Grisans

Another simplified nomenclature adopted here relates to natural spiro-2,3-dihydrobenzofuran derivatives, such as griseofulvin. The fundamental heterocycle, named grisan, being spirobenzofuran-2(3ff)-l -cyclohexane (5), griseofulvin (7-chloro-4,6,2 -trimethoxy-6 -methyl-spirobenzofuran-2(3//)-l -[2]cyclohexene-3,4 -dione) (6) becomes 7-chloro-4,6,2 -trimethoxy-6 -methyl-2 -grisene-3,4 -dione. 

Musetti, R., Olizzotto, R., Grisan, S., Martini, M., Borselli, S., Carraro, L. and Osier, R. (2007). Effects induced by fungal endophytes in Catharanthus roseus tissues infected by phytoplasmas. Bulletin of Insectology, 60 293-294. 

Although the distribution, persistence, and toxicity of these halogenated compounds — such as the chlorinated grisans, chloramphenicol, 7-chlorotetracycline, and clindamycin are antibiotics — are subject to the same principles as those outlined in this book, this aspect has seldom been examined. One exception that may serve as an illustration is the debromination of naturally occurring bromophenols by bacteria under anaerobic conditions (King 1988). 

A new chlorinated depsidone (maldoxone 120) and a new spirocyclohexadienone (maldoxin 121) have been isolated from the culture medium of an as yet unidentified Xylaria species. Their role in the grisan-depsidone biosynthetic pathway was discussed [147]. 

C1gHi Br2O6, D,L-Methyl 5,7-dibromo-2 a,5 a epoxy-4-methoxy-3-oxo-grisane-6 p-carboxylate, 42B, 471 C16H14O5, 9-Methylrubrofusarin, 43B, 768 CisHi Osf 2-Deacylusnic acid, 40B, 536 CisHieOa, Cunaniol acetate, 45B, 655... 

The situation is further confused by the widely-held belief that the biosynthetic pathway to the 14-carbon skeleton of griseofulvin should show features in common with that leading to the other members of the family of fungal grisans, geodin (II R = Cl, Rj = Me), erdin (II R = Cl, R = H) andbisdechlorogeodin (II R = H, Rj = Me) which possess a 15-carbon skeleton branched at an unusual position and where the pathway is, superficially, more complex. 

There is evidence (Rhodes et al, I96I) from the isolation of compounds (X) and (XII) that chlorination takes place at the benzophenone step of the P. patulum fermentation, and, indeed, is a key reaction in griseofulvin biosynthesis in shake culture. It may be noted however, that chlorination of a grisan intermediate apparently occurs in the biogenesis of geodin (Rhodes et aL, 1962). 

Grisans. HGl passed into a soln. of 1.4 g. rac-griseofulvin in abs. methanol 1.05 g. rac-isogriseofulvin, 2.0 g. dissolved in dioxane, 0.1 M Na-carbonate soln. added, and refluxed 15 min. 1.6 g. rac-griseofulvinic acid.—This two-stage procedure gives a better overall yield than the direct hydrolysis of rac-griseofulvin. A. Brossi et al., Helv. 43, 2071 (1960). 

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