Studien auf dem Gebiet der Naturstoffchemie, 89. Halogenierungsreaktionen des 1,3‐Dihydroxy‐10‐methyl‐9(10H)‐acridinons und seiner Ether — eine einfache regiospezifische Synthese des Acronycins

Abstract

Iodination of 1,3-dihydroxy-10-methyl-9-acridone (2c) and its ethers 2a and 2b gave the corresponding 2-iodo derivatives 3a -c. Bromination of 2a with NBS yielded 2-bromo-(lo), 4-bromo-( l l ) , as well as small amounts of 2,4-dibromo-l,3-dimethoxy-10-methyl-9-acridone (12). Under the same conditions from 2c 2-bromo-l,3-dihydroxy-1O-methyl-9-acridone (13) has been obtained. Chlorination of 2a with S02C12 in CHCI, gave-4-chloro-(14) and 2,4-dichloro-l-hydroxy-3-methoxy-10-methyl-9-acridone (15). The reaction of 3 b with copper(1) phenyl-and copper(1) isopropenylacetylide yielded the corresponding 2-substituted 4-methoxy-6-methylfuro[2,3-a]acridin-11(6ff)-ones 6a and 6b, respectively. From the condensation reaction of 3c with 3-chloro-3-methyl-1-butyne noracronycine (8) has been obtained.

Natural products chemistry. Part 124. Revised structure and synthesis of a new acridone alkaloid, hallacridone from Ruta graveolens tissue cultures

“…M.p., mixed m.p., i.r., 'H n.m.r., ms., and t.1.c. were identical with those recorded for the compound synthesized previously by heating the compound (4) in PEG 200 (see above).…”

“…experiment (irradiating at the N-Me signal) which would have resolved this problem. Therefore we decided to protect the C-2 of the acridone nucleus of compound (4) and then carry out the Claisen rearrangement in order to obtain It has been r e p ~r t e d , ~ that iodination of 1,3-dihydroxy-l0methylacridin-9( 10H)-one (3), and its mono-or di-methyl ethers, with IJHIO, in aqueous ethanol occurs at C-2 of the acridone nucleus. Compound (4) was successfully iodinated by this method to give ethyl 2-( l'-hydroxy-2'-iodo-9'-oxo-Treatment of compound (6) with pyridine and acetic anhydride at 100 "C yielded a complex mixture of products, from which ethyl 2-( 1 ',3'-diacetoxy-2'-iodo-9'-oxo-9',10'dihydroacridin-4'-ylmethyl)propenoate (7) and ethyl 2-( 1 ',3'diacetoxy-9'-oxo-9', 1 O'-dihydroacridin-4'-ylmethyl)propenoate (8) were isolated.…”

“…l P 1 ' A detailed biosynthetic pathway has been proposed for the origin of these furoacridones implicating rutacridone (16) as precursor. (4).-Ethyl bromomethacrylate (0.75 g) and anhydrous K,CO, (1.3 g) were added to a solution of 1,3-dihydroxy-lO-methylacridin-9( 10H)one (3) (0.625 g) in dry acetone (250 ml) and the mixture was heated under reflux for 2 h. It was then filtered and the solids were washed with dichloromethane. The combined filtrates were evaporated to dryness to give a yellow solid which on recrystallisation from CHC1,-MeOH yielded (4) 6), 169 (6), 154 (8), 140 (6), 128 (5), 115 (6), and 85 (6).…”