ON THE USE OF THE O-METHYLMANDELATE ESTER FOR ESTABLISHMENT OF ABSOLUTE-CONFIGURATION OF SECONDARY ALCOHOLS
ON THE USE OF THE O-METHYLMANDELATE ESTER FOR ESTABLISHMENT OF ABSOLUTE-CONFIGURATION OF SECONDARY ALCOHOLS
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DOI：
10.1021/jo00362a036
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发表时间：
1986-06-13
影响因子：
3.6
通讯作者：
SPRINGER, JP
中科院分区：
文献类型：
--
作者：
TROST, BM;BELLETIRE, JL;SPRINGER, JP
随着目前对获得对映体纯化合物的重视，拆分、测定对映体纯度和测定绝对溶质构型的方法变得很重要。在这三个方面都发挥作用的试剂是最理想的。Raban和Mislow2指出了o -甲基扁桃酸衍生物用于测定对映体纯度的效用。Dale和Mosher3更详细地研究了这种方法，特别是关于扁桃酸酯和a-（三氟甲基）-0-甲基扁桃酸酯。对于这两个，构象模型的发展是为了使不等价的感觉合理化。该模型为前一种酯选择了一种构象，在这种构象中，羟基由于氢键作用使酯的羰基黯然失色，而对于后一种酯，则选择了三氟甲基使羰基黯然失色的构象。虽然非对映异构体对之间的化学位移差异遵循了扁桃酸酯的变化趋势，但没有提出o -甲基扁桃酸酯的模型。这种经验方法很少用于绝对构型的赋值。此外，由于酯化过程中的外消旋化问题和缺乏分配绝对构型的模型，o -甲基曼德尔酸酯的使用较少。因为o -甲基扁桃酸酯似乎是解决所有三个目标的一种简便方法
With the current emphasis on obtaining enantiomerically pure compounds, methods for resolution, determination of enantiomeric purities, and determination of ab-solute configurations become important. 1 Reagents that function in all three regards are most desirable. Raban and Mislow2 pointed out the utility of O-methylmandelate derivatives for determination of enantiomeric purity. Dale and Mosher3 examined this approach in more detail-especially with respect to the mandelate esters and a-(tri-fluoromethyl)-0-methylmandelate esters. For these two, conformational models were developed to rationalize the sense of nonequivalence. The model chose a conformation for the former esters in which the OH group eclipses the carbonyl group of the ester due to hydrogen bonding and, for the latter esters, one in which the trifluoromethyl group eclipses the carbonyl group. No model was proposed for the O-methylmandelate although the trends in chemical shift differences between the diastereomeric pairs followed the mandelate esters. Little use of this empirical method for assignment of absolute configuration has been made. Furthermore, the O-methylmandelates have been less used because of the problems of racemization during esterification and the lack of a model for assignment of absolute configuration. Since O-methylmandelates appeared to represent a facile approach to all three goals for resolving