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

addition of the enolate of Cbz-Gly ethyl ester 2-15 to various carbonyl denvatives and
subsequent cyclization to the 2-oxazolidone 2.16 intemediate followed by acid
hydrolysis gave the p-alkyl and B-diaikyl-p-hydroxy-rhreo-a-amino acids in excellent
yield.
R +
O
RCHO + cUNH2 W, '2~'~
( ~ e & i ) CO~S~M~,
~ P
Scheme 2-1
Si "Cl
O,# H2
Scheme 2.2
~'4, Me
2) HCVEtOH R2=Me, Pr, Ph
C ~ Z H ~ C O ~ E ~
3) dil. HC1
2.1 5
O NH
K O - R2:2H
HCI
H2
2.16
RI*, Me
Fl24e, Pr, Ph
2. 1.3 Synthesis of Optically Active PHydroxy- a-Amino Acidr
2.1.3.1 Enzylll~ltic Synthesis of /%Hydrom-a-Amino Acids
Various groups have tried to use the intrinsic chirospecificity of enzymes to
synthesize fi-hydroxy-a-arnino acids with varying degrees of success. Saeed and Young
first repocted the use of serine hydroxymethyltransferase (EC 2.1.2.1) in 1992 using the
enzyme to couple glycine with various aldehyde~.~ However, the products were
46