322-35-0

Madopar,Roche,Italy,1974

Inhibitor (decarboxylase).

ChEBI: A carbohydrazide that results from the formal condensation of the carboxy group of DL-serine with the primary amino group of 4-(hydrazinylmethyl)benzene-1,2,3-triol. An aromatic-L-amino-acid decarboxylase nhibitor (DOPA decarboxylase inhibitor) that does not enter the central nervous system, it is used as its hydrochloride salt as an adjunct to levodopa in the treatment of parkinsonism. By preventing the conversion of levodopa to dopamine in the periphery, t causes an increase in the amount of levodopa reaching the central nervous system and so reduces the required dose. Benserazide has no antiparkinson actions when given alone.

35.5 grams of DL-seryl-hydrazide hydrochloride was dissolved in 350 ml of water and 35 grams of pyrogallolaldehyde (2,3,4-trihydroxy-benzaldehyde) added thereto at one time. In about 5-10 minutes a clear solution resulted, whereupon slow crystallization occurred and the temperature rose to about 6°-7°C. The crystallization was permitted to continue overnight at 5°C, and the very fine precipitate was then isolated by centrifugation and in the centrifuge washed with water, ethanol, and ether, yielding the dihydrate of DLseryl-( 2,3,4-trihydroxy-benzylidene) hydrazide hydrochloride, which melted at 134°-136°C and was poorly soluble in cold water, but very readily dissolved in hot water. The condensation was also effected in absolute ethanol yielding the anhydrous form of the hydrazone, which melted at 225°-228°C.
33.5 grams of the hydrazone-dihydrate was suspended in 330 ml of methanol and hydrogenated with 2.5 grams of palladium-carbon. After the absorption of 2.8 liters of hydrogen, the catalyst was filtered off and the solution evaporated in vacuo to a weight of about 52-55 grams. It was then immediately mixed with 160 ml of absolute ethanol and permitted to crystallize for 24 hours at room temperature and then for a further 24 hours at 0°C. The product was then filtered off with suction and washed with absolute ethanol and absolute ether. The so-obtained DL-seryl-(2,3,4-trihydroxy-benzyl)-hydrazide hydrochloride formed a white crystalline powder which was readily soluble in water and which melted at 146°-148°C.

Antiparkinsonian