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

product,13 as in the case of L-a-methyldopa" The Bücherer-Bergs synthesis is a
modification of the Strecker synthesis proceeding through a hydantoin intermediate?
In the Gabriel synthesis, ammonia is replaced with potassium phthalidde 1.1 as
the aminating reagent, generally resulting in fewer side reactions (Scheme 1 .2).12
R + G N
O
K -
Scheme 1.2
@( acid/alkali acid or or R
XAC02Et
O O
cogt
hydrazine/acid5 CO,Et
Hz
Racemic syntheses are still cornmonly used even though the literature on
stereospecific syntheses over the past decade has grown immensely. A recent procedure
describes the amination of 2-bromocarboxylic esters 13 with trichloroacetamide 1.2
(Scheme 1.3) giving the free amino acid in 40-908 yield.I6
1.2.2 Alwtion of Glycine Derivatives.
Scheme 1.3
K CO u
phase
transfer
catalyst
KOH ,
MeOH
The strategy of adding the side chain of an amino acid to a glycine equivalent was
first reported by Sorensen in 1903" and since then a number of varied templates have
been used. N-Acylaminornalonates 1.4 provide a versatile route (Scheme 1 -4) where