Solution and Solid Phase Synthesis of Unusual a-Amino Acids From

generally proposed to proceed as outiiwd in scheme 3.111G"f although a more recent
article suggests a süghtiy different version as shown in scheme 3.2."
Scheme 3.1
bbt%~3
3.9
Nu-Enz
Enz
I O
NU- CO2
The aldimine 3.9 initially generated is the amino acid-PLP intemediate that the
enzyme normaily foms with amino acid substrates. However, with suicide substrates,
once the reactive 1.4-addition site is unmasked by decarboxylation or proton abstraction,
an irreversible addition by an active site nucleophile to give 3.11, 3.13 or 3.15 occurs.
Some of the more recent vinylglycine related inhibitors include a-allenic-a-amino acids
(suicide substrates of Vitamin Bs linked decarboxylase)'* and a D-vinylglycine containing
peptide (a mechanism based inactivator of peptidylglycan a-hydroxylating
In some pyridoxal phosphate dependent enzymes, vinylglycine anaiogs are
important intermediates in the enzyme mechanism and lead to products instead of
inhibition.' lb-1 lf.12.16 Vinylglycine has been used as a probe of 1 -arninocyclopropane- 1 -
carboxylate synthase (ACC)17 and to determine the mechanism of desulfurization of L-
cysteine by the nifS gene product in Azobacter vinlandii."
106