Summary: A series of novel, thermo‐sensitive copolymers with different molar ratios of N‐isopropylacrylamide (NIPAM) and hydrophobic cis‐dibenzo‐18‐crown‐6‐diacrylamide (cis‐DBCAm) were prepared via free‐radical copolymerization. cis‐DBCAm with polymerizable end groups was successfully synthesized by reacting the corresponding amino crown ether with acryloyl chloride. The copolymers were characterized by FT‐IR and elemental analysis, and the thermo‐sensitivities of the copolymers were evaluated by measuring their lower critical solution temperatures (LCSTs) in the absence or presence of various metal ions. The results indicated that incorporation of cis‐DBCAm lowered LCSTs, and that the LCSTs of the copolymers decreased with the increase in cis‐DBCAm content in the copolymers. When the cavities of the crown ether units captured either K+ or Cs+ ions, the LCST of the respective copolymer–metal ion complex was further decreased, whereas the capture of Na+ or Li+ ions did not have a significant influence on the LCSTs of the copolymers.
Incorporation of cis‐DBCAm into PNIPAM resulted in a lower LCST. The LCST was decreased more when the cavities of the crown ether units captured K+ ions. 相似文献
A new amide, N‐cis‐sinapoyltyramine ( 1 ), and twelve known compounds were isolated from the aerial parts of Lindera glauca. The structure of the new compound has been established by the study of extensive 2D NMR data. 相似文献
Benzyl 2,4,6-tri-O-benzyl-β-D-galactopyranoside (6) was synthesised from regioselective protection of stannylated benzyl 2,6-di-O-benzyl -β-D-galactopyranoside (3) with 4-methoxybenzyl chloride, followed by benzylation and oxidative removal of the temporary protecting group. The disaccharide (2) was prepared by condensation of the common acceptor 6 with 7 through thial activation as well as with 8 following Konigs Knorr procedure. 相似文献
The conformational study on N-methoxycarbonyl-L-proline-N'-methylamide (Moc-Pro-NHMe, prolylcarbamate) is carried out using ab initio HF and density functional B3LYP methods with the self-consistent reaction field method in the gas phase and in solution (chloroform, acetonitrile, and water). The replacement of the N-acetyl group by the N-methoxycarbonyl group results in the changes in conformational preferences, populations for backbone and prolyl puckering, and barriers to cis-trans isomerization of the prolyl residue in the gas phase and in solution, although there are small changes in the geometry of the prolyl peptide bond and the torsion angles of backbone and prolyl ring. The cis population increases with the increase of solvent polarity, as found for Ac-Pro-NHMe (prolylamide), but it is amplified by 9% in the gas phase and about 17% in solution for prolylcarbamate compared with those for prolylamide. It is found that the cis-trans isomerization for prolylcarbamate proceeds through the clockwise rotation with omega' approximately +120 degrees about the prolyl peptide bond in the gas phase and in solution, as found for prolylamide. However, the rotational barriers to the cis-trans isomerization for prolylcarbamate are calculated to be 3.7-4.7 kcal/mol lower than those of prolylamide in the gas phase and in solution, and are found to be less sensitive to the solvent polarity. The calculated rotational barriers for prolylcarbamate in chloroform and water are in good agreement with the observed values. The shorter hydrogen-bond distance between the prolyl nitrogen and the amide H (H(NHMe)) of the NHMe group, the decrease in electron overlap of the prolyl C-N bond, and the favorable electrostatic interaction between the ester oxygen and the amide H(NHMe) for the transition state seem to play a role in lowering the rotational barrier of prolylcarbamate. The smaller molecular dipole moments of the ground- and transition-state structures for prolylcarbamate in the gas phase and in solution seem to be one of factors to make the rotational barrier less sensitive to the solvent polarity. As the solvent polarity increases (i.e., from the gas phase to chloroform to acetonitrile), the value of DeltaH(tc)(double dagger) decreases and the magnitude of DeltaS(tc)(double dagger) increases for prolylcarbamate, which results in a nearly constant value of the rotational barrier. 相似文献
The crystal structures of cis‐dichlorido(ethylamine‐κN)(piperidine‐κN)platinum(II), [PtCl2(C2H7N)(C5H11N)], (I), cis‐dichlorido(3‐methoxyaniline‐κN)(piperidine‐κN)platinum(II), [PtCl2(C5H11N)(C7H9NO)], (II), and cis‐dichlorido(piperidine‐κN)(quinoline‐κN)platinum(II), [PtCl2(C5H11N)(C9H7N)], (III), have been determined at 100 K in order to verify the influence of the nonpiperidine ligand on the geometry and crystal packing. The crystal packing is characterized by N—H...Cl hydrogen bonding, resulting in the formation of chains of molecules connected in a head‐to‐tail fashion. Hydrogen‐bonding interactions play a major role in the packing of (I), where the chains further aggregate into planes, but less so in the case of (II) and (III), where π–π stacking interactions are of greater importance. 相似文献
Benzylation in the α,α′‐positions in the benzospirane, 2,2′‐spirobiindane in a cis,cis manner has been effected from the corresponding diketone. Initial Grignard reactions and subsequent water elimination provided a stereoisomeric mixture of α,α′‐alkylidene intermediates, which were stereoselectively hydrogenated to cis,cis‐dibenzyl derivatives. The structure of intermediates in the reaction sequence has been ascertained by X‐ray analyses. 相似文献