4-(2',4'-Difluorobiphenyl-4-yl)-2-methyl-4-oxobutanoic acid (1, flobufen) is subjected to clinical testing in the treatment of rheumatoid arthritis. Owing to the occurrence of a centre of chirality, the compound exists in two enantiomers, and its major human metabolite, viz. 4-(2',4'-difluorobiphenyl-4-yl)-4-hydroxy-2-methylbutanoic acid isolated in the lactone form (2), possesses two chiral centres, making possible the existence of four stereoisomers. All of the optical isomers of the substances 1 and 2 were prepared. For flobufen (1), the racemate was separated into the stereoisomers by using the salts 3 with R-(+)- or S-(-)-1-phenylethylamine. The pairs of stereoisomers of 2, obtained by reduction of R-(+)-flobufen or the S-(-)-enantiomer, were separated by column chromatography. The physico-chemical parameters of the optical isomers were determined and some biological activities were evaluated in both in vitro and in vivo models.
4-(2',4'-二氟联苯基-4-基)-2-甲基-4-氧代丁酸(1,氟布芬)正在临床试验中用于治疗类风湿性关节炎。由于存在手性中心,该化合物存在两种对映异构体,并且其主要的人体代谢产物,即以内酯形式分离的4-(2',4'-二氟联苯基-4-基)-4-羟基-2-甲基丁酸(2),具有两个手性中心,因此存在四种立体异构体的可能性。所有物质1和2的光学异构体均已制备。对于氟布芬(1),通过使用盐3和R-(+)-或S-(-)-1-苯乙胺将外消旋体分离成立体异构体。通过柱层析分离R-(+)-氟布芬或S-(-)-对映异构体还原得到的2的立体异构体对。确定了光学异构体的物理化学参数,并在体外和体内模型中评估了一些生物活性。