Natural product chemisrty, 143. Convenient synthesis of isoacronycine and some other new acridone derivatives
The iodination of 1,3-dihydroxy-9-acridone (1), 1-hydroxy-3-methoxy-10-methyl-9-acridone (2) and 1,3-dihydroxy-10-methyl-9-acridone (3) yields 1,3-dihydroxy-2,4-diiodo-9-acridone (4), 1-hydroxy-2-iodo-3-methoxy-10-methyl-9-acridone (5) and 1,3-dihydroxy-2-iodo-10-methyl-9-acridone (6), respectively. The methylation of 4 and 5 gives 2,4-diiodo-1,3-dimethoxy-10-methyl-9-acridone (7) and 2-iodo-1,3-dimethoxy-10-methyl-9-acridone (9), respectively. The direct CC coupling of 2-methyl-3-buten-2-ol to the compounds 5, 7 and 9 by palladium catalysed Heck condensation method gives three new acridone derivatives 1-hydroxy-2-(3-hydroxy-3-methyl-1-butenyl)-3-methoxy-10-methyl-9-acridone (10), 2,4-bis(3-hydroxy-3-methyl-1-butenyl)-1,3-dimethoxy-10-methyl-9-acridone (12) and 2-(3-hydroxy-3-methyl-1-butenyl)-1,3-dimethoxy-10-methyl-9-acridone (13) while compound 6 is converted into isonoracronycine (11). The methylation of 11 yields isoacronycine (14).