ls with permission denied

My user belongs to developer group as soon as the user called tomcat. When I do ls -la /opt/tomcat/latest it gives me

total 160 drwxrwxr-x 11 tomcat developer  4096 mai 14 14:41 . drwxr-xr-x  3 tomcat developer  4096 mai 13 14:07 .. drwxrwxr-x  2 tomcat developer  4096 mai 14 14:41 backup drwxrwx---  2 tomcat developer  4096 mai 13 14:03 bin -rw-rw----  1 tomcat developer 19182 abr 12 11:26 BUILDING.txt drwxrwx---  3 tomcat developer  4096 mai 14 14:02 conf -rw-rw----  1 tomcat developer  5407 abr 12 11:26 CONTRIBUTING.md drwxrwx---  2 tomcat developer  4096 mai 13 14:03 lib -rw-rw----  1 tomcat developer 57092 abr 12 11:26 LICENSE drwxrwx---  2 tomcat developer  4096 mai 15 10:20 logs -rw-rw----  1 tomcat developer  2333 abr 12 11:26 NOTICE -rw-rw----  1 tomcat developer  3255 abr 12 11:26 README.md -rw-rw----  1 tomcat developer  6852 abr 12 11:26 RELEASE-NOTES -rw-rw----  1 tomcat developer 16262 abr 12 11:26 RUNNING.txt drwxrwx---  2 tomcat developer  4096 mai 15 12:10 temp drwxrwx---  8 tomcat developer  4096 mai 13 15:08 webapps drwxrwx---  3 tomcat developer  4096 mai 13 14:12 work drwxrwxr-x  4 tomcat developer  4096 mai 14 14:41 wtpwebapps 

But when I do ls -la /opt/tomcat/latest/conf it gives me permission denied. Any idea about what is happening?