Reaction Steps
To a solution of (3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-1-isopropyl-5a,5b,8,8,11a-pentamethyl-3a-(2-nitroethyl)-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-9-yl acetate (27) (10 g, 18.46 mmol) and nickel(II) chloride (7.18 g, 55.4 mmol) in methanol (100 ml) was added sodium borohydride (6.98 g, 185 mmol) portionwise during 1 hour. The reaction mixture was stirred at 0° C. for 1 h. The mixture was diluted with EtOAc (250 mL). The organic phase was washed with sat. NH4Cl (50 mL) until the organic layer change to colorless. The combined organic layers were dried over anhydrous Na2SO4, and concentrated in vacuo to get the crude product (3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-(2-aminoethyl)-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-9-yl acetate (34) (7 g, 12.63 mmol, 68.4% yield), which was used without further purification. 1H NMR (400 MHz, CHLOROFORM-d) δ=9.15 (dd, J=4.9, 11.4 Hz, 1H), 8.12 (br. s., 2H), 7.97-7.81 (m, 1H), 7.63-7.49 (m, 1H), 7.26-7.15 (m, 1H), 7.15-7.04 (m, 1H), 6.98 (d, J=18.6 Hz, 1H), 6.81-5.38 (m, 47H); LC/MS: m/z calculated 511.4. found 512.3 (M+1)+.
