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

minutes. The akohol solution was transferred slowly by cannula to flask 2 over a period
of 15 minutes and then rinsed with CH2C12 (5 mL). The resulting cloudy, white mixture
was stimd for 1.5 hours at -78OC. DIPEA (3.35 m . 19.4 rnrnol, 5.0 equiv) was added
and the solution stirred for 30 minutes at -7g°C and 10 minutes at O°C. Ice-cold CHzClz
(100 mL) was added and the solution was washed with ice-cold 3% NWl(2 x 80 mL),
saturated NaCl (1 x 80 mL), dried (MgSOd), and evaporated to dryness to yield a light
coloured foam ( 1. log) in 99% yield.
[~]~Os78= -44.8 (c = 1.02, CHXl2); TU3 (1 : 1, Et0Ac:Hex) Rf = 0.58; 'H NMR (mli,
250 MHz) 6 9.64 (s, 1H, CHO), 5.07 (br d, lH, J = 7.8H.2, NH), 4.48 (d, lH, J = 7.8Hz,
a-CH), 3.91 (s, 6H, OB0 ester CH20), 1.41 (s, 9H, (CH3)3C), 0.79 (s, 3H, OB0 ester
CCH3); 13c NMR (Cml3, 63 MHz) 6 195.7 (CHO), 155.6 EONI-I), 107.3 (OB0 ester
C-O), 80.1 ((CH3)3C), 72.8 (OB0 ester CHzO), 63.3 (a---, 30.9 (OB0 ester CCH3),
28.2 ((CH3)3C), 14.3 (OB0 ester CcH3); IR (cast from CH2C12) 3374, 2973, 1716, 1506,
1166, 1046; HRMS (FAB) calculated for (M + HC) c13HUN06 288.1447, found
288.1425. Anal. calcd for C13H21N06: C, 53.78; H, 8.33; N, 4.83. Found: C, 53.98; H,
8.56; N, 4.89.
2.4.9 1-[NJerf-Butoxyarbonyl-(lS)-l-amino-2~xopropyl]4-methy1-2,6,7-
trioxabicyclo [2*2.2J0~tPw, Bor-L-Thr(ket)OBO ester, 2.47.