SOLUBLE, NITROGENOUS CONSTITUENTS OF PLANTS Sy 
which may be metabolized. The analogy thus disclosed between lysine and pipecolic 
acid, with glutamic acid and proline, now finds an unexpected but possible parallel in 
the compounds with four carbon atoms, as suggested by the unexpected new com- 
pound azetidine-2-carboxylic acid (FowpEN™ 2; FowpDEN AND STEWARD!8), which 
BUTANOL - ACETIC ——p. 

St PHENOL 
eric ——P> 
BUTANOL - AO! 

ig 
Figs. 5 and 6. The ninhydrin-reactive, alcohol-soluble compounds of the seeds of Baikiaea plurijuga. 
Fig. 5: Prior to reduction. Fig. 6: After catalytic hydrogenation; note the conversion of baikiain 
(brown) to pipecolic acid (purple). “Unknown A” (purple) is now known to be 5-hydroxypipecolic 
acid (cf. Fig. 7). 
References p. 42 
