The simple synthesis of antimycotic alkaloid tryptanthrin 17 via the quina-zolinone annelation is summarized also in Scheme 18. Quinazolinone annela-tion of commercially available isatin 84 under the shown conditions gave 17 in 43% overall yield (Scheme 18) [222]. As the second route, oxindole 82 was annelated to indolo[2,1-fr]quinazolin-12(6ff)-one 83, which could be converted to 17 by air-oxidation but only in the modest yield [222]. Recently an efficient procedure for synthesis 17, 16 and luotonin A (26), etc. has been reported using cyclocondensation of iminochloride and methylanthranylate, followed by further manipulations by Jahng et al. [229]. Several known attractive routes to 17 involves cyclocondensation of isatin with isatoic anhydride by Mitscher et al. [230], (Ru)3(CO)12-catalyzed reductive N-heterocyclization by Watanabe et al. [182,223].

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