Substituted amide beta secretase inhibitors

A compound having the structural formula

• or a pharmaceutically acceptable salt thereof, wherein
• R2 is hydrogen or alkyl;
• R3 is phenylene;
• R4 is —C(O)-alkyl, —C(O)Oethyl, alkyl, cycloalkyl, cycloalkylalkyl, aryl, aralkyl, alkoxyalkyl, heterocyclyl, heterocyclylalkyl, heteroaralkyl or heteroaryl;
• R6 is
• each R7 is independently selected from hydrogen, —OH, alkyl, cycloalkyl, aryl, heteroaryl, aralkyl, heteroaralkyl, aralkoxy, heteroaralkoxy and alkoxy;
• and
• X is a bond connecting R3 and R4,
• or, alternatively, X is —O—, —S—, alkylene, -alkyleneNH—, -alkyleneNHC(O)—, -alkyleneNHSO2—, —NH—, —NHC(O)—, or —NHSO2—;
• wherein each alkyl is optionally substituted with 1 to 3 moieties selected from the group consisting of halo, alkyl, aryl, cycloalkyl, cyano, hydroxy, alkoxy, alkylthio, amino, —NH(alkyl), —NH(cycloalkyl), —N(alkyl)2, carboxy and —C(O)O-alkyl;
• and
• wherein each phenylene, heterocyclylalkyl, cycloalkyl, cycloalkylalkyl, aryl, heteroaryl, heterocyclyl, aralkyl, heteroaralkyl, aralkoxy or heteroaralkoxy is optionally substituted with 1 to 4 moieties selected from the group consisting of —CF3, alkyl, alkenyl, alkynyl, aryl, heteroaryl, aralkyl, alkylaryl, heteroaralkyl, arylalkenyl, heteroarylalkenyl, arylalkynyl, heteroarylalkynyl, alkylheteroaryl, hydroxy, hydroxyalkyl, alkoxy, aryloxy, aralkoxy, acyl, aroyl, halo, nitro, cyano, carboxy, alkoxycarbonyl, aryloxycarbonyl, aralkoxycarbonyl, alkylsulfonyl, arylsulfonyl, heteroarylsulfonyl, alkylthio, arylthio, heteroarylthio, aralkylthio, heteroaralkylthio, cycloalkyl, heterocyclyl, —C(═N—CN)—NH2, —C(═NH)—NH2, —C(═NH)—NH(alkyl), Y1Y2N—, Y1Y2NC(O)—, Y1Y2NSO2— and —SO2NY1Y2, wherein Y1 and Y2 can be the same or different and are independently selected from the group consisting of hydrogen, alkyl, aryl, cycloalkyl, —C(O)alkyl and aralkyl, with the proviso that cycloalkyl, cycloalkylene, heterocyclyl and heterocyclylene can be substituted with ═O,
• wherein:
• “heteroaryl” means a moiety selected from pyridyl, pyrazinyl, furanyl, thienyl, pyrimidinyl, isoxazolyl, isothiazolyl, oxazolyl, thiazolyl, pyrazolyl, furazanyl, pyrrolyl, pyrazolyl, triazolyl, 1,2,4-thiadiazolyl, pyrazinyl, pyridazinyl, quinoxatinyl, phthalazinyl, imidazo[1,2-a]pyridinyl, imidazo[2,1-b]thiazolyl, benzofurazanyl, indolyl, azaindolyl, benzimidazolyl, benzothienyl, quinolinyl, imidazolyl, thienopyridyl, quinazolinyl, thienopyrimidyl, pyrrolopyridyl, imidazopyridyl, isoquinolinyl, benzoazaindolyl, 1,2,4-triazinyl, and benzothiazolyl;
• and
• “heterocyclyl” (or “heterocycloalkyl”) means a moiety selected from piperidyl, pyrrolidinyl, pyrazolidinyl, imidazolinyl, piperazinyl, morpholinyl, thiomorpholinyl, dithianyl, trithianyl, thiazolidinyl, 1,3-dioxolanyl, 1,4-dioxanyl, tetrahydrofuranyl, tetrahydrothiophenyl, and tetrahydrothiopyranyl.