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

Cbz-Asp(p-Me)(OMe)OBO ester 5.41 (0.200 g, 0.53 mmol) was dissolveci in THF (IO
mL) and cooled to -78°C while stimng under Ar. LDA (7.0 mL, 10.5 mmol) was added
and the mixture stirred for 1 h before being poured into Et20 (50 mL) and extracted with
3% NHKI (10 mL), 10% NaHC03 (10 mL), bine (10 mi,) and dried over MgS04. The
solvent was removed in vacuo and the resulting oil purified by flash chromatography to
give 0.052 g of 5.41 (26% yield) and 0.046 g of 5.42 (23% yield).
TU3 (1 : 1, EtOAc:Hex), Rf = O S 1 ; 'H NMR (Acetone-&, 300 MHz) 6 7.40-7.28 (m. SH,
Am, 5.88 (d, 1H. J = 10.4Hz, Nn), 5.1 1 (d, lH, J = 12.6Hz. CbzCHHO), 5.07 (d, 1H, J
= l2.6H.2, CbzCHHO), 3.94 (dd, lH, J = 3.8, 10.4Hz, a-CH), 3.86 (s, 6H, OB0 ester
CH20), 3.58 (S. 3H, C02CH3), 2.91 (ddd, lH, I r 3.6.6.9, 10.7&, p-CH), 1.12 (d, 3H, J
= 7.3Hz, f3-CH3), 0.80 (S. 3H. OB0 ester CC&); "C NMR (Acetone-&, 75 MHz) 6
174.6 (C=O), 156.4 (CONH), 136.6, (Cbz