Hydrochloric Acid → N-(6-Cyano-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-4-yl)-a-hydroxybenzeneacetamide

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To a solution of R-(-)-mandelic acid (22.1 g, 0.14 mole) and 1-hydroxybenzotriazole hydrate (19.6 g, 0.14 mole) cooled to 0° C. was added successively N-methylmorpholine (16.2 g, 0.16 mole), 4-amino-6-cyano-3,4-dihydro-2,2-dimethyl-2H-1-benzopyran (29.4 g, 0.14 mole, Example 8, part D) and 1-(3-dimethylaminopropyl)-2-ethylcarbodiimide.HCl (27.9 g, 0.14 mole). The reaction mixture was stirred 0.5 hours at 0° C. and two hours at room temperature. The solvent was recovered under vacuum and the residue was partitioned between 5% aqueous HCl and ethyl acetate. The organic fraction was washed with saturated sodium bicarbonate solution, saturated sodium chloride solution, dried over magnesium sulfate and evaporated in vacuo to obtain 52 g of yellow gum. The crude diastereomer mixture was chromatographed on silica eluting with 1:1 hexane/ethyl acetate to obtain 23.2 g (47.7%) of Isomer A. m.p.=120°-121° C., [a]D25 =-39.5°. 1H NMR (CDCl3) δ7.43-7.34 (m, 7H), 6.81 (d, J=8.20 Hz, 2H), 5.23 (m, 1H), 5.13 (d, J=3.52 Hz, 1H), 4.27 (m, 1H), 2.08 (dd, J=5.86 and 13.78 Hz, 1H), 1.71 (d, J=12.31 Hz, 1H), 1.42 (s, 3H), 1.36 (s, 3H). 13C NMR (CDCl3) δ173.26, 158.09, 139.60, 133.30, 132.46, 129.27, 129.18, 126.88, 123.39, 119.62, 118.99, 103.64, 77.00, 74.50, 42.33, 39.59, 29.77, 25.05. MS: (M+H)+ @337.

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