186 A GENERAL REVIEW OF 



its value has been tested by many workers outside St. 

 Andrews. It is only possible to give a somewhat incomplete 

 summary of the applications of the reaction to the preparation 

 of different classes of substances, and at the same time to refer 

 to the more important problems which have been solved by 

 its aid. 



PBEPABATION OF SUBSTITUTED ACETIC ACIDS AND THEIR 



DERIVATIVES 



In the course of a research the chief object of which 

 was the determination of the optical effect of substituting 

 alkyl groups for alcoholic hydrogen in active mandelic acid, 

 McKenzie (3) prepared several phenylalkyloxy acetic acids. 

 By alkylating i-mandelic acid or its esters with the appropriate 

 alkyl iodide and silver oxide, he obtained products which 

 on hydrolysis yielded i-phenylisopropoxy-, i-phenylethoxy-, 

 and i-phenylmethoxy-acetic acids. Under similar conditions 

 Z-mandelic acid gave Z-phenylethoxyacetic acid, -phenyl- 

 methoxyacetic acid and its methyl ester, and Z-phenylisopro- 

 poxyacetic acid. When Z-mandelic acid was alkylated by 

 silver oxide and propyl iodide, an ester was obtained which 

 on hydrolysis yielded an inactive phenylpropoxyacetic acid. 

 Partial racemisation also occurred during one of the prepara- 

 tions of Z-phenylethoxyacetic acid. 



The racemic methoxy-, and propoxy-phenylacetic acids 

 prepared as above, together with a number of alkyloxysuccinic 

 acids, have been most usefully employed by McKenzie and 

 Harden (18) in an investigation on the biological method for 

 resolving inactive acids into their optically active components. 

 The results showed that the resolution is due to the mould 

 attacking one optical isomeride more readily than the other, 

 rather than to an attack by the organism on one isomeride 

 exclusively. No attempt was made, in this work, to isolate 

 a pure, active isomeride ; the detection of an optically active 



