The principal acetylenic metabolites of the basidiomycete B. 841 (probably a Poria sp.) are known to be the hydroxy acids nemotinic acid (I) and odyssic acid (II), together with derivatives such as the corresponding lactones (Bu'Lock, Jones & Leeming, 1955, 1957). Acetylenic compounds of various kinds are now known to be relatively common constituents of certain groups of plants and fungi, and ...

Betulin derivatives are a widely studied group of compounds of natural origin due to their wide spectrum of biological activities. This paper describes new betulin derivatives, containing a phosphonate group. The allyl-vinyl isomerization and synthesis of acetylenic derivatives have been reported. Structural identification of products as E and Z isomers has been carried out using ¹H-, (13)C-, (...