A condensation-cyclization reaction of a 4-[N-alkyl-N-(tert-butyloxycarbonyl)amino]phenylacetic acid (12a-b) with 2-bromo-4-(methylsulphonyl)acetophenone (6) in the presence of triethylamine and 1,8-diazabicyclo[5.4.0]undec- 7-ene afforded 4-[4-(methanesulphonyl)phenyl]-3-[4-(N-alkyl-N-tert-butyloxy carbonyl)amino)phenyl]-5H-furan-2- ones (13a-b) which upon reaction with HCl–saturated methanol gave non-protected furanones 14a-b. Subsequent reaction of the furanone 14a with nitric oxide (40 psi) proceeded via a N-methylamino-N-diazen-1-ium-1,2-diolate intermediate that undergoes protonation of the more basic diazen-1-ium-1,2-diolate N2-nitrogen and then loss of a nitroxyl (HNO) species to furnish the N-nitroso product 15.
