Phenylacetate methanolysis

The stereochemistry of each enantiomer separated by the chiral HPLC has been studied after methanolysis of the epoxy ring. Examining the H NMR data of esters of the produced methoxyalcohols with (S)- and (R)-a-methoxy-a-(tri-fluoromethyl) phenylacetic acid by a modified Mosher s method [181], it has been indicated that the earlier eluting parent epoxides are (3S,4R)-, (6S,7R)-, and (9R,10S)-isomers (Table 7) [75, 76, 179]. The above three chiral HPLC columns show different resolution abilities but a different elution order is not observed. The resolution profile by the reversed-phase OJ-R column has been generalized with molecular shapes of the epoxy compounds considering the... 

In a study by Berti et al., acid-catalyzed hydrolysis of styrene oxide was reported to occur with 67% inversion and 33% retention at the benzyl carbon.45 In a later study, it was reported that the styrene glycol product formed in the acid-catalyzed hydrolysis of chiral styrene oxide is completely racemic, which would indicate an A-l mechanism.46 As these two results indicate quite different mechanisms for this reaction, the glycol product from acid-catalyzed hydrolysis of chiral styrene oxide was converted to its bis-( + )-a-(methoxy-a-trifluoromethyl)phenylacetate diester derivative, and the composition of the diastereomeric diester mixture was determined by H NMR.47 This study agreed with those of Berti et al. and showed that acid-catalyzed hydrolysis of styrene oxide occurs with 67% inversion and 33% retention at the benzyl carbon. Acid-catalyzed methanolysis of styrene oxide is reported to occur with 89% inversion at the benzyl carbon.48 The fact that the diol product from acid-catalyzed hydrolysis of chiral styrene oxide is not completely racemic demonstrates that the lifetime of the carbocation is not sufficiently long for it to become symmetrically solvated. 

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