Synthesis of Valine and Isoleucine in Primitive Earth Conditions

SYNTHESIS of small amounts of valine, isoleucine and leucine from the polymerization of ammonium cyanide solutions has been reported1,2 in addition to the substantial yields of glycine, alanine, aspartic acid and serine3. We have been unable to find any valine, isoleucine or leucine synthesized by the polymerization reaction of NH4CN alone. On adding acetone or methyl ethyl ketone to the NH4CN solutions, significant yields of valine, alloisoleucine and isoleucine are, however, obtained. The previous identifications were based on the elution pattern from a Beckman1 automatic amino-acid column4. Because several non-protein amino-acids appear at the same elution positions as valine, isoleucine and leucine5,6 (for example, isoasparagine elutes with isoleucine), an error of identification is possible, although the specific amino-acids in this case are not known. We have used a more elaborate separation scheme to avoid the problem of overlapping peaks.