For prochiral elements

With the development of the role for prochirality in biology, the need to demonstrate the existence of this phenomenon and to characterize it in precise structural terms became urgent. Along with such developments, chemists were interested in the study of compounds in which isotopic replacement led to chirality which could be expressed as optical activity. In other words, it was necessary to carry out determinations of the configurations of prochiral compounds. 

The possibility that optical activity could be demonstrated in a compound in which deuterium replaced hydrogen had long been considered by chemists. The first successful validations of this expectation were reported in 1949 the historical developments have been reviewed [10,11]. 

A large number of compounds has now been prepared in which chirality arises as a result of the presence of =CH2H or =CH3H. A few of them, which have been of particular importance, will be considered here to indicate some of the experimental strategies which have been used. More extensive general information is available [10,11], and Parry [86] has discussed chirally labeled a-amino acids. 

The correlation between glycolate, 72, and ethanol, 73, carried out in Arigoni s laboratory is of considerable importance (see [89] these results are also reported in [10]). 

The ethanol obtained by the reactions shown was characterized by its enzymatic behavior, rather than by optical properties. The acetaldehyde obtained on treatment with alcohol dehydrogenase retained 2H. Since the (— )-enantiomer of [2-2H]ethanol behaves in the same way, it follows that (S)-[2-2H]ethanol (absolute configuration defined by its derivation from (S )-[2-2 H]glycolate) is levorotatory. 

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