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

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

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

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TU3 ( 1 : 1, EtOAc:Hex), Rr = 0.40; 'H NMR (Acetone-&, 300 MHz) 6 7.37-7.22 (m, SH,<br />

ArH), 5.44 (d, lH, J = 10.2H2, NH), 5.07 (m, 2H, CbzCH20), 4.19 (dd, lH, J = 3.7,<br />

10.2Hz, $-CH), 3.95-3.79 (s + m, 7H, OB0 ester CHD, &CH), 3.67 (S. 3H, C02CH3),<br />

0.80 (s, 3H, OB0 ester CC&); 13c NMR (Acetone-d6, 75 MHz) 6 172.3 Ca), 156.6<br />

(CONH), 136.4, (Cbz=C=), 128.2, 127.9, 127.6 (Ch-=), 108.1 (OB0 ester C-O),<br />

72.3 (OB0 ester _&O), 66.8 (CbzCHzO), 59.9 @-CH), 52.1 (CO&H3), 52.2 (a-CH),<br />

30.4 (OB0 ester CCH3), 14- 1 (OB0 ester Ca& FMR (cast fiom CH2C12) 3432, 2962,<br />

2884,2122, 1729, 1515, 1048; ESI-MS (M + 406.91; Anal. caicd for C18H22N4@: C,<br />

53.20; H, 5.46; N, 13.79. Found: C, 53.54; H, 5.85; N, 13.85.<br />

5.4.22 Methyl-(~)-3-aminol21[(bellzyloxy)carbonyl]amin012-(4-methyl-2,6,7-<br />

trioxabicyclo[2.2.2]0~t-1-yl)pmpanoate, Cbz-L-Asp(B-NH2)(OMe)OB0 ester, 5.54.<br />

Cbz-L-Asp(P-N3)(OMe)OB0 ester 5.53 (0.1 14 g, 0.28 mrnol) was combined with PhsP<br />

(0.088 g, 0.33 mrnol) <strong>and</strong> dissolved in dry THF (5 rnL) then stirred at room temperature<br />

for 24 hours. Distilled water (20 pL) was then added <strong>and</strong> the mixture refluxed for 3<br />

hours. The solvent was removed under reduced pressure to give a white solid that was<br />

purified by flash chromatography (9: 1, EtOAcMeOH 0.5% WOH) to give 5.54 in 67%<br />

yield (0.07 1 g).

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