Patent ID: 8242284

Claim:
A compound having the structural formula (1a) or (1b), a stereoisomer, tautomer, racemate or pharmaceutically acceptable salt thereof, Wherein: R1 is phenyl or benzyl, wherein the phenyl or benzyl is optionally substituted by 1, 2 or 3 substituents selected from —R a , —OR a , —SR a , —NR a R a , —CO 2 R a , —OC(═O)R a , —C(═O)NR a R a , —NR a C(═O)R a , —NR a S(═O)R a , —NR a S(═O) 2 R a , —C(═O)R a , —S(═O)R a , —S(═O) 2 R a , halogen, cyano, nitro and C 1-3 haloalkyl; and wherein the phenyl or benzyl is additionally substituted by 0, 1 or 2 substituents selected from C 1-6 alkyl, phenyl or benzyl; R2 is —(CH 2 ) m naphthyl; and R a is H, C 1-6 alkyl, C 1-3 haloalkyl, phenyl or benzyl; m is 0, 1, 2 or 3.