Antibiotics, chromonics

Interest in the antibiotic bikaverin (531), a fungal metabolite with a benzo[Z>]xanthone skeleton, has culminated in its total synthesis (76JCS(Pl)499). The chromone moiety (530) was constructed as shown and the xanthone was obtained by cyclization of the acid chloride (Scheme 196). 

There is much interest in anthrapyran antibiotics. Synthesis of S-indomycinone indicates that a revision is required <07CEJ9939>. A total synthesis of racemic y-indomycinone 49 based on a Baker-Venkataraman rearrangement of the anthraquinone ester 47 and cyclisation of the resulting diketone to the chromone 48 has been reported <07EJ01905>. A total synthesis of the structurally simpler topopyrone C involves similar methodology <07TL1049>. In an alternative approach which is readily adaptable to the synthesis of other anthrapyrans, the... 

The side-chain of the antibiotic hedamycin contains two epoxy-groups, whose oxygen atoms have been shown by X-ray analysis to lie above one another a similar stereochemistry was detected in the diepoxide from the simpler chromone (155). The n.m.r. spectra of a wide selection of chromones (and some flavones) have been interpreted and used to distinguish between positional isomers. ... 

Budzisz et al. have described the synthesis and the antimicrobial properties of chromone derivatives (01APPMC381). These compounds were synthesized and tested for their antimicrobial activity against Gram-positive and Gramnegative bacteria using naHdixic acid as reference. (NaHdixic acid is one the first synthetic quinolone antibiotic.) The first cycHc phosphonic analogs of chromone 139 were obtained by the reaction of dimethyl 2-methyl- and dimethyl 2-phenyl-4-oxo-4H-chromen-3-ylphosphonate 138 with primary amines (99T4815) (Scheme 31). 

The ease of intercalation of other chro-monic and potentially chromonic materials. A number of biochemical reagents, such as acridines and ethidium bromide, intercalate readily between the stacked bases in DNA and RNA. Anticancer drugs, such as the square planar platinum complexes, intercalate avidly (Fig. 14) and naturally occurring antibiotics, such as actinomycin, similarly act by intercalation into the stack of bases [67]. They act as tailor-made spanners in the works and prevent the reading and replication of DNA. 

Many compounds of commercial interest, e.g., dyes, drugs, antibiotics, and anticancer agents, are either chromonic or have sufficiently chromonic character to be able to intercalate into chromonic systems. However, there is a distinction between commercially useful compounds, which incidentally happen to form liquid-crystalline phases, and compounds that have technological value specifically because of their mesogenic properties. 

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