Synthesis of spiro[isobenzofuran 1(3H),4' piperidines] as potential central nervous system agents

Article abstract of DOI:10.1021/jm00233a012

Synthesis of 1' methyl 3 phenylspiro[isobenzofuran 1(3H),4' piperidine] (7a, HP 365) and the demethyl analogue 9a (HP 505) was prompted by recognition of an aminoalkyl(aryl)isobenzofuran moiety common to the antidepressants talopram (Lu 3-010) and trans 10,11 dihydro 5,10 epoxy 5 [3 (methylamino)propyl] 5H dibenzo[a,d]cyclohepten 11 ol (MK-940). Convenient laboratory synthesis of 7a was provided by lithiation of 2 bromobenzhydryl methyl ether, followed by addition of 1 methyl 4 piperidone and acid catalyzed cyclization. N Dealkylation by standard methods afforded 9a. Synthesis of analogues was stimulated by discovery of marked inhibition of tetrabenazine induced ptosis for lead compounds 7a and 9a. Optimal antitetrabenazine activity is associated with the 3 phenylspiro[isobenzofuran 1(3H),4' piperidine] moiety where nitrogen is basic. Modification of this moiety by introduction of large nitrogen substituents or a C-3 substituent > H significantly reduced antitetrabenazine activity. A series of analogue with aromatic substituents was investigated; however, few of these compounds were significantly more active than 7a and 9a. Compound 9a was selected for additional studies.