Methyl-4-[(2S,4R)-1-acetyl-4-amino-2-methyl-1,2,3,4-tetrahydro-6-quinolinyl]-3-methylbenzoate (for a preparation see Intermediate 96) (40 mg, 0.113 mmol) was dissolved in dichloromethane (DCM) (1.5 mL) and treated with copper(II) acetate (30.9 mg, 0.170 mmol) and triethylamine (0.047 mL, 0.340 mmol) The resulting mixture was stirred at room temperature for a few minutes then pyridine-3-boronic acid (41.9 mg, 0.340 mmol) was added. After 5 h, further boronic acid (3.5 mg, 0.028 mmol, 0.25 eq) was added and the mixture stirred at room temperature. The stirring was continued for 7 days with 10 additions of pyridine-3-boronic acid (41.9 mg, 0.340 mmol) at regular intervals (except on day 4 and day 5). The reaction mixture was then treated with a 3:1 water/ammonia 0.88 (1 mL), then was stirred for 10 min before being diluted with DCM (20 mL). The layers were separated and the organic phase was washed with a saturated NaHCO3 aqueous solution. The combined aqueous phases were extracted with DCM (20 mL). The combined organic phases were dried using a hydrophobic frit and then concentrated in vacuo. Purification of the residue on SP4 using a 10 G silica cartridge (gradient:50 to 100% AcOEt in Hexanes then 0 to 10% (2M NH3 in MeOH) in DCM) gave Methyl 4-[(2S,4R)-1-acetyl-2-methyl-4-(3-pyridinylamino)-1,2,3,4-tetrahydro-6-quinolinyl]-3-methylbenzoate (25 mg, 50%) as a yellow oil.
