no SCIENCE PROGRESS 



this method, e.g. leucylalanine, alanylleucine, alanylleucyl- 

 glycine, leucylalanylglycine, glycylalanylleucine, etc. 



Fischer has ultimately been able to prepare the acid chloride 

 of the amino acid so that it can be used directly for synthesis. 

 Whereas the acid chlorides of the halogenacyl derivatives were 

 easily prepared by the action of phosphorus chloride, this 

 did not take place with hippuric acid. After many attempts 

 to prepare hippuryl chloride, success at length was attained 

 when hippuric acid was heated with acetylchloride and phos- 

 phorus pentachloride together. By simply extending this method 

 of preparation to the amino acids themselves, i.e. by shaking 

 them in a finely powdered condition with acetylchloride and 

 phosphorus pentachloride, Fischer obtained the acid chlorides 

 of the amino acids, whereby a step in the synthetical processes 

 can be saved. 



During the course of the last year several higher poly- 

 peptides have been synthesised by these methods ; these are 

 two hexapeptides, a heptapeptide, an octapeptide, and even a 

 dodekapeptide. They all consist principally of glycine residues, 

 the dodekapeptide having one leucine and eleven glycine 

 radicles. Such long glycine chains probably do not exist in 

 the protein molecule, except possibly in gelatine, which contains 

 about 20 per cent, glycine. Their study, however, is of great 

 importance in that they cannot exist in stereoisomeric forms, 

 and the knowledge of their properties may lead to the isolation 

 of a higher polypeptide from the proteins themselves. Further, 

 the material is of easy access, glycine being readily prepared 

 synthetically, which is not the case with the other amino acids, 

 many of which are more easily obtained by the hydrolysis of 

 proteins than by synthesis. 



In a quite recent paper Fischer gives an account of the prepara- 

 tion of an octadecapeptide, built up of fifteen glycine and three 

 1-leucine residues, i.e. a polypeptide containing six more members 

 in its molecule than the above-mentioned dodekapeptide. Its 

 preparation is of great interest, as it shows very clearly how the 

 synthetical method has been employed in these researches. 

 Pentaglycylglycine and d-a-bromisocapronyldiglycylglycine, 

 BrCH(C 4 H 9 )CO.[NHCH,CO],.NHCH 2 COOH are used. The 

 acid chloride of the latter compound is first prepared and 

 combined with the hexapeptide. The bromo compound so 

 obtained on treatment with liquid ammonia gives 1-leucyl- 



