4-(9>-cyclopentyl-5'-methyl-6>-oxo-5>,6>,8>,9>- tetrahydrospiro[cyclobutane-l,7'-pyrimido[4,5-b][l,4]diazepine]-2'-ylamino)-3- methoxybenzoic acid; [0521] Ethyl 1-cyanocyclobutanecarboxylate; To a solution of sodium ethoxide (21wt% in EtOH, 5.79 rnL, 15.5 mmol) in EtOH (25 mL), was added ethyl cyanoacetate(1.12 mL, 10.5 mmol), followed shortly thereafter by 1,1-dibromopropane (1.12 mL, 10 mmol). The reaction mixture was refluxed for 3 hrs. It was then concentrated, and diluted to ethyl acetate. The organic layer was washed with NaHCCh, brine, water, dried over Na2SO4 and concentrated in vacuo to obtain ethyl 1-cyanocyclobutanecarboxylate (1.17 g, 74% yield) as a red liquid. It was used directly for next step reaction.
