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

4.1.1 Isolation
Chapter Four
y-Substituted glutamic acids have receiveci significant attention recently due to
both their diverse biological activity and synthetic significance. Various glutamic acid
denvatives have been isolated from natural sources, beginning with the isolation of y-
methylglutamic acid 4.1 (Scheme 4.1) from the fem Phyllitis scolopendrium in 1955 and
subsequenily from numerous other plants including the mushmom Mycena pura.' y-
Ethylglutamic acid 43 has been found in varying concentrations in Wagatea spicuta and
the seeds of the Caesulpinia species.'
y-Hydroxyglutamic acid 4.4 was fmt isolated from the plant Phlox decussatd and
later as a metabolite in the Hemerocallis species.lb Both (2S.4R) and (2S,4S)-y-
hydroxygiutamic acid have been found to be constituenu of natural product skeletons,
including the potent epileptogenic dysiherbaine 4.5 isolated from the marine sponge
Dysidea herbacea4 and the sweetener, monatin 4.6 isolated from Schlerochiton
ilicifoliud The Lthreo diastereomer of B-hydroxyglutarnic acid 4.7 was first iden ti fied
in the natural product, antibiotic S-520, obtained from Streptomyces diustaticos in 197OO6
This a-amino acid has been used in the synthesis of other naturai products, most
noticeably trïcolomeric acid 4.8 and its analogs, which have insecticidal activity.' &y-
dihydroxyglutamic acid 4.9 was isolated from the seeds of Lepidiwn sativium and leaves
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