Trans and Cis Effects of Axial Fluoroalkyl Ligands in Vitamin B12 Analogues: Relationship between Alkyl- and Fluoroalkyl-Cobalamins

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• 作者：Lucio Randaccio ; Giovanna Brancatelli ; Nicola Demitri ; Renata Dreos ; Neal Hickey ; Patrizia Siega ; Silvano Geremia
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：December 2, 2013
• 年：2013
• 卷：52
• 期：23
• 页码：13392-13401
• 全文大小：502K
• 年卷期：v.52,no.23(December 2, 2013)
• ISSN：1520-510X

文摘

CF₂HCbl, CF₃Cbl , and CF₃CH₂Cbl have been synthesized and characterized in solution by ¹H NMR and UV鈥搗is spectroscopy, and their X-ray crystal structures have been determined using synchrotron radiation. The structure of CF₃CH₂Cbl is reported for the first time, whereas those of CF₂HCbl and CF₃Cbl are re-examined to obtain more precise structural data. Comparison of the structural data obtained with the alkylcobalamin analogues, MeCbl and EtCbl, indicates that the Co鈥揅 and Co鈥揘B3 bond lengths are shorter in the fluoroalkylcobalamins. The structural data of the fluoroalkylcobalamins previously reported in the literature had been conflicting in this regard. Thus, a much less dramatic shortening of the two axial bonds was found for CF₃Cbl, whereas in the case of CF₂HCbl, the Co鈥揘B3 bond length is shorter than in MeCbl. Direct comparison of the structures of CF₃CH₂Cbl and EtCbl indicates a large distortion of the axial fragment in the former case that can be attributed to steric effects. A number of previously reported correlations of the effect of the 尾-ligand on the structure and properties of cobalamins are re-examined in light of the present results. Particular emphasis is placed on the axial fragment. This analysis substantially confirms and, with the new data reported here, adjusts and expands the data set for correlations between trans and cis influences of the 尾-ligand of cobalamins and their structure (Co鈥揦 and Co鈥揘B3 distances and corrin fold angle) and properties (UV鈥搗is spectra, NMR spectra, and pK_base-off).