Scheme 1. Synthesis of 9.
Reagents and conditions: (a) ethyl acetoacetate, H2SO4, 25%; (b) BnBr, K2CO3, DMF, 85%; (c) SeO2, xylenes, 150 °C, 12h, 61%; (d) BnNH2, NaBH3CN, 50-80%; (e) BnBr, K2CO3, DMF, 100 °C, 90%; (f) DiBAlH, CH2Cl2, −78 °C, 72%.
Reagents and conditions: (a) ethyl acetoacetate, H2SO4, 25%; (b) BnBr, K2CO3, DMF, 85%; (c) SeO2, xylenes, 150 °C, 12h, 61%; (d) BnNH2, NaBH3CN, 50-80%; (e) BnBr, K2CO3, DMF, 100 °C, 90%; (f) DiBAlH, CH2Cl2, −78 °C, 72%.