Absolute configuration enantiopure MaNP acid

Various fluorinated diphenylmethanols 36-39 were also enantioresolved as CSDP esters (entries 23-26). In the case of alcohols 36, 37, and 39, their absolute configurations were determined by X-ray crystallography. To those fluorinated alcohols, the method of MaNP acid 3 could be applied for enantioresolution and also for determination of their absolute configurations by the H NMR anisotropy method, as discussed below. Meto-substituted diphenylmethanols 40 and 41 were enantioresolved by the CSDP acid method yielding enantiopure alcohols, the abso-... 

The MaNP acid method has been successfully applied to various racemic alcohols listed in Table 9.3 for preparation of enantiopure secondary alcohols and the simultaneous determination of their absolute configurations. If the separation factor a is as large as in the case of l-octyn-3-ol 56 (entry 2 in Table 9.3, a. = 1.88), a large-scale HPLC separation of diastereomeric MaNP esters is feasible. For example, in the case of esters 64a and 64b derived from alcohol 56, ca. 0.85-1.0 g of the mixture was separable in one run by the HPLC (hexane/EtOAc = 20 1) using a silica gel glass column (22 x 300 mm) (Figs. 9.19 and 9.20). 

The same MaNP method was next applied to enantiopure alcohol +)-77, which was obtained by the CSDP acid method. Its absolute configuration, however, had remained undetermined, because its CSDP esters did not crystallize as ideal single crystals suitable for X-ray analysis. To determine the absolute configuration of (+)-77, it was subjected to the esterification with MaNP acids yielding (R,X)-78 and (,S,X)-78 (Fig. 9.22). The Ad values were similarly calculated as shown in... 

As described above, the methods of CSDP acid and MaNP acid are very powerful for the preparation of enantiopure alcohols and also for simultaneous determination of their absolute configurations. If single crystals of CSDP esters are not available, the NMR anisotropy method using MaNP acid is powerful as the complementary tool. 

Kasai Y, Taji H, Fujita T, Yamamoto Y, Akagi M, Sugio A, Kuwahara S, Watanabe M, Harada N, Ichikawa A, Schurig V. MaNP acid, a powerful chiral molecular tool for preparation of enantiopure alcohols by resolution and determination of their absolute configurations by the H NMR anisotropy method. Chirality 2004 16 569-585. 

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