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. Author manuscript; available in PMC: 2022 Apr 13.
Published in final edited form as: J Med Chem. 2020 Oct 29;63(21):12957–12977. doi: 10.1021/acs.jmedchem.0c01398

Scheme 1. General Synthesis of Compounds 5–13a.

Scheme 1.

aReagents and conditions: (i) copper sulfate, ascorbic acid, tert-butanol/water (54%); (ii) bis(triphenylphosphine) palladium (II) dichloride, copper iodide, triethylamine, tetrahydrofuran, 60 °C (84%); (iii) Raney nickel, hydrogen, methanol (89%); (iv) R-CO2H, propanephosphonic acid anhydride, pyridine (25–78%); (v) (a) trifluoroacetic acid, dichloromethane, (b) R-NH2, amide coupling reagent, solvent (15–98%).