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

(Cbz=@), 128.5, 128.2, 128.1 (a-=), 107.9 (OB0 ester GO), 72.7 (OB0 ester
-
CW), 67.0 (Cbzm20), 53.4 (am, 52.8 (CO&H3), 42.3 (y-I), 35.6 (OB0 ester
- CC&), 30.6 (B--2), 14.2 (OB0 ester Cm3); ESI-MS (M + H+) 457.89, 459.90. Anal.
calcd for Cl9H2&N@: C, 49-79; H, 5.28; N, 3.06. Found: C, 50.12; H, 5.48; N, 3.10.
4.4=42 D imethyl-2-[(~-2-[(be~Ioxy)cat.bonyl]~bi-
cycio[2.2.2 ]O&-1-yl)ethyi]mdonate, Cbz-L-GIu(y COOMe)(OMe)-OBO, 4.1 13.
Cbz-L-Glu(0Me)-OB0 ester 4.69 (0.140 g, 0.37 mmol) was dissolved in a flask in dry
THF (5 mL) and then transferred via cannula to a second flask containing LiHMDS (1.1 I
mL, 1.1 1 mmol) in THF (5 mL) at -78°C under Ar. Mer 1 hour, methyl cyanoformate
(35 pL, 0.44 mmol) was added by syringe. After 2 hours the reaction mixture was
poured into Et20 (80 rnL) and extracted with 3% N&CI (20 mL), saturated NaHC03 (20
mL), brine (20 mL) and dned over MgS04. The solvent was removed in vacuo to reveal
a light oil which was Mer purifed by flash chromatography (1:l EtOAc:Hex, 0.5%
Et3N) to give a clear oil in 68% yield (0.1 10 g).
[al2'~ = -24.4 (C = 1.2, CH2C12); TLC (l:l, EtOAcHex), Rr = 0.46; 'H NMR (Acetone-
dg, 300 MHz) 8 7.40-7.27 (m, 5H, Atm, 5.78 (d, lH, J = 10.2Hz, NH), 5.10 (d, 1H. J =
12.6Hz, CbzCHIfO), 5.00 (d, LH, J = 12.6Hz, CbzCHHO), 3.92-3.86 (s + m, 7H, OB0
ester CH20, a-CH), 3.65 (s, 3H, C&CH3), 3.63 (s, 3H, C02CH3), 3.50 (dd, 1 H, J = 5.6,