Synthesis of Each Stereoisomer of Phenylalanine and Evaluation of the Stereochemical Course of the Reaction of (R)-Phenylalanine with (S)-Phenylalanine Ammonia-lyase

Article abstract of DOI:10.1039/P19940003545

The four stereoisomers of <3-2H1>phenylalanine have been prepared, each as a single enantiomer in ca. 98percent diastereoisomeric excess and with ca. 99percent deuterium incorporation, by side-chain bromination of phenylalanine derivatives, followed by deuteriolysis of each of the diastereoisomeric product bromides with deuterium over 5percent palladium-on-carbon.The latter reactions proceeded with retention of configuration. (2R,3S)-<3-2H1>Phenylalanine reacted with (S)-phenylalanine ammonia-lyase to give <3-2H1>-trans-cinnamic acid, with 92percent deuterium incorporation, while the (2R,3R)-stereoisomer of the deuterated phenylalanine gave <3-2H1>-trans-cinnamic acid with 27percent deuterium incorporation.These results indicate that reaction of (R)-phenylalanine with the enzyme involves mainly loss of the 3-pro-R hydrogen and ammonia, in an antiperiplanar elimination process analogous to that previously reported for (S)-phenylalanine, while a minor pathway for reaction of (R)-phenylalanine is either isomerization to (S)-phenylalanine, before elimination, or synperiplanar elimination.

Full text of DOI:10.1039/P19940003545

View Article Online / Journal Homepage / Table of Contents for this issue

View Article Online

View Article Online

View Article Online