RESUMO
Two novel dendritic macromonomers 7 and 8 functionalized with electroactive conjugated thiophene oligomers were synthesized by stepwise cross-coupling reactions and the introduction of a vinyl group at the focal point. Both macromonomers were polymerized into dendronized polymers 9 and 10 by using a radical polymerization method. The photophysical and redox behaviors of dendronized polymers 9 and 10 are significantly different from those of the corresponding macromonomers. This difference may result from the spatial overlapping of thiophene dendrons through π-π interactions when the dendrons are connected to a polymer backbone. The dendronized polymers can organize into large-area two-dimensional sheets with a thickness of 4.8â nm. Polymer 9, which has all-dendritic thiophene side chains, exhibited enhanced conductivity by partial doping with iodine or nitrosonium tetrafluoroborate (NOBF(4)). The novel amphiphilic dendronized polymer 15 was synthesized by the atom-transfer radical polymerization of macromonomer 7 from a poly(ethylene glycol) (PEG) macroinitiator and was found to have a self-organized structure in water.
RESUMO
Racemization of the C-terminal amino acid (Ala) has been studied in various solvents during coupling between 4-methoxybenzyloxycarbonyl (Z(OMe))-Gly-L-Ala-OH and phenylalanine benzyl ester (H-Phe-OBzl) with 4-(4,6-dimethoxy-1,3,5-thiazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). The reaction occurred without substantial racemization in AcOEt, tetrahydrofuran (THF), N,N-dimethylformamide (DMF), CH3CN, and 2-PrOH, while a slight racemization was observed in dimethyl sulfoxide (DMSO), EtOH, and MeOH. The extent of racemization may correlate with the polarity of the solvents.
