Lanitop,Boehringer Mannheim,W. Germany,1972
Digoxin (10 g) is dissolved in a mixture of dimethylformamide (80 ml) and dioxane (80 ml) and then strontium hydroxide (3.5 g) and aluminum oxide (10 g, activity 1-2 according to Brockmann) are added. To this suspension methyl mesylate (9.3 g), dissolved in dioxane (80 ml) is added dropwise within one hour in the presence of an inert gas and under stirring. After the addition of the methylating agent is completed, the reaction mixture is stirred for further 5 hours, then chloroform (160 ml) is added, the precipitate is filtered off, washed with chloroform (100 ml), pyridine (40 ml) is added to the filtrate, which is then concentrated in vacuo to an oily residue. The latter is diluted with chloroform (300 ml) and extracted four times with distilled water (40 ml portions). The combined chloroform extracts are dried with anhydrous sodium sulfate and then concentrated in vacuo to a dry residue. Therefrom βmethyldigoxin is eluted on a SiO2 column with a chloroformlethanol mixture (93:7). After recrystallization from ethyl acetate, saturated with water, the yield of β-methyldigoxin is 6.7 g; MP 225°C to 229°C. IR spectrum is identical with the spectrum of standard methyldigoxin.
