1: N-pentanoyl-N-[[2'-[N-(triphenylmethyl)tetrazol-5-yl]-1,1'-biphenyl-4-yl]methyl]amine With 2,6-dimethylpyridine; oxalyl dichloride in toluene T=0°C; 1 h; 2: ethyl 1-amino-1-cyclopentanecarboxylate in toluene T=0 - 20°C; 1 h;