polyelectrolyte formed in aqueous solution is retained, to some degree, in the molecular composite dissolved in organic solvents. © 1992 John Wiley & Sons, Inc.

Amphiphilic terpolymers [consisting of 50 mol % of sodium sulfonate groups, 49.5 mol % of lauryl (La) or cyclododecyl (Cd) groups, and 0.5 mol % of a moiety of azobenzene substituted with a La group (Abz-La) or with a Cd group (Abz-Cd)] were prepared. Reference copolymers [consisting of 99.5 mol % of sodium sulfonate groups and 0.5 mol % of the Abz-La or Abz-Cd residue] were also prepared. In the terpolymers, the Abz-La and Abz-Cd residues were incorporated in the self-organized hydrophobic phases in aqueous solution, while in the reference copolymers, they are exposed to the aqueous phase. The mobility of the hydrophobic groups and azobenzene moieties in the co-and terpolymers in DzO was estimated by -NMR relaxation techniques. Spin-lattice and spin-spin relaxation times indicated that the motions of the azobenzene moieties in the terpolymers were highly restricted owing to the self-organization of the hydrophobic groups in aqueous solution. In particular, the hydrophobic self-organization of the Cd groups caused more pronounced restrictions on the motions of the azobenzene moieties than the La groups did. Effects of such motional restrictions on the trans-to-cis photoisomerization and cis-to-trans thermal back-isomerization of the azobenzene moieties were investigated, finding that the former was considerably impeded, while the latter was accelerated. As predicted by the NMR relaxation times, these effects on the isomerizations were more pronounced with the Cd groups than with the La groups; i.e., motional restrictions imposed on the trans isomer and residual strains in the photogenerated cis isomer are larger in the organized Cd phase than in the La phase. These findings indicate that the Cd groups are more densely packed than are the La groups in the self-organized hydrophobic phases presumably because the Cd residue has much less conformational freedoms than does the La residue.

Synthesis of diarylmethanes, a key building block for SGLT2 inhibitors, has been developed through ketone synthesis by Friedel–Crafts acylation with TiCl4, followed by reduction with TiCl4/NaBH4. The new protocol proceeded more cleanly than the previous methods employing AlCl3 and BF3·OEt2/Et3SiH to provide the diarylmethanes corresponding to canagliflozin, empagliflozin, and luseogliflozin in a highly expedient and affordable manner. In the case of a diarylmethane for the synthesis of dapagliflozin, the reduction step took place by an alternative method using InCl3/Al/BF3·OEt2.