II. CHEMISTRY 109 



E. SPECIFICITY 



1. Chemistry of Rhizopterin (Formyl Pteroic Acid) 



Keresztesy et al.^''- ^^ reported the isolation of a compound wliich was 

 highly active for S. faecalis but relatively inactive for L. casei. This ratio of 

 activity for these two organisms is in contrast to that of pteroyltriglutamic 

 acid which is more active for L. casei than for S. faecalis. Rhizopterin was 

 obtained from a charcoal adsorbate derived from a fumaric acid fermenta- 

 tion product of Rhizopiis nigricans. It was isolated by adsorption on Norit 

 and fuller's earth and by chromatographic adsorption on alumina. 



Wolf et al.^^ described a novel method for recrystallizing rhizopterin by 

 forming a double salt ^\^th luteoethylenediamine cobaltic chloride. This 

 double salt was recrystallized from hot water and reconverted back to 

 rhizopterin by treatment with acetic acid. 



Alkaline treatment of rhizopterin was shown hy Rickcs et al.^^ to decrease 

 its activity for S. faecalis, to have no effect on its L. casei activity, and to 

 change the adsorption spectrum. This alkaline degradation product was 

 shown by Wolf et al.^° to be pteroic acid. Acid hydrolysis of rhizopterin 

 yielded formic acid. The position of the formyl group on the N'" position 

 of the p-aminobenzoic acid was established by the following reactions. 

 Benzoylrhizopterin was prepared which yielded benzoylguanidine on oxida- 

 tion with potassium chlorate and hydrochloric acid. This showed that the 

 2-amino group of rhizopterin was free and that benzoylation occurred on 

 this nitrogen atom. Oxidation of rhizopterin ^^^th potassium chlorate and 

 hydrochloric acid yielded tetrachloro-p-benzoquinone, an oxidation product 

 of p-aminobenzoic acid and oxaloguanidine which in turn yielded guanidine 

 on acid hydrolysis. p-Aminobenzoic acid was obtained by sublimation of 

 the alkahne hydrolysis product (pteroic acid) at 220 to 360° at very low 

 pressure and by acid or alkaline hydrolysis. A number of different acyl 

 derivatives were prepared by heating rhizopterin with the corresponding 

 acid anhydrides. These acyl groups were attached to the 2-amino group. 

 The 2-amino group could be removed by nitrous acid to give desimino- 

 rhizopterin. 



Rhizopterin was synthesized by treatment of synthetic pteroic acid, ob- 

 tained by the method of Waller," with 98% formic acid on a steam bath 



" J. C. Keresztesy, E. L. Rickes, and J. L. Stokes, Science 97, 465 (1943). 

 68 E. L. Rickes, L. Chaiet, and J. C. Keresztesy, J. Am. Chetn. Soc. 69, 2749 (1947). 

 *8 E. L. Rickes, X. R. Trenner, J. B. Conn, and J. C. Keresztesy, J. Am. Chem. Soc. 

 69, 2751 (1947). 



