A compound of structural formula I: or pharmaceutically acceptable salts and individual enantiomers and diastereomers thereof wherein: W and Z independently are absent or represent C(R 2) 2, -O-, NR 2, CO, or SO 0-2; R 2 represents H, C 1-6 alkyl, CF 3, OH, CHF 2, or CH 2 F; R 3 is CHR 4 R 5 wherein one of R 4 and R 5 is C 1-6 alkyl or hydrogen and the other is (CH 2) n phenyl, (CH 2) n pyridyl, (CH 2) n pyrimidyl, (CH 2) n triazolyl, pyrazinyl or (CH 2) n oxadiazolyl, said phenyl, pyridyl, pyrimidyl, triazolyl, pyrazinyl or oxadiazolyl optionally substituted with 1 to 3 groups of R a; R 6 represents hydrogen, OR 2, CF 3, C(R 2) 2 OR 2, C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, said alkyl being optionally substituted with 1 to 3 groups of R a'; R 7 is represented by structural formula Ia: wherein X is N or CH; and R 1 represents H, C 1-6 alkyl, halogen, (CH 2) n CF 3, C 3-10 cycloalkyl, C(R 2) 2 OH, -O-, CN, (CH 2) n OR 2, (CH 2) n C 5-10 heterocyclyl, (CH 2) n C 6-10 aryl, or C 1-6 alkoxy; said alkyl, cycloalkyl, heterocyclyl and aryl optionally substituted with 1 to 3 groups of C 1-6 alkyl, halogen, hydroxyl, (CH 2) n CF 3, or CN; R a represents C 1-6 alkyl, halogen, hydroxyl, OR 2 (CH 2) n CF 3, C 3-6 cycloalkyl, NR 2 C R 2, C N(R 2) 2, C(R 2) 2 OR 2, C R 2, NO 2, CN, N(R 2) 2, C OR 2, SO 2 R 2, OR 2, (CH 2) n C 5-10 heterocyclyl, or (CH 2) n C 6-10 aryl, said heterocyclyl and aryl optionally substituted with 1 to 3 groups of C 1-6 alkyl, halogen, hydroxyl, (CH 2) n CF 3,or CN; R a' is C 1-6 alkyl, halogen, hydroxyl, OR 2 (CH 2) n CF 3, NR 2 C R 2, C N(R 2) 2, C(R 2) 2 OR 2, C R 2, NO 2, CN, N(R 2) 2, C OR 2, SO 2 R 2, or OR 2; and n represents 0 to 4, provided that WZR 6 is not hydrogen. W and Z independently are absent or represent C(R 2) 2, -O-, NR 2, CO, or SO 0-2; R 2 represents H, C 1-6 alkyl, CF 3, OH, CHF 2, or CH 2 F; R 3 is CHR 4 R 5 wherein one of R 4 and R 5 is C 1-6 alkyl or hydrogen and the other is (CH 2) n phenyl, (CH 2) n pyridyl, (CH 2) n pyrimidyl, (CH 2) n triazolyl, pyrazinyl or (CH 2) n oxadiazolyl, said phenyl, pyridyl, pyrimidyl, triazolyl, pyrazinyl or oxadiazolyl optionally substituted with 1 to 3 groups of R a; R 6 represents hydrogen, OR 2, CF 3, C(R 2) 2 OR 2, C 1-6 alkyl, C 2-6 alkenyl, C 2-6 alkynyl, said alkyl being optionally substituted with 1 to 3 groups of R a'; R 7 is represented by structural formula Ia: wherein X is N or CH; and R 1 represents H, C 1-6 alkyl, halogen, (CH 2) n CF 3, C 3-10 cycloalkyl, C(R 2) 2 OH, -O-, CN, (CH 2) n OR 2, (CH 2) n C 5-10 heterocyclyl, (CH 2) n C 6-10 aryl, or C 1-6 alkoxy; said alkyl, cycloalkyl, heterocyclyl and aryl optionally substituted with 1 to 3 groups of C 1-6 alkyl, halogen, hydroxyl, (CH 2) n CF 3, or CN; R a represents C 1-6 alkyl, halogen, hydroxyl, OR 2 (CH 2) n CF 3, C 3-6 cycloalkyl, NR 2 C R 2, C N(R 2) 2, C(R 2) 2 OR 2, C R 2, NO 2, CN, N(R 2) 2, C OR 2, SO 2 R 2, OR 2, (CH 2) n C 5-10 heterocyclyl, or (CH 2) n C 6-10 aryl, said heterocyclyl and aryl optionally substituted with 1 to 3 groups of C 1-6 alkyl, halogen, hydroxyl, (CH 2) n CF 3,or CN; R a' is C 1-6 alkyl, halogen, hydroxyl, OR 2 (CH 2) n CF 3, NR 2 C R 2, C N(R 2) 2, C(R 2) 2 OR 2, C R 2, NO 2, CN, N(R 2) 2, C OR 2, SO 2 R 2, or OR 2; and n represents 0 to 4, provided that WZR 6 is not hydrogen.