99300-78-4

Synthesis

Venlafaxine (92.4 g) was dissolved in ethyl acetate (450 ml) at 50-55 oC, filtered hot then cooled to 10-15 oC and pH was adjusted to <2 with addition of isopropyl alcohol saturated with HCl gas and allowed to stand for 15 minutes. The white solid was filtered off, washed with EtOAc (75 ml), and then with petroleum ether (150 ml). The crystalline salt was dissolved in MeOH (160 ml) at 50-55 oC and filtered when hot. The hydrochloride salt 35 was precipitated by adding ethyl acetate drop-wise, at room temperature. After 4 hours the solid was filtered and washed with ethyl acetate (100 ml). The solid (98.3 g) was allowed to dry in air (6-8 hours).

Manufacturing Process

1-[Cyano(-methoxyphenyl)methyl]cyclohexanolp-Methoxyphenylacetonitrile (50 gm, 0.3 mole) was added to dry tetrahydrofuran (250 ml) and the solution cooled to -70°C under nitrogen. n- Butyl lithium in hexane (210 ml, 0.3 mole) was added dropwise, with stirring. The temperature was maintained below -50°C and a yellow precipitate appeared. After the addition was complete, the reaction mixture was maintained below -50°C for 30 minutes and cyclohexanone (35 ml, 0.3 mole)was added. After a further 45 minutes below -50°C the temperature was allowed to rise to 0°C and a saturated ammonium chloride solution was added. The layers were separated and the aqueous layer extracted with diethyl ether. The combined organic solution was washed with brine, dried over magnesium sulfate and evaporated. The product crystallized (25.2 gm, melting point 125°-127°C). The structure was confirmed by N.M.R. and mass spectral analysis.1-[2-Amino-1-(p-methoxyphenyl)ethyl]cyclohexanol1-[Cyano(p-methoxyphenyl)methyl]cyclohexanol (12 g, 0.05 mole) was dissolved on warming in a mixture of ammonia-ethanol (20% v/v, 250 ml) and hydrogenated in a Parr apparatus over 5% rhodium an alumina (2.8 gm). The catalyst was filtered, washed well with ethanol and the combined filtrate evaporated and dried under vacuum yielding an oil (12 gm). Thin layer chromatography: single spot, ninhydrin positive [chloroform-methanol-acetic acid (80:10:10 v/v)].1-[-2-Dimethyl-amino)-1-(4-methoxyphenyl)-ethyl]cyclohexanol1-[2-Amino-1-(p-methoxyphenyl)ethyl]cyclohexanol (12 gm; 0.048 mole) was treated with a mixture of formaldehyde (11 ml), formic acid (14.5 ml, 88%) and water (125 ml) and heated at 100°C for five hours. The reaction mixture was cooled and extracted with ethyl acetate. This extract was discarded. The aqueous residue was cooled in ice, rendered basic by the addition of solid potassium hydroxide, saturated with sodium chloride and extracted 3 times with ethyl acetate. The extract was washed with brine, dried over anhydrous potassium carbonate and evaporated to an oily residue (8 gm). This mixture of products was chromatographed on 1 kg of Mallinckrodt Silicar CC7 silica gel and the progress of the chromatography was monitored by thin layer chromatrography using a system comprising ethanol:2 N ammonia:ethyl acetate:cyclohexane 45:8:100:100 (v/v). Fractions containing the desired product were combined and the hydrochloride salt prepared using 4 N HCl in isopropanol. The yield of the free base was 4.6 gm of 1-[(2-dimethylamino)- 1-(4-methoxyphenyl)ethyl]-cyclohexanol. The hydrochloride (venlafaxine): melting point 215°-217°C. The structure was confirmed by mass spectral analysis and N.M.R. analysis.

Biological Activity

Dual serotonin/noradrenalin re-uptake inhibitor that displays ~ 30-fold higher affinity for SERT than NET (K i values are 82 and 2480 nM respectively). Antidepressant; increases swimming and climbing behavior in the forced-swim test in rats.

Biochem/physiol Actions

Venlafaxine is an antidepressant. The mechanism of the antidepresant action of venlafaxine in humans is associated with its potentiation of neurotransmitter activity in the CNS. Venlafaxine is a potent inhibitor of neuronal serotonin and norepinephrine reuptake and weak inhibitor of dopamine reuptake. Venlafaxine has no significant activity for muscarinic, histaminergic, or α-1 adrenergic receptors in vitro. Venlafaxine does not possess MAO inhibitor activity.

General Description

A Certified Snap-N-Spike? Solution suitable for many LC/MS and GC/MS applications from forensic or clinical toxicology analysis to urine drug testing. Also known by the brand name Effexor?, venlafaxine is an SNRI antidepressant approved for the treatment of major depressive and general anxiety disorders.