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

'H-NMR @20, 300 MHz) 6 7.26-7.03 (m. 5H, ArH), 4.194.07 (m, lH, a-CH), 3.1 1-
2.99 (m. lH, P-CH), 2.78-2.56 (m, 2H. PhcH2); 13c NMR @20, 75 MHz) G 176.3
54.17 Methyl-(2S~S)-3-metbyl~(4-wthyl-2,6,7-tno~bi~yc10[2~2~2]~t-l-y1)-2-
(trityiamino)propan08te, Tr-L-Asp@-Me)(OMe)OBO ester, 5.50.
Cbz-Asp(f3-Me)(OMe)OBO ester 5-41 (0.360 g, 0.95 mmol) was dissolved in
Et0Ac:EtOH (1 : 1, 40 mL) to which Pd/C (0.5 g, Depssa type E 1 O1 NUW) was added.
The mixture was then evacuated and purged with H2 which was repeated twice. The
mixture was stirred for 12 h before king filtered through celite and the filtrate reduced in
vacuo to reveal a yellow oil. Dry CH2CI2 (10 mL) and DlPEA (0.26 rnL, 1.88 rnmol)
was added followed by trityl chloride (0.262 g, 0.95 mmol). The mixture was dlowed to
stir for 6 h before king poured into Et20 (100 mL) and extracted with 3% -1 (3 x 20
mL), 10 % N e03 (20 mL). brine (20 mL) then dried over MgS04. The solvent was
removed under reduced pressure to reveal a white foam which was recrystallized from
Et20:Hex to give 0.332 g (73%) of small cube shaped crystais.