Reaktionsschritte
To a solution of 2-(dimethylamino)acetaldehyde (4.79 g, 38.8 mmol) in methanol (50 ml) and 1,2-dichloroethane (DCE) (25 ml) was added (3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-(2-(4-chlorobenzylamino)acetyl)-9-hydroxy-1-isopropyl-5a,5b,8,8,11a-pentamethyl-3a,4,5,5a,6,7,7a,8,9,10,11,11a,11b,12,13,13a-hexadecahydro-3H-cyclopenta[a]chrysen-2(5bH)-one (15) (5 g, 7.75 mmol) at 000° C. The pH was adjusted to 7 with Et3N. The reaction mixture was stirred at rt for 1 h. Sodium cyanoborohydride (0.487 g, 7.75 mmol) was added and the mixture was stirred overnight. The reaction was diluted with water (40 ml), and extracted with DCM (60 ml×3). The combined organic layer was washed with brine (20 ml), dried over sodium sulfate and filtered to afford crude product (3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-(2-((4-chlorobenzyl)(2-(dimethylamino)ethyl)amino)acetyl)-9-hydroxy-1-isopropyl-5a,5b,8,8,11a-pentamethyl-3a,4,5,5a,6,7,7a,8,9,10,11,11a,11b,12,13,13a-hexadecahydro-3H-cyclopenta[a]chrysen-2(5bH)-one (52) (5 g, 5.89 mmol, 76% yield) as a light yellow solid, which was used in the next step. LC/MS: m/z calculated 678.5. found 679.3 (M+1)+.
