Sodium borohydride → 1-[2-(3,4-Methylenedioxyphenyl)-2-hydroxyethyl]-4-[3,4-dihydro-2(1H)-quinazolinon-1-yl]-piperidine

In this example, 2.70 g of 1-(3,4-methylenedioxybenzoylmethyl)-4-[3,4-dihydro-2(1H)-quinazolinon-1-yl]-piperidine and 150 ml of methanol are mixed and stirred under ice-cooling. Then, 2.0 g of sodium borohydride is added to the stirred mixture over a period of one hour. Subsequently, the mixture is brought back to room temperature and stirred for 3 hours at room temperature and the reaction solution is concentrated. The resultant residue is mixed with 50 ml of water and the mixture is extracted with ethyl acetate (100 ml×2 and 50 ml×1). The extract is washed with water, dried and concentrated. The resultant viscous residue is mixed with 5 ml of methanol. The crystals deposited are separated by filtration, washed with methanol and dried to obtain 2.05 g of a crude product. The crude product is recrystallized from hot ethanol to obtain 1.74 g of the desired product.