THE FOLIC ACID COMPLEX 



4. SYNTHESIS OF FOLIC ACID 

 Liver L. casei Factor 



Angier et al.,^ synthesised the liver L. casei factor (pteroylglutamic 

 acid) by four different methods. In the first/' ^ equimolecular amounts 

 of 2 : 4 : 5-triamino-6-hydroxypyrimidine, ^-aminobenzoyl-L-glutamic 

 acid and 2 : 3-dibromopropionaldehyde were reacted together in 

 presence of an acetate buffer : 

 N— C . OH 



C C . NH, Br . CH., 



II II -I- I + H2N<^ ^CO.NH.CH.CH^.CHa COOH 



N— C.NH2 Br.CH.CHO \==/ | 



COOH 



giving a product containing 15 % of the active compound. The 

 dihydro-compound was first formed and oxidised during the reaction 

 to the aromatic compound. The crude preparation was dissolved in 

 dilute alkali, impurities were precipitated by the addition of barium 

 chloride, followed by ethanol to a concentration of 20 % and the 

 solution was then freed from barium, adjusted to pU y-o, filtered and 

 extracted three times with lo-volume portions of butanol. The aque- 

 ous phase was concentrated, acidified to ^H 3-0 and cooled to 0-5° C. 

 The precipitate that formed was re-dissolved in dilute alkali, the solu- 

 tion treated with charcoal, acidified to pU 3-0 and the active compound 

 crystallised from hot water. The product was identical in its chemical 

 and physical properties with the L. casei factor isolated from liver. 



The second method of synthesis was slightly different. i' ^ 2:3- 

 Dibromo-propionaldehyde was reacted with pyridine, and the product 

 was condensed with 2:4: 5-triamino-6-hydroxy-pyrimidine and 

 potassium iodide to give N-[(2-amino-4-hydroxy-6-pteridyl)-methyl]- 

 pyridinium iodide. This was then condensed with ^-aminobenzoyl-L- 

 glutamic acid by heating with sodium methoxide in ethylene glycol 

 at 140° C. The product again contained 15 % of the active compound 

 and was piuified as described above. 



Pteroic acid was synthesised by both the above methods, using 

 ^-aminobenzoic acid in place of ^-aminobenzoyl-L-glutamic acid.^' ^' ^ 



A third method of synthesis * was to treat reductone (2 : 3-dihy- 

 droxyacrylaldehyde) with ^-aminobenzoyl glutamic acid, esterify the 

 resulting p-(2 : 3-dihydroxy-2-ene-propylideneamino)-benzoylglutamic 

 acid and condense the ester with 2:4: 5-triamino-6-hydroxy- 

 pyrimidine : — 

 N=C . OH 



H2N . C C . NH2 CHOH ^ ^ 



II 11+11 + H^N^ >CO . NH . CH . CH2 . CH2 . COOH 



N— C . NH2 C(OH) . CHO \==--/ I 



474 



COOH 



