N-tert-butoxycarbonyl O-allyl L-seryl L-valyl L-valine methyl ester → O-allyl L-seryl L-valyl L-valine methyl ester

Participants

Reaction Steps

N-tert-butoxycarbonyl O-allyl L-seryl L-valyl L-valine methyl ester (8) (6.80 g, 14.9 mmol) was stirred in formic acid (70 mL) at room temperature for 9 hours and the formic acid evaporated. The residue was diluted with 110 mL water and the aqueous solution washed with Et2O (3×30 mL). The pH was adjusted to pH 9 by addition of solid K2CO3 and the resulting solution extracted with EtOAc (3×55 mL). The combined organic extracts were washed with saturated brine (30 mL) and dried with anhydrous MgSO4. The solvent was evaporated affording a white solid (4.35 g, 82%); δH (200 MHz; do-DMSO) 8.26 (1H, d, J 8, NH(Valx)), 8.03 (1H, d, J 9, NH(Valy)), 5.85 (1H, ddt, J 5, 10 and 17, CH═CH2)), 5.24 (1H, ddt, J 1, 3 and 17, CH═CHH), 5.12 (1H, ddt, J 1, 3 and 10, CH═CHH), 4.36 (1H, dd, J 6 and 9, CαH(Valy)), 4.12 (1H, dd, J 6 and 8, CαH(Valx)), 3.93 (2H, dt, J 1 and 5, CH2CH═CH2), 3.61 (3H, s, OCH3), 3.49 (2H, d, J 5, CH2,), 3.43-3.39 (1H, m, CαH(Ser(All))), 2.38 (2H, br s, NH2), 2.12-1.86 (2H, m, CH(CH3)2), 0.91-0.78 (12H, m, CH3)

Provenance & Evidence