EXTENSIVE 1D-NMR AND 2D-NMR AND X-RAY STUDIES OF DITERPENES ISOLATED FROM THE MARINE ALGA DICTYOTA-PARDALIS F PSEUDOHAMATA

From the lipophilic extract of the marine alga Dictyota pardalis f. pseudohamata, four new diterpenes [1-4] of the dolastane and dolabellane classes have been isolated and characterized by spectroscopic (nmr, ir, ms, and X-ray) methods. Together with the new natural produces, the previously reported compounds 5-8 were also isolated. Single-crystal X-ray analysis of compounds 1, 9, and 11 has permitted their absolute configurations to be assigned. For compounds 5 and 6, complete stereochemical assignments are reported. Unambiguous H-1- and C-13-nmr assignments are made for compounds 1-8. The results of the current investigations are compared with the results of a former study of the same algal species.