Practical, enantiomeric synthesis of a 7-[3-(4-fluoro-piperidin-1-yl)-propoxy]-2-methyl-4-(4-methylsulfanyl-phenyl)-1,2,3,4-tetrahydro-isoquinoline as a dual serotonin transporter/histamine H3 ligand

ORGN 113

Xiaohu Deng, Jimmy T. Liang, JLiang4@PRDUS.JNJ.COM, Jing Liu, Heather McAllister, Carsten Schubert, and Neelakandha S. Mani. Johnson & Johnson Pharmaceutical Research Institute, 3210 Merryfield Row, San Diego, CA 92121
A series of dual SSRI/Histamine H3 antagonists were designed with the expectation that an SSRI with histamine H3 activity may improve efficacy for the treatment of depression. These compounds, featuring a tetrahydroisoquinoline core structure tethered with an H3 pharmacophore side chain, showed high affinity for the histamine H3 receptor and serotonin reuptake transporter (SERT). One compound, a 7-alkoxy-4-aryl-tetrahydroisoquinoline structure, exhibited promising properties. A practical enantiomeric synthesis of 7-[3-(4-fluoro-piperidin-1-yl)-propoxy]-2-methyl-4-(4-methylsulfanyl-phenyl)-1,2,3,4-tetrahydro-isoquinoline has been developed. This route features a novel sequential Friedel-Crafts reaction strategy to construct the 4-aryl-tetrahydroisoquinoline core. In addition, a resolution utilizing di-p-toluoyl-tartaric acid was successfully performed on an advanced intermediate to provide enantiomerically pure material. Overall, our route is concise and amenable for large-scale synthesis.