The synthesis of leniolisib starts with compound 1 as shown in Scheme 1 (Hoegenauer et al., 2016; Hoegenauer et al., 2017).
6-Benzyl-4-chloro-5,6,7,8-tetrahydro-pyrido[4,3-d]pyrimidine (compound 1) is coupled with (S)-tert-butyl 3-aminopyrrolidine-1-carboxylate (compound 2) in the presence of triethylamine at 120 °C for 42 h to give compound 3 a 93% yield. The benzyl group is deprotected with 20% palladium hydroxide on carbon and ammonium formate in methanol at 65 °C for 2 h to give compound 4 a 66% yield. Compound 4 is coupled with 5-bromo-2-methoxy-3-(trifluoromethyl)pyridine (compound 5) in the presence of sodium -tert-butoxide, tris(dibenzylideneacetone)dipalladium(0), 2-di-t-butylphosphino-2'-(N,N-dimethylamino)biphenyl in tert-butanol at 100 °C for 5 h to give compound 6 a 74% yield. Deprotection of the Boc group in DCM/TFA, followed by coupling with propionyl chloride in the presence of sodium bicarbonate in DCM at room temperature for 1 h gives the final compound 7 (leniolisib) a 76% yield.
