A new synthesis of djenkolic acid.

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. Van Veen and Hyman suggested that the natural synthesis of djenkolic acid in the plant might occur by a condensation of formaldehyde and cysteine. Such thioacetals were apparently not formed by condensation of these compounds under conditions studied at that time or later by various workers (3-G). Whenever aldehydes or ketones w&e caused to react with cysteine, the product was either an addition compound (I) or a thiazolidinecarboxylic acid (II).