The present invention relates to a compound of formula (I) including any stereochemically isomeric form thereof, or a pharmaceutically acceptable salt thereof, wherein R1 is -C(=O)O-alkyl, carbonate ester, or -C(=O)-alkyl, ester, or -C(=O)N-alkyl, carbamate ester and wherein R2 is -CH3 or -CD3. The alkyl ester can contain saturated or unsaturated C12 to C26 alkyl carbon. The alkyl carbon chain can have either a straight, branched, noncyclic, cyclic, unsubstituted or substituted structure.本發明提供式(I)化合物，包括其立體異構體及藥學上可接受的鹽。其中R1系選自-C(=O)O-烷基、碳酸酯、-C(=O)-烷基、酯、-C(=O)N-烷基、氨基甲酸酯；其中R2系選自-CH3或-CD3。烷基酯包括飽和和不飽和的C12到C26烷基碳，烷基碳鏈可以是直鏈或支鏈、非環狀或環狀、未經取代的或經取代的結構。
