Reaction Steps
A mixture of (3S-trans)-4-amino-3,4-dihydro-3-hydroxy-2,2-dimethyl-2H-1-benzopyran-6-carbonitrile (0.65 g, 0.0030 mol, from example 1, part B) and [3-(1,2,4-oxadiazol-5-yl)]phenylcarbamic acid, 4-nitrophenyl ester (1.08 g, 0.0033 mol) in acetonitrile (25 mL) and dimethylformamide (20 mL) was stirred at 80° C. for one hour. The reaction mixture was concentrated in vacuo and the residue, diluted with ethyl acetate, was washed with 10% citric acid and water. The organic layer was dried over MgSO4 and concentrated in vacuo. The product was purified by flash chromatography (Sorbisol C 60 flash silica gel, 400 mL) and eluted with Hexane/EtOAc (2:1) and Hexane/EtOAc (1:1). The solvent was removed in vacuo, to give a solid that was triturated with anhydrous ether and dried in vacuo to yield 1.08 g of the title compound, m.p. 168°-170° C. TLC, silica gel, EtOAc/Hexane(2:l), Rf =0.42. 1H-NMR (DMSO-d6) δ9.1 (s, 1H), 9.0 (s, 1H), 8.5 (s, 1H), 7.5 (m, 4H), 7.0 (d, J=8.8 Hz 1H), 6.8 (d, J=8.8 Hz, 1H), 5.7 (d, J=5.9 Hz, 1H), 4.7 (t, J=8.8 Hz, 1H), 3.7 (dd, J=5.9 & 3.5 Hz, 1H), 3.4 (s, 1H), 1.5 (s, 3H), 1.2 (s, 3H); 13C-NMR (DMSO-d6) δ174.8, 158.6, 156.3, 155.7, 141.4, 132.6, 132.5, 130.0, 125.9, 123.7, 122.3, 120.6, 119.1, 117.9, 116.7, 102.7,l 80.4, 71.3, 49.5, 26.6, 18.9; IR (KBr) 2228, 1667, 1574, 1551, 1489 cm-1.M.S. (M+H)+ at 406, M.W. 405; [α]D =-55.20° (c=0.86 DMSO).
