Cerchiaro Giselle, Sant'Ana Antonio Carlos, Temperini Marcia Laudelina Arruda, da Costa Ferreira Ana Maria
Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, PO Box 26077, São Paulo 05513-970, SP, Brazil.
Carbohydr Res. 2005 Oct 31;340(15):2352-9. doi: 10.1016/j.carres.2005.08.002.
With the aim of verifying different carbohydrate anomers coordinated to copper(II) ions, some copper(II) complexes with D-glucose (Glc), D-fructose (Fru), and D-galactose (Gal) were prepared and investigated by spectroscopic techniques. Their compositions were verified by elemental, ICP-AES and thermal analyses, in addition to conductivity measurements. The compounds isolated were consistent with the formula Na2[Cu2(carbohydrate)3].8H2O and Na[Cu2(carbohydrate)3].6H2O for the aldoses Glc and Gal, respectively, and Na2[Cu3(carbohydrate)4].8H2O in the case of the ketose, Fru. EPR spectra of these solids showed a rhombic environment around the metal center and suggested the presence of different anomers of the carbohydrates in each case. By Raman spectroscopy, it was possible to verify the predominance of the beta anomer of d-glucose in the corresponding copper complex, while in the free ligand the alpha anomer is predominant. In the case of the analogous complex with d-galactose, the spectrum of the complex shows bands of both anomers (alpha and beta) in approximately the same relative intensities as those observed in the isolated free ligand spectrum. On the other hand, for the complex with d-fructose a mixture of both furanose (five-membered ring) and pyranose (six-membered ring) structures was detected with prevalence of the furanose structure. Based on variations in the relative intensities of characteristic Raman bands, the binding site for copper in the fructose ligand was identified as most likely the 1-CH2OH and the anomeric 1-OH, while in beta-D-glucose it is presumably the anomeric 1-OH and the O-5 atom. These results indicated that EPR and Raman spectroscopy are suitable supporting techniques for the characterization of carbohydrate anomers coordinated to paramagnetic ions.
为了验证与铜（II）离子配位的不同碳水化合物异头物，制备了一些含有D-葡萄糖（Glc）、D-果糖（Fru）和D-半乳糖（Gal）的铜（II）配合物，并通过光谱技术进行了研究。除了电导率测量外，还通过元素分析、电感耦合等离子体原子发射光谱（ICP-AES）和热分析对它们的组成进行了验证。分离得到的化合物分别与醛糖Glc和Gal的化学式Na2[Cu2（碳水化合物）3]·8H2O和Na[Cu2（碳水化合物）3]·6H2O一致，而对于酮糖Fru，则为Na2[Cu3（碳水化合物）4]·8H2O。这些固体的电子顺磁共振（EPR）光谱显示金属中心周围存在菱形环境，并表明每种情况下碳水化合物都存在不同的异头物。通过拉曼光谱，可以验证相应铜配合物中D-葡萄糖的β异头物占主导地位，而在游离配体中α异头物占主导地位。在与D-半乳糖的类似配合物中，配合物的光谱显示两种异头物（α和β）的谱带，其相对强度与在分离的游离配体光谱中观察到的大致相同。另一方面，对于与D-果糖的配合物，检测到呋喃糖（五元环）和吡喃糖（六元环）结构的混合物，其中呋喃糖结构占优势。基于特征拉曼谱带相对强度的变化，果糖配体中铜的结合位点最有可能是1-CH2OH和异头1-OH，而在β-D-葡萄糖中，大概是异头1-OH和O-5原子。这些结果表明，EPR和拉曼光谱是表征与顺磁性离子配位的碳水化合物异头物的合适辅助技术。
