Several years ago considerable interest was aroused by the discovery
by van Veen and Hyman (1) of a new naturally occurring sulfur-containing
amino acid which they had isolated from the djenkol bean (Pithecolobium
lobatum) and named djenkolic acid.
They showed that it was probably
the cysteine thioacetal of formaldehyde. This structure was confirmed
by du Vigneaud and Patterson (2) who synthesized the I-cysteine thioacetal
of formaldehyde by the condensation of methylene chloride with 2 moles
of I-cysteine in liquid ammonia and showed their synthetic compound to
be identical with the naturally occurring djenkolic acid.