Reaction Steps
After displacing the air with N2, palladium on charcoal (10%, 5.00 g, 47.00 mmol, 0.32 equiv) was added followed by the addition of a solution of [1-benzyl-3-(benzyloxy-carbonyl-isobutyl-amino)-2-hydroxy-propyl]-carbamic acid hexahydro-furo[2,3-b]furan-3-yl ester (78.36 g, 148.80 mmol, 1 equiv) in tetrahydrofurane. For a few minutes vacuum was applied and replaced by H2. After stirring for 24 h at room temperature. N2 was then introduced in the flask to displace the remaining H2. The palladium catalyst was removed by filtration over a bed of dicalite under N2 and the filter was washed with tetrahydrofurane. The filtrate was evaporated under reduced pressure. (58.40 g, 148.80 mmol, quantitative). LRMS (ES+): m/z 393 [M+H]+; 1H-NMR (CDCl3) δ0.91 (d, 3H, CH3), 0.93 (d, 3H, CH3), 1.45-1.57 (m, 2H, CH2, H4), 1.58-1.83 (m, 1H, CH (isobutyl)), 2.43 (dd, 2H, CH2—N (isobutyl)), 2.66-2.81 (m, 3H, CH2—N and CH of CH2C6H5), 2.87-2.96 (m, 1H, CH, H3a), 3.06 (dd, 1H, CH of CH2C6H5), 3.51-3.57 (m, 1H, CH2, H5), 3.67-3.75 (m, 2H, CH and CH2, H2), 3.81-3.93 (m, 2H, CH—OH and CH2, H5), 3.94-4.00 (m, 1H, CH2, H2), 5.01-5.08 (m, 1H, CH, H3), 5.10 (d, 1H, NH), 5.64 (d, 1H, CH, H6a), 7.16-7.31 (m, 5H, C6H5).
