Notes

Abstract

IN addition to the forty ketones which are capable of degrading a-amino-acids to the corresponding aldehydes or ketones with one carbon atom less (Schonberg, et al., J., 1948, 176), the nitrogen analogues of o-and fi-quinones (e.g. , phenanthraquinone-imine, indophenol, and 2 : 6-dichlorophenol-indophenol) effect this change in boiling water. It is uncertain whether they act directly or after hydrolysis ; e.g., phenanthraquinone-imine is very easily hydrolysed to the quinone and it is possible that the observed reaction is due to this compound. However, even if they themselves react, they probably do so in a similar manner to the quinones (cf. Schonberg et al., loc. cit.).Recently, Moubasher (J., 1951,231) found that piperonaldehyde very slowly effected the same change in boiling water, and Baddar (J., 1949, S 163) described a number of such degradations with nitrobenzaldehydes in 75% aqueous pyridine. It has now been found that fluorenone, which is inactive in neutral solution, degrades alanine, a-aminoisobutyric acid, leucine, and valine in the same mixed solvent in good yield.Experimental.-Action of phenanthraquinone-imine, indophenol, and 2 : 6-dichloro~henol-indophenol on leucine. The quinone-imine (0.5 g.), leucine (0.6 g.), and indophenol (0.5 g.) or 2 : 6-dichlorophenolindophenol (0.6 g.) were mixed with water (50 c.c.) in a Claisen flask fitted with a n upright condenser, to which were attached a Liebig condenser and a receiver. With a continuous current of carbon dioxide passing through it, the mixture was distilled until its volume was reduced to about 20 C.C. (1 hour). The distillate was collected in a receiver containing a solution of 2 : 4-dinitrophenylhydrazine (0.3 g. in 25 C.C. of alcohol). The contents of the receiver were treated with concentrated hydrochloric acid (5 c.c.) and cooled in ice ; isovaleraldehyde 2 : 4-dinitrophenylhydrazone was obtained and identified by its m. p. and mixed m. p. With phenanthraquinone-imine the yield was about loyo, but with the other two compounds it was smaller.The experiment was carried out as above but with fluorenone (1 g.) and alanine (0.5 g.), a-aminoisobutyric acid (0.5 g.), leucine (0.6 g.), or valine (0.7 g.), and aqueous pyridine (50 c.c., 75% by-vol.) for 3 hours; acetaldehyde, acetone, isovaleraldehyde, and isobutaldehyde, respectively, were obtained as their 2 : 4-dinitrophenylhydrazones, identified by m. p. and mixed m. p. Action of fluorenone on a-amino-acids in aqueous pyridine.The yield in each case was more than 30%.