Robert Velten

Determination of the absolute configuration of a tetracyclic drimane sesquiterpenoid by Mosher's method

Abstract The high field NMR application of the Mosher method has been successfully applied to determine the absolute configuration of a tetracyclic dihydroxydrimane derivative. The result indicates that highly functionalized drimanes from basidiomycetes correspond in their stereochemistry to (−)-drimenol.

KUEHNEROMYCINS A AND B, TWO NEW BIOLOGICAL ACTIVE COMPOUNDS FROM A TASMANIAN KUEHNEROMYCES SP. (STROPHARIACEAE, BASIDIOMYCETES)

Abstract In a search for new inhibitors of RNA-directed DNA-polymerases kuehneromycin A (1) was isolated from fermentations of a Tasmanian Kuehneromyces species. Its structure was elucidated by spectroscopic methods. Kuehneromycin A (1) is a non-competitive inhibitor of avian myeloblastosis virus (Ki 200 μᴍ) and moloney murine leukemia virus (Ki 40 μᴍ) reverse transcriptases. The second compound, kuehneromycin B (2) is a strong inhibitor of platelet aggregation stimulated with different inducers. In addition, both compounds exhibit cytotoxic and antimicrobial activities.

Hyphodontal, a New Antifungal Inhibitor of Reverse Transcriptases from Hyphodontia sp. (Corticiaceae, Basidiomycetes)

Abstract In a search for inhibitors of RNA-directed DNA polymerases a new isolactarane sesquiterpenoid, hyphodontal (1), was isolated from fermentations of a Canadian Hyphodontia species. Its structure was elucidated by spectroscopic methods. Hyphodontal strongly inhibits the growth of several yeasts and is a non-competitive inhibitor of avian myeloblastosis virus (Ki 346 μᴍ) and Moloney murine leukemia virus (Ki 112 μᴍ) reverse transcriptases. In addition, cytotoxic and antifungal activities were observed.

Podoscyphic Acid, A New Inhibitor Of Avian Myeloblastosis Virus And Moloney Murine Leukemia Virus Reverse Transcriptase From A Podoscypha Species [1]

A novel enzyme inhibitor of RNA -directed DNA -polym erases of avian myeloblastosis and murine leukemia virus was isolated from fermentations of an tasmanian Podoscypha species. Its structure was elucidated by spectroscopic methods and oxidative degradation as (E)-4,5- dioxo-2-hexadecenoic acid (1). The enzyme inhibitor, which was named podoscyphic acid, did not inhibit DNA and RNA synthesis in permeabilized L 1210 cells nor did it affect RNA synthesis in isolated nuclei of L 1210 cells. 1 inhibits protein synthesis in whole L 1210 cells and rabbit reticulocyte lysate and shows very weak antimicrobial and cytotoxic properties. The testing of ethyl (E) 4,5-dioxo-2-hexadecenoate (2) and (E)-4-oxo-2-tetradecenoic acid (11) revealed the importance of the free y-oxoacrylic acid unit for the biological activities of 1

Lachnellins A, B, C, D, and naphthalene-1,3,8-triol, biologically active compounds from a Lachnellula species (ascomycetes).

Abstract In the course of our search for new biologically active metabolites, lachnellin A (1), a metabolite with high cytotoxic and antimicrobial activities, the structurally related lachnellins B, C and D (3, 4, 7), and naphthalene-1,3,8-triol (8), an inhibitor of malate synthase (EC 4.1.3.2), were isolated from submerged cultures of the ascomycete Lachnellula sp. A 32 -8 9 . The antimicrobial, cytotoxic and phytotoxic activities of lachnellin A depended on its reactivity and could be abolished by the addition of cysteine. The enzyme inhibiting activity of (8) was due to reactive intermediates during melanization and was no longer observed in the presence of serum albumin. In addition, rac-scytalone (9), (+)-trans-3,4-dihydro-3,4,8-trihy-droxy-1(2H)-naphthalenone (10). 2,5-dihydroxytoluene (11), and (R)-(-)-5-methylmellein (12) were obtained from the same source and biologically characterized.