1.3- Dihydroxy-5-methoxy-9-acridone

Hydroxynoracronycine (40) is a constituent of Atalantia ceylonica and a metabolite of the antitumour compound acronycine its synthesis has been reported (Scheme 6).31 The reaction of l,3-dihydroxy-5-methoxy-9-acridone (36) with 3-chloro-3-methylbut-l-yne and cyclization in situ of the products furnished the chromenes (38) and (39) the formation of the intermediate (37) involves C-alkylation with the chlorobutyne, a reaction encountered previously during the synthesis of flindersine.32 Chromene (39) was converted into 11-hydroxy-noracronycine by successive methylation and demethylation. 

Reisch et al. (93JHC981) described two different methods for the synthesis of 4-azaacronycine 71. One method involves the fusion of 1,3-dihydroxy-10-methyl-9(10//)-acridone 69 with 3-amino-3-methylbut-l-yne in the presence of CuCb in a closed ampule, followed by methylation (Scheme 13). The second method involves the A-alkylation of 3-amino-l-methoxy-lO-methyl-9(107/)-acridone 70 with 3-chloro-3-methylbut-l-yne, followed by in situ cyclization (Scheme 13). 

Trihydroxy-4-methoxy-10-metbyl-2,8-f>/i(3-metbylbut-2-enyl) acridin-9(10/f)-one, l,5-dihydroxy-2,3-dimetboxy-10-metbyl-9-acridone, 2,3-Dihydro-4,9-dihydroxy-2-(2-bydroxypropan-2-yl)-I I-methoxy-10-methylfuro[3,2-b]acridin-5(10/7)-one, 3,4-Dibydro-3,5,8-trihydroxy-6-methoxy-2,2,7-trimethyl-2//-pyrano[2,3-a]acridin-12(7/7)-one, 2-(3,4-methylenedioxyphenyletbyl)quinoline, 2-n-nonylquinolin-4(l/f)-one, 2-nonylquinolin-4-ol V-oxide, 2-[(lE)-undec-... 

Alkaloids considered in this section derive biogenetically from 1,3-dihydroxy-lO-methylacridone (19) and 1,3-dihydroxyacridone (22) by simple deoxygenation and/or oxidation of the acridone aromatic skeleton. Subsequent O-alkylation very often takes place, and most natural acridones bear methoxy or methylenedioxy substituents. A few, exemplified by vebilocine (27) (94), evoprenine (28) (95), and 3-graanyloxy-l-hydroxy-4-methoxy-10-methylacridone (29) (96), are also substituted by prenyloxy or geranyloxy groups. 

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