Marine natural products: new results from Red Sea invertebrates

New metabolites isolated from soft corals and sponges of the Red Sea are discussed. It is the aim of this report to describe several marine natural products which have recently been isolated and identified by us. The report will include metabolites of sponges and soft corals collected in the straits of the Gulf of Eilat and the Gulf of Suez, The Red Sea(Ref.1). Diterpenoids from Spongia arabica and Dysidea spp. officinalis var. arabica, Vacelet) we have isolated several diterpenes. The major two compounds were the known 30(,17,19-trihydroxyspongia-13(16),14-dien-2-one(~) and the corresponding 3~,17,19-trihydroxy spongian derivative (2) (Ref.2), and as minor constituents From the sponge Svoneia arabica (SDoneia the new 19-acetoxy, 3W-hydroxyspongia-13(16),14-dien-2-one ( 3 ) and compound structure of & designated spongialactone A, C2 H2605, was mainly elucidated NMR data including 2D NMR experiments. Spongiayactone A is the first A-seco . which ring A closid up to a E-lactone. Rearranged spongians in which all four rings have been changed are well known both from sponges (Ref. 3) and from Dorid nudibranches which feed on sponges (Ref .4). Ten new rearranged spongian-type diterpens have been isolated by us from two Red Sea Dvsideq sponges. All new compounds embody as a .-z 6 carbobicyclic portion either a ~~~~~~~: IhahominB (2-2), or a A system, shahamins F-J(U-B), and carry one out of four heterocycles, that is, a disubstituted dihydro furan, a trisubstituted y-lactol a trisubstituted S-lactone or a 2,7-dioxabicyclo[3.2.l]octane (Fig.1). The latter Fig. 1 moiety is part of macfarlandin E (u)(Ref.3) which was the major diterpene in the examined Dvsidea sponges. The structure of all the compounds were elucidated from spectral data, mainly by 1D and 2D NMR techniques, by comparison with other related known diterpenes (Ref.3 & 4 ) and by mass spectra. ---