13. The Stereochemistry of Alanine Derivatives. 



By Charles Stanley Gibson and John Lionel Simonsen. 



The authors have for some considerable time been engag d 

 on the stereochemical study of compounds of the type : — 



CH 



s 



fi— C— NHR 



COOH 



where R is an acyl group, e.g., C^H fi . CO -(benzoyl), C«H 4 . 

 CH 8 . CO - (toluyl), C 8 H 4 . CH 3 . S0 2 - (sulphonyltolyl), etc. The 

 reason for choosing these compounds was because they were all 

 easily prepared, purified, and in most cases, beautifully crystal- 

 line : the latter being an important consideration since it is 

 hoped to make a crystallographic study of the racemic and 

 resolved compounds. The objects of the work are : — 



1. To investigate more completely the methods of the 

 resolution of externally compensated acids by naturally occur- 



ring optically active* bases and, where possible by synthetic 

 bases, in ways which have been more clearly indicated by Pope 

 and his co-workers and recently by the present authors, for th< 

 resolution of externally compensated bases. 



2. To determine the effect of slight changes in the con- 

 stitution of the group R, not directly united to the centre of 

 asymmetry in the compound, on the optical rotatory power and 

 ' lispersion", e.g., the effect of replacing the benzoyl by a toluyl 

 group, etc. Most of similar previous work has been concerned 

 with the effect of changing one or more groups directly attached 

 f o the centre of asymmetry. 



3. To determine the effect of the replacement of- CO by 

 ~S0 2 on the rotatory power. 



4. To determine quantitatively the influence of the same 

 change on the crystalline form of the racemic and optically 

 active compounds. 



In the case of externally compensated benzoyl alanine 

 p ope and ( Jibson have shown that different results are obtained 

 according as the compound is resolved by using brucine and 

 then strychnine, from when the bases are employed in the re- 

 v crse order: whereas Gibson and Simonsen have shown more 

 recent.lv that in the ease of externally compensated sulphonyl- 

 Molylalamne. the compound could easily be resolved by the 

 above two bases independently of the order in which they are 



