Acridone alkaloids dimeric

The first acridone alkaloid dimers with a C—C junction, the semisynthetic dimers AB-1 and AB-2, were reported in 1985 [6]. AB-1 is a dimer with two noracronycine units and AB-2 was constructed with a noracrony-cine and an isonoracronycine unit. 

Acridone alkaloids comprise a relatively small group of alkaloids that are found solely in some Rutaceae genera. Some 100 examples of this alkaloid group have been isolated and these include the monomeric acridones and the acridone-coumarin dimers (acrimarines) isolated from Citrus plants some binary alkaloids have recently been isolated and described (Takamura et al, 1995). 

A considerable number of new quinoline and acridone alkaloids has been identified and the recognition of two new groups of dimeric quinolinone alkaloids is of particular interest. There has been little activity in the quinazoline alkaloid area and this section is omitted this year. 

The report of these semisynthetic derivatives preceded the report of the isolation of glycobismine A, the first naturally occurring bis-acridone alkaloid isolated from the bark and root bark of Glycosmis citrifolia collected in Taiwan [7]. Oligomers of noracronycine and related alkaloid derivatives, dimers and trimers, tetramers, and pentamers were also reported [8], and these oligomers and the chemical reactions concerning acronycine and related compounds were reviewed [9,10]. 

Table 24.17 Occurrence of dimeric acridone alkaloids in Rutaceae species...

No data is available on the biosynthesis of dimeric acridone alkaloids, which have been found in Rutaceae. Acridone-coumarin/xanthone/Ugnin dimers have also been found in Rutaceae (Table 24.17). The bark of the New Caledonia tree Sarcomelicope megistophylla (Rutaceae) have yielded an intriguing range of... 

In terms of organization, biosynthetic considerations take precedence. These are followed by a description of the various groiqrs of naturally occurririg acridone alkaloids the simple aoidones, C-prenylacridones, futoacridones, pyranoacridones, and finally the dimeric acridone all oids and related compounds. 

Tables II, HI, IV and V survey the structures, properties and the distribution of naturally occurring C-prenylacridones, furanoacridones, pyranoacridones and dimeric acridone alkaloids, respectively.

None of the naturally occurring dimeric acridone alkaloids containing a carbon-carbon linkage have been synthesized to date. Nevertheless, glycobismine-A (184), and the diastereoisomeric glycobismines-B and C, both represented by structure 187, should be considered to arise most probably by acid-catalyzed condensation between the two corresponding monomeric acridone units. 

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