Method 3: General conditions for deprotection of N-Boc carbamates in the presence of borate esters: 1,2,3,6-tetrahydro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine was dissolved in tert-butylmethyl ether (0.4 M final ester concentration), then HCl (g) was drummed into the solution over a period of 15 min. The reaction mixture was stirred at room temperature for 1 h. Subsequent removal of the solvent under a stream of nitrogen afforded 1,2,3,6-tetrahydropyridine-4-boronic acid pinacol ester hydrochloride as a white solid in quantitative yield. Example 2: Tetrahydropyridine-4-boronic acid pinacol ester was prepared in a 3-step reaction using Method 3 starting from the deprotection of 1,2,3,6-tetrahydro-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine. The resulting HCl amine salt was dissolved in dichloromethane (0.2 M) and benzyl chloroformate (1.2 eq.) and triethylamine (3.0 eq.) were added sequentially. The reaction mixture was stirred at room temperature for 2 hours before being diluted with 1N HCl and extracted with excess dichloromethane. The organic layer was dried over MgSO4 and concentrated to afford the target carbamate in quantitative yield, which was subsequently converted directly to the boronic acid derivative via Method 2. [M-H]? = 260.1 m/z. Activity: B
