Amiram Groweiss

Latrunculin, a new 2-thiazolidinone macrolide from the marine sponge latrunculia magnifica

Abstract Three new toxins were isolated from the Red Sea sponge Latrunculia magnifica A full structure determination of these toxins, by spectroscopic methods, was aided by an X-ray diffraction analysis of a crystalline derivative ( 1 b) of latrunculin-A. The Latrunculins exhibit a new class of 14 and 16 membered macrolides to which the rare 2-thiazolidinone moiety is attached. A biogenesis of these biologically active compounds is put forward.

Latrunculins: NMR study, two new toxins and a synthetic approach

Abstract A complete 1H and 13C NMR assignment of one of the latrunculins (B) was accomplished with the aid of 2D NMR COSY and CH shift-correlation experiments. The various H-H Coupling constants have been datermined and a conformation of the macrolide and the tetrahydropyran (THP) ring suggested on basis of the J-values and measured NOEs. The absolute configuration of latrunculin-A( 1 ) was determined on the grounds of its earlier X-Ray analysis, and a chemical degradation to a known compound. Two novel latrunculins, -C( 3 ) and -D( 4 ), were isolated from the Red Sea sponge L. magnifica and their structures elucidated. Starting with L-cysteine a synthon for the latrunculins has been synthesized.

Sipholenol and sipholenone, two new triterpenes from the marine sponge (levi).

Abstract Several squalene-derived triterpenes possessing a hitherto unknown ring system were isolated from the Red Sea Sponge, Siphonochalina siphonella . The structure of one of the new compounds, sipholenol ( 1 a), was determined by spectroscopic methods including a full x-ray diffraction analysis.

Recent research in marine natural products from the Red Sea

New metabolites isolated from soft corals and sponges collected in the Gulf of EiIat (The Red Sea) since 1974 are discussed.

Several new cembranoid diterpenes from three soft corals of the red sea

Abstract Eight new diterpenoids have been isolated from three soft corals, Alcyonium utinomii, Lobophytum pauciflorum and Lobophytum crassum. The compounds were shown to be: 1,3,7,10-cembratetraen-12-ol(4); 1,3,6,11-cembratetraen-8-ol5; 1,3,7,12(20)-cembratetraen-ll-ol (6a); 2,7,11-cembratrien-4,15-diol(8); 3,7,10-cembratrien-12, 15-diol(9); and the lobolide related deacetyldeepoxy lobolide (15), deepoxy lobolide (16) and deacetyl-13-hydroxy lobolide (17), by spectral data and chemical studies (mainly ozonolysis).

Attempted acid-catalyzed transannular reactions in the cembranoids

Abstract Several cembrane diterpenes were treated by various acids under different experimental conditions. All tested compounds were found to be acid sensitive, leading either to local chemical transformations (e.g. opening of epoxides), to transannular reactions and/or to unidentified mixtures. Sarcophine ( 7 ), the principal cembrane tested, was found to afford either all types of possible epoxide opening products ( 11–22 ), or, by a transannular reaction, when treated with SnCl 4 , two tetrahydrooxepine derivatives (23 and 24). The structure determination of the various derivatives of sarcophine was based mainly on the 1 H and 13 C-NMR spectra and also on several chemical transformations. Flaccidoxide ( 8 ), another cembranoid examined, was found to yield, with Zn/Cu couple, the expected deoxygenation product (sarcophytol-B, 32 ) together with an unexpected transannular reaction product ( 33 ). The structure, including the stereochemistry, of the latter THF-derivative of 8 ( 33 ) was elucidated by NMR and chemical reactions.