Reaction Steps
Sodium formate (0.040 g, 0.581 mmol) was added to a suspension of 2-amino-4-chloro-6-methyl-10,10-dioxo-10,11-dihydro-5-oxa-10lambda*6*-thia-dibenzo[a,d]cycloheptene-8-carboxylic acid isopropyl ester (0.23 g, 0.581 mmol) [prepared by hydrolysis of compound of Example 1 and followed by esterification using isopropanol/H2SO4] in formic acid (20 mL) and refluxed for 1.5 h. The reaction mixture was cooled and poured into ice water (100 mL). The solid precipitated was filtered, washed with water and dried. The crude product was crystallised with ethylacetate/pet. ether 60-80° C. to obtain the title compound. Yield: 0.12 g (48%); mp: 212-215° C.; 1H NMR (DMSO-d6, 300 MHz): δ 1.30 (d, 6H, OCH(CH3)2), 2.64 (s, 3H, CH3), 5.12 (m, 1H, OCH(CH3)2), 5.25 (s, 2H, CH2, trans minor isomer), 5.32 (s, 2H, CH2, cis major isomer), 7.33 (d, 1H, Ar, trans minor isomer), 7.50 (d, 1H, Ar, trans minor isomer), 7.69 (d, 1H, Ar, cis major isomer), 7.86 (d, 1H, Ar, cis major isomer), 8.10 (s, 1H, Ar), 8.15 (s, 1H, Ar), 8.30 (s, 1H, CHO, cis major isomer), 8.80 (d, 1H, CHO, trans minor isomer), 10.40 (d, 1H, NH, trans minor isomer), 10.57 (s, 1H, NH, cis major isomer); MS: m/e (ES−) 422 (M−1); analysis: C19H18ClNO6S requires C, 53.84,H, 4.28, N, 3.30, Cl, 8.36, S, 7.56; found: C, 54.27,H, 4.45, N, 2.94, Cl, 8.76, S, 7.77%.
