Reaction Steps
A solution of 15b (90 mg, 0.16 mmol) in dichloromethane (2 mL) was cooled to −10° C. and treated with an excess of trifluoroacetic acid (10% v/v soln in dichloromethane, 2 mL). After 10 min at −10° C., the mixture was allowed to react at room temperature for 5 h. The solution was concentrated in vacuo and the residue crystallized from diethyl ether affording (+)-pinanediol (1R)-2-[3-carboxyphenyl]-1-(phenylmethanesulfonylamino)ethaneboronate (79 mg, 100% yield) as a cream coloured solid. Mp 155-158° C. [α]D+25.9 (c 0.6, CHCl3). 1H-NMR (400 MHz, CDCl3): δ 0.87 (3H, s, pinanyl CH3), 1.06 (1H, d, J 10.8, pinanyl Hendo), 1.31 (3H, s, pinanyl CH3), 1.33 (3H, s, pinanyl CH3), 1.88-2.38 (5H, m, pinanyl protons), 2.99 (1H, dd, J 13.7, 6.0, CHCH2), 3.15 (1H, dd, J 13.7, 5.6, CHCH2), 3.37 (1H, br, BCH), 4.31 (2H, s, CH2SO2), 4.40 (1H, d, J 7.7, CHOB), 4.51 (1H, br, SO2NH), 7.30-7.58 (7H, m, HArom), 7.97-8.01 (2H, m, HArom), 10.2 (1H, br, COOH). 13C-NMR (100 MHz, CDCl3): δ 24.0, 26.3, 27.0, 28.3, 35.0, 38.2, 38.5, 39.4, 42.4 (CB), 51.1, 59.2, 78.8, 87.3, 128.5, 128.6, 128.7, 127.2, 129.3, 129.4, 130.8, 131.2, 135.6, 139.0, 171.8. Anal. Calcd. for C26H32BNO6S: C, 62.78; H, 6.48; N, 2.82; S, 6.45. Found: C, 62.61; H, 6.72; N, 2.64; S, 6.21.
