Poly cyclic aromatic hydrocarbons in Recent lake sediments—II. Compounds derived from biogenic precursors during early diagenesis

Occurrence and possible sources of perylene in marine sediments-a review☆

I. Spore Attachment and Invasion.- 1. Adhesion of Fungi to the Plant Surface: Prerequisite for Pathogenesis.- 2. Signaling for Infection Structure Formation in Fungi.- 3. The Plant Cell Wall as a Barrier to Fungal Invasion.- 4. Rust Basidiospore Germlings and Disease Initiation.- 5. Attachment of Mycopathogens to Cuticle: The Initial Event of Mycoses in Arthropod Hosts.- 6. The Fate of Fungal Spores in the Insect Gut.- 7. Candida Blastospore Adhesion, Association, and Invasion of the Gastrointestinal Tract of Vertebrates.- 8. Infectious Propagules of Dermatophytes.- II. Fungal Spore Products and Pathogenesis.- 9. Melanin Biosynthesis: Prerequisite for Successful Invasion of the Plant Host by Appressoria of Colletotrichum and Pyricularia.- 10. The Plant Cuticle: A Barrier to Be Overcome by Fungal Plant Pathogens.- 11. Appearance of Pathogen-Related Proteins in Plant Hosts: Relationships between Compatible and Incompatible Interactions.- 12. The Role of Cuticle-Degrading Enzymes in Fungal Pathogenesis in Insects.- 13. Potential for Penetration of Passive Barriers to Fungal Invasion in Humans.- 14. Dihydroxynaphthalene (DHN) Melanin and Its Relationship with Virulence in the Early Stages of Phaeohyphomycosis.- III. Host Response to Early Fungal Invasion.- 15. Invasion of Plants by Powdery Mildew Fungi, and Cellular Mechanisms of Resistance.- 16. Induced Systemic Resistance in Plants.- 17. The Plant Membrane and Its Response to Disease.- 18. The Fungal Spore: Reservoir of Allergens.- 19. Conidia of Coccidioides immitis: Their Significance in Disease Initiation.- 20. Cell-Mediated Host Response to Fungal Aggression.- 21. Suppression of Phagocytic Cell Responses by Conidia and Conidial Products of Aspergillus fumigatus.- IV. Molecular Aspects of Disease Initiation.- 22. Molecular Approaches to the Analysis of Pathogenicity Genes from Fungi Causing Plant Disease.- 23. Current Status of the Molecular Basis of Candida Pathogenicity.- Taxonomic Index.

The Fungal spore and disease initiation in plants and animals

Many fungi, lichens, and bacteria produce xanthones (derivatives of 9H-xanthen-9-one, “xanthone” from the Greek “xanthos”, for “yellow”) as secondary metabolites. Xanthones are typically polysubstituted and occur as either fully aromatized, dihydro-, tetrahydro-, or, more rarely, hexahydro-derivatives. This family of compounds appeals to medicinal chemists because of their pronounced biological activity within a notably broad spectrum of disease states, a result of their interaction with a correspondingly diverse range of target biomolecules. This has led to the description of xanthones as “privileged structures”.(1) Historically, the total synthesis of the natural products has mostly been limited to fully aromatized targets. Syntheses of the more challenging partially saturated xanthones have less frequently been reported, although the development in recent times of novel and reliable methods for the construction of the (polysubstituted) unsaturated xanthone core holds promise for future endeavors. In particular, the fascinating structural and biological properties of xanthone dimers and heterodimers may excite the synthetic or natural product chemist.

Xanthones from Fungi, Lichens, and Bacteria: The Natural Products and Their Synthesis

Xanthones from fungi, lichens, and bacteria : the natural products and their synthesis

The structure suggested for cercosporin, a naturally occurring dihydroxy-perylenequinone, is unusual in having a methylenedioxy-group present in a seven-membered ring bridging a biphenyl system.

The structure of cercosporin, a naturally occurring quinone

The constitutions of the pigments produced by moulds of the genus Elsinoe, the elsinochromes A, B, and C, have been elucidated. The stereochemistry of elsinochrome A has been established.

Pigments of Elsinoe species. Part II. Structure of elsinochromes A, B, and C

A further pigment produced by the mould Elsinoe annonae has been isolated. This compound, elsinochrome D (IV), the structure of which has been elucidated, is unusual in being a monoether of a peri-dihydroxy-quinone.

Pigments of Elsinoe species. Part V. The structure of elsinochrome D

The structures assigned to elsinochrome A and its two isomeric dimethyl ethers have been confirmed by the use of special techniques of magnetic resonance spectroscopy. Nuclear Overhauser effects involving methoxy-groups and adjacent aromatic protons have been observed; signals from such methoxy-groups show larger half-line-widths in the unperturbed n.m.r. spectra than do those of groups without free ortho-positions. These observations should be helpful in structure elucidations.

Pigments of Elsinoe species. Part IV. Confirmatory evidence for the structure of elsinochrome A and its ethers from studies of nuclear magnetic resonance (solvent and overhauser effects) and electron spin resonance

The formation of the two isomeric dimethyl ethers of elsinochrome A takes place via the respective monomethyl ethers; compounds of the latter type have hitherto been observed only rarely.

R. J. J. Ch. Lousberg

Papers

The structure of cercosporin, a naturally occurring quinone

Pigments of Elsinoe species. Part II. Structure of elsinochromes A, B, and C

Pigments of Elsinoe species. Part V. The structure of elsinochrome D

Pigments of Elsinoe species. Part IV. Confirmatory evidence for the structure of elsinochrome A and its ethers from studies of nuclear magnetic resonance (solvent and overhauser effects) and electron spin resonance

Pigments of Elsinoe species. Part III. Methylation of elsinochrome A. Formation of mono- and di-methyl ethers