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

7.3&, CHZCH~), 0.78 (s, 3H, OB0 ester CCH3); I3c NMR (Acetone-a, 75 MHz) 6
175.9 E=O), 156.3 GONH). 137.6 (Cbz===), 128.3, 127.7, 127.7 (Cbz==H=), 108.3
(OB0 ester C-O), 72.4 (OB0 ester w20), 65.7 (Cb2m20), 53.3 (a-CH), 50.7
(COa3). 43.2 (y-), 3 1.6 @-CH*), 30.3 (CCH3). 24.3 a2a3), 13.4 (OB0 ester
Cm), 10.8 (CHCH3); IR (cast fiom CHC13) 3359, 2962, 2879, 1730, 1517, 1457,
1230, 1047, 1009; HRMS (FAB) calcd for (M + H+) C2iH3flQ 408.20224, found
408.20133. Anal. calcd for C21bN07: C, 61.90; H, 7.17; N, 3.44. Found: C, 61.70; H,
7.16; N, 3.45.
4A. l'l 5-Metbyl-(~,4S)-2-[~tl~y10xy)carbonyl]P-
2,6,7-trioxa-bieyei0[2~2~2 Joct-1-yI)ethyI]-pentanmte, Cbz-L-GIu(~AUyl)(OMe)-OB0
ester, 4.79.
Cbz-L-Glu(0Me)-OB0 ester A69 (0.232 g, 0.61 mmol) was dissolved in dry THF (30
mL) then cooled to -78°C whilst stimng under Ar. In a second flask, LiHMDS (1.83
mL, 1.83 mmol, 1.OM in THF) was added to dry THF (5 mL) then cooled to -78°C
w hilst s timng under Ar. The Cbz-L-Glu(0Me)-OB0 ester 4.69 was then transferred
dropwise to the second flask via cannula The mixture was allowed to stir at -78°C for 1
hour before allyl brornide (0.25 mL, 3.05 mmol) was added by syringe. The mixture was
allowed to stir for 6 hours at -78°C before king poured into 3% m l
(20 mL) and
extracted with EtzO (100 mL). The organic layer was then extracted with 3% Nwl (20
mL), saturated NaHC03 (20 mL), bnne (20 mL) and dried over MgS04. The solvent was
removed in vacuo to reveal a yellow oil which was further purified by flash
chromatography (1 : 1 EtOAc:Hex, 0.5% Et3N) to give a clear oil in 78% yield (0.199 g).