Amphidinolide structure elucidation

The toxicity of HMPA can be avoided by using N.N -dimethylpropylene urea (DMPU)543 or DMF as the solvent.511 The beneficial hardiness of SEM groups was the cause of problems attending deprotection of the intermediate 297.1 [Scheme 4.297] during studies aimed at the structural elucidation of the macro-tide Amphidinolide L.544 Treatment of 297.1 with TBAF in HMPA returned the desired did 297<2 (35%) along with triethylsilyl-deprotected compound 2973 (33%) and the ethoxymethyl ether 297,4 (11%). However, when DMPU was used as solvent, the desired dial 297-2 was obtained in 82% yield. 

Two reviews have been devoted to structure elucidation, mostly by the use of NMR methods, of the compounds isolated from marine organisms. One has been written by Ciminiello and Fattorusso on shellfish toxins from northern Adriatic mussels, the other, by Kobayashi and Tsuda, covers a series of cytotoxic macrolides named amphidinolides, isolated from symbiotic marine dinoflagellates of the genus Amphidinium which were separated from inside cells... 

Amphidinolides B6 (2f) and B7 (2g) have been isolated from a marine dinoflagellate Amphidinium sp. (strain HYA002), which was isolated from the marine acoel flatworm Amphiscolops sp. collected off Sunabe beach, Okinawa. The planer structures of amphidinolides B6 (2f) and B7 (2g) were elucidated from the detailed analyses of 2D NMR spectra. Relative stereochemistries of these macrolides were deduced from NOESY data... 

The absolute configurations at C-7, C-8, and C-10 were elucidated to be S, S, and 5, respectively, by comparison of the NMR data of C-l-C-12 segments with those of synthetic model compounds for the tetrahydrofuran portion. The structure of amphidinolide T1 (19a) has been confirmed by a single crystal X-ray analysis.Amphidinolide T1 (19a) possesses an odd-numbered macrocyclic lactone ring but has no vicinally located one-carhon branches. 

Amphidinolide W (22), a 12-membered macrolide possessing four branched methyl groups and no exo-methylene, was isolated from the marine dinoflagellate Amphidinium sp. (strain Y-42)d° The gross structure was elucidated on the basis of the spectroscopic data including NMR correlations obtained from an... 

Amphidinolide Y (24) is a 17-membered macrolide obtained together with amphidinolide X (23), and it was elucidated to exist as a 9 1 equilibrium mixture of 6-keto and 6(9)-hemiacetal forms on the basis of 2D NMR data. The structure and absolute stereochemistry of the 6-keto form were assigned on the basis of spectroscopic data and chemical conversion of amphidinolide Y (24) into amphidinolide X (23) by Pb(OAc)4 oxidation. The 6-keto form of amphidinolide Y (24) is a 17-membered macrolide possessing a tetrahydrofuran ring, five branched methyl groups, a ketone, and two hydroxy groups. ° ... 

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