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

The crude product was fiitered through Celite to remove some of the by-product Ph90.
The filtrate was then concentrated to a viscous liquid and hexane (500 mL) was added.
The mixture was filtered once more through Celite to remove most of the by-product
Ph3P0. The filtrate was concentrated to obtain a viscous yellow oil. The crude product
was distilled under vacuum with a fractionation column. Oxetane bromide 2.39 was
collected as a viscous liquid in 95-99% (8 1 .O g) yield.
bp 62-64"C/lO mm Hg; 'H NMR (CDC13, 250 MHz) 6 4.464.38 (d+d, 4H, J = 6.3Hz,
CHzO), 3.65 (s, 2H, C&Br), 1.44 (s, 3H CCH3); 13c NMR (CDC13, 63 MHz) 6 80.5
CH20), 41.3 cH2Br), 40.5 (CCH3), 22.3 (Cm3). IR (neat) 2960, 1453, 1233; ESI-MS
(M + H+) 157.21, 159.22; Anal. Calcd for C5H9Br0 : C, 36.39; H, 5.50. Found : C,
36.50; H, 5.70.
Procedure B: To a stirred solution of oxetane alcohol (20.4 g, 0.20 mole),
triphenylphosphine (63.0 g, 0.24 mole), and pyridine (39 ml, 0.48 mole) in 200 ml
CH2Q was slowly added a solution of bromine (10.2 mL, 0.2 mol) in 50 mL of CHzClz
at 0°C. The mixture was stirred at room temperature for one hour. The solvent was
rernoved under reduced pressure. To the residue was added Et20 (400 mL) and the
mixture then filtered through Celite and the filtrate evaporated in vacuo. Hexanes (200
mL) was then used to rinse the remaining solids. The final filtrate was concentrated and
distilled to give the product 2.39 (22.7 g, 69%).