Revista Cubana de Medicina Militar (Aug 2020)
A modified method for synthesis of amantadine hydrochloride
Abstract
Introduction: Amantadine hydrochloride (I) was well-known as an antiviral drug used to prevent and treat influenza A infections. Besides, it also was used to relieve the symptoms of Parkinson's disease in the early period. Several methods for the preparation of I have been reported. These procedures started with adamantane (II) in four or three reaction steps to produce amantadine hydrochloride with overall yields ranging from 45% to 58%. Objectives: Improving method for synthesis of amantadine hydrochloride could introduce to industrial scale. Methods: Step-by-step optimization to reduce the use of reagents, solvents, as well as the conditions of each step were screened to be milder and more environment-friendly. Results: All factors related to the yield of reaction to synthesize the intermediate and final compounds were screened to give the highest yield of each step. Finally, a two-step procedure for the synthesis of (I) from (II) via N-(1-adamantyl)formamide (III) with improving overall yield of 78% and a purity of 99.2% was established, and the structure of the product was confirmed by 1H-NMR,13C-NMR, IR and MS. The synthesis of N-(1-adamantyl)formamide (VI) from (II) also was successfully accomplished within only one step. This method avoided the use of liquid bromine or fuming sulfuric acid as reactants. The subsequent conversion of (VI) to (I) was carried out under milder reaction conditions without using hazardous solvents. Conclusions: An improved synthesis for amantadine hydrochloride (I) have been provided. This research can be an industrially convenient production of amantadine hydrochloride. Because the raw materials and reagents used in this research are cheap and available which also were screened to save their use. Moreover, the total preparation time was significantly reduced to save energy as well as labor.
