Polyacetylenes spiroketals

About seven hundred polyacetylenes have been isolated so far mainly from plants belonging to the family of Asteraceae, Umbelliferae and Campanulaceae [11]. Polyacetylenes occur principally as straight chain polyines, allenes, phenyl, thiophenyl, thioether and spiroketal-enoether derivatives in a quite high yield. Thiophenes and related sulfur compounds are usually grouped together with die polyacetylenes because of their common biosynthetic pathways [11]. Few plant-derived lactones, butenolides and phospholipids show antiviral activity. The antiviral activities of thiophenes, polyacetylenes, lactones, butenolides and phospholipids from plant origin are reported in table 8. 

The postulated role of polyacetylenes as precursors of spiroketals has received support from in vitro syntheses reported by Bohlmann and Florentz (1966) and from the isolation from Chrysanthemum serotinum L. of the following two triynes ... 

These can formally act as precursors for all of the polyacetylenes of Chrysanthemum serotinum, which contains a number of spiroketals (Bohlmann and Kapteyn, 1966). 

The biogenesis of spiroketals from polyacetylenes has been demonstrated using tagged precursors (Bohlmann, 1966). 

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