A mixture of (7R,8aS)-N-(2-chloro-5-fluoropyrimidin-4-yl)-octahydro-5,5-dimethylindolizin-7-amine hydrochloride (775 mg, 2.31 mmol, 1.00 equiv), 1-(5-amino-2-(1-(tert-butyldimethylsilyloxy)-2-methylpropan-2-yloxy)phenyl)-4-methyl-1H-tetrazol-5(4H)-one (1.00 g, 2.54 mmol, 1.10 equiv), and PTSA monohydrate (880 mg, 4.62 mmol, 2.00 equiv) in IPA (80 mL) was heated to reflux for 3 d as monitored by LCMS. After the first day, in the morning, LCMS indicated a ratio of OTBS-protected product:product=1.5:1. Thus, more PTSA monohydrate (220 mg, 1.16 mmol, 0.50 equiv) was added and refluxing was continued. The reaction was checked by LCMS in the afternoon, which indicated a ratio of OTBS-protected product:product=1:1.2. Thus, more PTSA monohydrate (220 mg, 1.16 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=1:6.5. Thus, more PTSA monohydrate (220 mg, 1.16 mmol, 0.50 equiv) was added and refluxing was continued. The reaction was checked by LCMS in the afternoon, which indicated a ratio of OTBS-protected product:product=1:9. Thus, more PTSA monohydrate (220 mg, 1.16 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 1-(2-(1-hydroxy-2-methylpropan-2-yloxy)-5-(4-((7R,8aS)-octahydro-5,5-dimethylindolizin-7-ylamino)-5-fluoropyrimidin-2-ylamino)phenyl)-4-methyl-1H-tetrazol-5(4H)-one (compound 86) (870 mg, 70%) as a solid.
