1.3 g (3.3 mmol) of (±)-trans-2-diethylaminocarbonyl-8a-(3-methoxyphenyl)-3-methyl-4,4a,5,6,7,8,8a,9-octahydro-1H-pyrrolo[2,3-g]isoquinoline, 0.28 ml (4.95 mmol) of acetic acid, 0.33 ml (3.96 mmol) of 2-furaldehyde were dissolved in 50 ml of MeOH under nitrogen atmosphere. 0.415 g (6.6 mmol) of sodium cyanoborohydride were added and the solution stirred for 15 h. Additional acetic acid (0.1 ml), 2-furaldehyde (0.3 ml) and sodium cyanoborohydride (0.2 g) were added. After two hours of stirring the reaction mixture was cooled to 0° C. and 50 ml of 5N hydrochloric acid were added. The solvent was removed in vacuo, the aqueous solution was extracted with Et2O, the pH was adjusted to 8 with 20% NaOH and then extracted with AcOEt. The organic layer was dried over Na2SO4 and the solvent was removed in vacuo. The crude product was dissolved in acetone/MeOH and the solution brought to acidic pH with HCl/Et2O . The precipitate was filtered, yielding 1.7 g of the title compound. M.p.=105° C. dec.
