1,4-Dihydropyridine Compounds in Treating Hypertension

i. A mixture of acetoacetic ester (13.0 g) and 2-benzyloxyethanol (22.0 g) was stirred under reflux for 30 minutes. Distillation under vacuum yielded the crude product (21.5 g) which on re-distillation gave, as a colourless oil, acetoacetic acid 2-benzyloxyethyl ester (17.2 g), b.p. 124.degree.C/0.1 mm.

ii. A mixture of acetoacetic acid 2-benzyloxyethyl ester (30 g), o-trifluoromethyl benzaldehyde (11.2 g) and concentrated ammonia (8.0 ml of density 0.88) in ethanol (100 ml) was stirred under reflux for 24 hours and then poured into ice and water. The yellow oil which precipitated was separated, and solidified on addition of ethanol. Recrystallisation from ethanol gave 1,4-dihydro-2,6-dimethyl-4-(2-trifluoromethylphenyl)pyridine 3,5-dicarboxylic acid bis-(2-benzyloxyethyl)ester (10.4 g), as white crystals m.p. 141.degree.-142.degree.C.

iii. The bis-benzyl ether, produced in (ii) above, (8 g) was dissolved in ethanol and hydrogenated over palladium charcoal, Evaporation to dryness of the filtrate, produced on the removal of the catalyst, and recrystallisation of the residue, first from isopropyl acetate and then from ethanol gave 1,4-dihydro-2,6-dimethyl-4-(2-trifluoromethylphenyl)pyridine-3,5-dicarboxy lic acid bis-(2-hydroxyethyl) ester (4.6 g) m.p. 125.degree.-127.degree..

i. To a stirred solution of 1,4-dihydro-2,6-dimethyl-4-(2-trifluoromethylphenyl)pyridine-3,5 -dicarboxylic acid bis (2-benzyloxethyl)ester (18.2 g.) in dry dimethylformamide (100 ml) was added in portions, sodium hydride (1.38 g. of a 60% dispersion in oil). When the mixture had been stirred for a further 60 minutes at room temperature methyl iodide (30 ml) was added and stirring was continued for another hour. The reaction mixture was then treated with saturated ammonium chloride solution (150 ml) and the resulting solution extracted with ether. Evaporation of the dried extracts gave an oil which was purified by column chromatography to give as a pale yellow oil 1,4-dihydro-1,2,6-trimethyl-4-(2-trifluoromethylphenyl)pyridine-3,5-dicarb oxylic acid bis(2-benzyloxyethyl)ester (6.0 g).

ii. The bis-benzyl ether produced in (i) above (5.7 g) was hydrogenated over palladium-charcoal as described in Example 1 to give, after purification by column chromatography and recrystallisation from aqueous ethanol, 1,4-dihydro-1,2,6-trimethyl-4-(2-trifluoromethylphenyl)pyridine-3,5-dicarb oxylic acid bis (2-hydroxyethyl)ester (1.1 g) as colourless crystals m.p. 120.degree.-122.degree.C.

i. A mixture of acetoacetic ester (19.0 g) and 3-benzyloxy-2-propanol (32.0 g) were stirred under reflux for 2 hours. Fractional distillation under vacuum gave, as a colourless oil, acetoacetic acid (3-benzyloxy-2-propyl) ester (15.2 g), b.p. 130.degree.-135.degree.C/0.1 mm.

ii. A mixture of acetoacetic acid (3-benzyloxy-2-propyl) ester (23.8 g), o-trifluoromethylbenzaldehyde (8.7 g.) and concentrated ammonia (10.0 ml. of density 0.88) in ethanol (200 ml) was stirred under reflux for 24 hours and then poured into ice and water. The yellow oil which precipitated was separated and purified by column chromatography to give as a pale yellow oil 1,4-dihydro-2,6-dimethyl-4-(2-trifluoromethylphenyl)pyridine-3,5-dicarboxy lic acid bis(3-benzyloxy-2-propyl)ester (24.8 g).

iii. The bis-benzyl ether produced in (ii) above (10.6 g) was dissolved in ethanol and hydrogenated over palladiumcharcoal as described in Example 1 to give, after purification by column chromatography and crystallisation 1,4-dihydro-2,6-dimethyl-4-(2-trifluoromethylphenyl)pyridine-3,5-dicarboxy lic acid bis(3-hydroxy-2-propyl)ester.

Reaction of butyroacetic ester and 2-benzyloxyethanol by the procedure of Example 1(i) gives butyroacetic acid 2-benzyloxyethyl ester which, when used as the starting material in the process of Example 1(ii) gives the bis-benzyl ether of the title compound. Hydrogenolysis of this ether according to the procedure of Example 1(iii) yields the title compound.

Reaction of acetoacetic ester and 4-benzyloxybutanol according to the procedure of Example 1(i) gives acetoacetic acid 4-benzyloxybutyl ester which, when used as the starting material in the process of Example 1(ii) gives the bisbenzyl ether of the title compound. Hydrogenolysis of this ether by the procedure of Example 1(iii) yields the title compound.

The active ingredient is mixed with the sucrose and the resulting mixture is granulated with 10% gelatin solution. The granules are screened, dried and mixed with starch, talc and stearic acid, screened and compressed into a tablet.

The ingredients are mixed, screened and filled into a hard gelatin capsule.

The compositions prepared as in Examples 6 and 7 are administered orally to hypertensive subjects within the dose range given hereabove.