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

(CbzQI20), 57.4 (am, 39.8 (yCJS2), 30.4 (OB0 ester CCH3), 28.5 (a3)C) 13.7
(OB0 ester Cm3); IR (cast h m C&C12) 35 15, 3452, 2973, 2934, 288 1, 1726, 15 13,
1366, 1279, 1225, 1 153, 1047; ESI-MS (M + H+) 438.21; Anal. calcd for C22H3iN08: C,
60.40; H, 7.14; N, 3.20. Found: C, 60.63; H, 7.34; N, 3.26.
4.4.35 1-[(2,4,6-TriiSopropyIphenyI)SUEfonyl]~ Trisy1 azide,
4.105.
2,4,6-Tnisopropylbenzenesulfonyl chloride (3.94 g, 13.0 mol) was added to a stimng
mixture of NaN3 (2.53 g, 39.0 mrnol) in Hz0 (20 mL). Acetone (40 rnL) was
immediately added and the solution stirred for 5 hours. The mixture was then extracted
with Et20 (3 x 50 mL), the organic layers pooled and then extracted with H20 (30 mL),
brine (30 mL) and then dried over Na2S04. The solvent was removed in vacuo to reveal
a crearn coloured oïl which crystallized on standing to give 3.40 g (85% yield) of 4.105
which was used without further purification.
'H NMR (Acetone-&, 300 MHz) 7.43 (S. 2H, Adf), 4.06 (septet, 2H. J = 6.8Hz,
(CH3)2CH), 3.03 (septet, 1 H, J = 7.1 Hz, (CH3)2CH), 1-29 (d, 1 2H, J = 6.8Hz. (Ca)2CH),
1.26 (d, 6H, J = 7.1Hz, (cH3)2CH); 13c NMR (Acetoned, 75 MHz) 6 155.7 (A-=)
15 1.2 (Ar--C-=), 132.3 (Ar-iJ=), 124.8 (Ar=C-Hz), 34.5 ((CH3),CH), 30.2 ((CH3)sH),
24.4 ((CH3)2CH), 23.2 ((CH3)2CH).