Reaction Steps
A mixture of protected tripeptide 5 (0.50 g, 0.79 mmol) and 10% palladium on activated carbon (0.08 g, 0.08 mmol) in 20% water/methanol (100 cm3) was stirred under an atmosphere of hydrogen at room temperature for 20 h. The solution was filtered through a Celite™ pad, washed with methanol (60 cm3) and the filtrate evaporated to dryness to form a clear gum. This gum was dissolved in methanol (30 cm3) and refiltered through a Celite™ pad. The solution was evaporated to dryness to form a clear gum. The gum was placed on a vacuum line for 15 min and then triturated with anhydrous diethyl ether to form GHypE (0.20 g, 80%) as a white solid. GHypE was shown to be an 80:20 trans:cis mixture of conformers by 13C NMR analysis (the ratio was estimated from the integration of the signals at 6 70.2 and 68.5, assigned to the Proγ-C of the major and minor conformers respectively): mp 158-160° C.; [α]D −58.1 (c 0.1 in MeOH); δH (300 MHz; D2O) 1.96-2.23 (4H, m, Gluβ-H2, and Proβ-H2), 2.48-2.56 (2H, m, Gluγ-H2), 3.62 (2H, d, J 10.0, Glyα-H2), 3.80 (1H, dd, J 8.8 and 4.9, Gluα-H), 4.08 (1H, dd, J 10.4 and 2.6, Proα-H), 4.30-4.35 (2H, m, Proδ-H2) and 4.63-4.69 (1H, m, Proγ-H); δC (75 MHz, D2O) 29.2 (CH2, Gluβ-C), 31.7 (CH2, Proβ-C), 32.3* (CH2, Proβ-C), 37.6 (CH2, Gluγ-C), 40.0* (CH2, Glyα-C), 41.0 (CH2, Glyα-C), 54.8 (CH2, Proδ-C), 55.3 (CH, Gluα-C), 59.1* (CH, Proα-C), 59.7 (CH, Proα-C), 68.5* (CH, Proγ-C), 70.2 (CH, Proγ-C), 166.4 (quat., Gly-CO), 167.1* (quat., Gly-CO), 173.0* (quat., Pro-CON), 173.4 (quat., Pro-CON), 177.9 (quat., Gluα-CO) and 179.2 (quat., Gluγ-CO); m/z (FAB+) 318.1329 (MH+.C17H20NO5 requires 318.1342).
