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

last step (Scheme 3.8). Pmtected vinylglycine was synthesizeâ in 18% overall yield from
methyl crot~nate.~~~
Scheme 3.8
A three step synthesis of vinylglycine via a Neber rearrangement of a N-
chloroirnidate 3.23 intermediate was reported in 50% overall yield.j6 The use of cheap
and convenient reagents makes this racemic synthesis of vinylglycine attractive,
particularly since an enzymatic resolution method is also described.
Scheme 3.9
3.1.3 Synthesis of Optically Active Vinylglycine
Optically active vinylglycine was first synthesized in 1980 in 54% yield3' via a
thennal degradation of L-methionine 3.24 and an improved methodology amenable for
large-scale synthesis has since been published (Scheme 3. IO)."
Na'04
O
Scheme 3.10
148Oc, -C02Me + ~ C 0 2 M e 6N HCI,
3 mm
NHCbz NH3 I
NHCbz NHCbz
-28'"
3.25 3.26 3.27
3.7