Absolute configuration of natural cyclohexene oxides by time dependent density functional theory calculation of the optical rotation: The absolute configuration of (-)-sphaeropsidone and (-)-episphaeropsidone revised
Absolute configuration of natural cyclohexene oxides by time dependent density functional theory calculation of the optical rotation: The absolute configuration of (-)-sphaeropsidone and (-)-episphaeropsidone revised
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DOI：
10.1021/jo070806i
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发表时间：
2007-08-31
影响因子：
3.6
通讯作者：
Rosini, Carlo
中科院分区：
文献类型：
--
作者：
Mennucci, Benedetta;Claps, Michele;Rosini, Carlo
本文报道了天然氧化环己烯的旋光能力，如（+）-查洛酮，1，（+）-表环氧甲吗啡，2，（+）-环氧甲吗啡，3，（+）-环氧酮，5，（-）-球葡萄糖苷酮，6，（-）-表葡萄糖苷酮，7和合成化合物（+）-表可可氧化物，4，用TDDFT/B3 LYP方法，在6- 31 G（d）和aug-cc-pVDZ基组上，采用极化连续模型，计算了气相和溶液中的C_2H_4 ~（3+）_2 ~（3+）_对于化合物1和2，具有高（约300个单位）的旋光度，气相计算与较小的基组能够再现的实验值的符号和数量级。相比之下，需要更大的基组来令人满意地模拟OR值3和4，其显示更小（约100个单位或更少）的旋转。对于不同的化合物，溶剂效应的纳入是不同的;对于1和2，它导致实验和预测之间更好的一致性，而对于3和4，氢键基团的存在使得连续溶剂化模型的应用不太令人满意。对于柔性系统5，使用气相计算和较小的基组不能确定绝对构型，但溶剂和较大基组效应的包含是强制性的。值得注意的是，如果采用文献中报道的AC进行理论预测，则在气相和溶剂中的计算都导致左旋天然化合物6和7的正旋光度。这有力地表明，以前在文献中分配给这些化合物的AC是不正确的，并且TDDFT预测OR值现已成为AC分配的实用工具。
The optical rotatory power of some natural cyclohexene oxides, such as (+)-chaloxone, 1, (+)-epiepoformine, 2, (+)-epoformine, 3, (+)-epoxidone, 5, (-)-sphaeropsidone, 6, (-)-episphaeropsidone, 7, and the synthetic compound (+)-epitheobroxide, 4, has been calculated by means of the TDDFT/B3LYP method using the 6-31G(d) and aug-cc-pVDZ basis sets, both in the gas phase and in solution by means of the polarizable continuum model. For compounds 1 and 2, which possess high (about 300 units) optical rotations, gas-phase calculations with the smaller basis set are able to reproduce the experimental values both in sign and order of magnitude. By contrast, a larger basis set is required to satisfactorily simulate the OR values of 3 and 4, which show smaller (about 100 units or less) rotations. The inclusion of the solvent effects is different for different compounds; for 1 and 2, it leads to a better agreement between experiment and prediction, while for 3 and 4, the presence of hydrogen bonding groups makes the application of continuum solvation models less satisfactory. For the flexible system 5, the absolute configuration could not be determined using gas-phase calculations and the smaller basis set, but both inclusion of solvent and larger basis set effects are compulsory. It is noteworthy that calculations both in the gas phase and in the solvent lead to a positive rotatory power for the laevorotatory natural compounds 6 and 7 if the ACs reported in the literature are employed to do the theoretical prediction. This strongly indicates that the ACs previously assigned to these compounds in the literature are not correct and that the TDDFT prediction of OR values has become by now a practicable tool for AC assignments.