A mixture of 4-((7R,8aS)-octahydro-5,5-dimethylindolizin-7-ylamino)-2-chloropyrimidine-5-carbonitrile hydrochloride (200 mg, 0.584 mmol, 1.00 equiv), 1-(5-amino-2-(1-(tert-butyldimethylsilyloxy)-2-methylpropan-2-yloxy)phenyl)-4-methyl-1H-tetrazol-5(4H)-one (255 mg, 0.643 mmol, 1.10 equiv), and PTSA monohydrate (225 mg, 1.17 mmol, 2.00 equiv) in IPA (20 mL) was heated at 70° C. overnight. After the first day, in the morning, LCMS indicated a ratio of OTBS-protected product:product=3:1. Thus, more PTSA monohydrate (56 mg, 0.292 mmol, 0.50 equiv) was added and temperature was raised to reflux. The reaction was checked by LCMS in the afternoon, which indicated a ratio of OTBS-protected product:product=1.5:1. Thus, more PTSA monohydrate (56 mg, 0.292 mmol, 0.50 equiv) was added and refluxing was continued. On the second day, in the morning, LCMS indicated a ratio of OTBS-protected product:product=1:4.5. Thus, more PTSA monohydrate (112 mg, 0.585 mmol, 1.00 equiv) was added and refluxing was continued. The reaction awas checked by LCMS in the afternoon, which indicated a ratio of OTBS-protected product:product=1:8. Thus, more PTSA monohydrate (56 mg, 0.292 mmol, 0.50 equiv) was added and refluxing was continued. On the third day, LCMS indicated the reaction was completed. After cooling to ambient temperature, the crude mixture was concentrated to dryness. The residue was taken in water, EtOAc, and aqueous 1N NaOH. The aqueous and organic layers were partitioned, and the aqueous layer was extracted with EtOAc 2×. The organic layer was dried (Na2SO4), filtered, and the solvent removed under vacuum. The crude product was purified by flash chromatography and eluted with DCM:2M NH3/MeOH=100:0 to 94:6 using 1% 2M NH3/MeOH increments to give compound 4-((7R,8aS)-octahydro-5,5-dimethylindolizin-7-ylamino)-2-(4-(1-hydroxy-2-methylpropan-2-yloxy)-3-(4,5-dihydro-4-methyl-5-oxotetrazol-1-yl)phenylamino)pyrimidine-5-carbonitrile (compound 83) (252 mg, 79%) as a solid.
