HELIOPORINS - BIOACTIVE DITERPENES FROM THE BLUE CORAL HELIOPORA-COERULEA

Seven new diterpenes, helioporins A-G (1-7), have been isolated from the blue coral Heliopora coerulea. The structures determined by spectroscopic data and chemical conversions are related to the aglycons of pseudopterosins and seco-pseudopterosins, which are antiinflammatory glycosides from Caribbean gorgonians. Treatment of helioporin A (1) with TMSI/NaI followed by Na2S2O3 gave helioporin E (5) and an unusual product (11) resulting from C-C bond cleavage. Reaction of helioporin B (2) with Tf2O/C5H2NMet-Bu2 followed by catalytic reduction gave a cyclization product (14) which was identical with a compound derived from 5. AH helioporins were chemically correlated and their relative stereochemistry was related to that of the aglycon of pseudopterosin G (10). Helioporins A and B showed antiviral activity against HSV1 and C-G cytotoxicity against P388.