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

concentrateci reaction mixhue of 4.114 (1 .O M) reporteci by Lubell and Lombart was not
necessary for the formation of 4.117.
Table 4.3: Claisen condensation of 4.69
Scheme 4.32
Enîry Base Temp.(OC)
Time
(h) [4.69](M) 4.69
Yield
4.117 4.72
1 NaHMDs
(1.5 eq)
-78°C 2 0.5 95 - -
18
3 -30°C+ rt 1 .O 48 - 32
(3 eq)
4
LiHMDS -780~ 18 0.5 18 33 -
6 L~HMDs ooc 2 O. 1 25 3 1 -
(1.5 eq)
4.2.9 Deprotection of pSubstituted Gluturnic Acids
Acid hydrolysis has been used extensively to deprotect y-substituted glutamic acid
de ri vat ive^.^^'^ In our case refluxing 6N HCl gave ysubstituted glutamates in good
yield. Reflux periods of beh~een 2-4 hours were required to fully hydrolyze the
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