First total syntheses of the 1,2,3,4-tetrahydronaphtho[2,1- f]isoquinolines annoretine and litebamine

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We describe here the first total synthesis of the two natural 1,2,3,4-tetrahydronaphtho[2,1- f]isoquinolines, annoretine and litebamine, from [2-(2-styrylphenyl)ethyl]methylcarbamic acid ethyl esters. The key steps were the Bischler–Napieralski cyclization to form the isoquinoline unit and photocyclization of the resulting 2-methyl-5-styryl-3,4-dihydro-2 H-isoquinolin-1-ones to 2-methyl-3,4-dihydro-2 H-naphtho[2,1- f]isoquinolin-1-ones.