A stirred suspension of 2'-methyl-4'-(5-methyl-1,3,4-oxadiazol-2-yl)biphenyl-4-carboxylic acid (D11, 0.53 g, 1.8 mmole) in thionyl chloride (8 ml) was heated at about 45° C. for 30 minutes, then concentrated in vacuo. The yellow solid was dissolved in THF (10 ml)/dichloromethane (5 ml) and added to a stirred solution of 1'-ethyl-2,3,6,7-tetrahydrospiro[furo[2,3-f]indole-3,4'-piperidine] (D109, 0.46 g, 1.8 mmole) and triethylamine (0.50 ml, 3.6 mmole) in THF (15 ml) at 5° C. under argon. The solution was stirred at room temp. for 2 h, then concentrated in vacuo. The residue was treated with 10% Na2CO3 solution and extracted with ethyl acetate. The extract was dried (Na2SO4), concentrated in vacuo and the residue chromatographed on silica gel eluting with 3% methanol/chloroform and the yellow oil obtained passed through a short basic alumina column eluting with ethyl acetate to afford the title compound as a beige foam (0.62 g, 68%). This was converted to its hydrochloride (mp 269-273° C.) and mesylate (mp 275-279° C.) salts.
