... Heterocyclic Chem., 28, 379 (1991). ... obtained with the 2-nitrobenzoyl derivative 6d; compound 9d was obtained in high yield, the protecting group stabilized it enough to allow chemical modifications like ... 2H(H-3+H-4) 8.58 m 7.92 8.67 2H(H-8+H-9) m 11.8 NH.s 11.6 NH, s - J 1,2 ...