Amphidinolide absolute stereochemistry

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. ° ... 

Amphidinolide C (3a) is a 25-membered macrolide isolated from Amphidinium sp. (strain Y-5), possessing an s-cis and an s-trans Aienes, two fxo-methylenes, two tetrahydrofuran rings, a 1,2-diol, and four branched methyl groups. The relative stereochemistry of the C-l-C-8 and C-20-C-23 portions has been elucidated by NOESY correlations of amphidinolide C (3a) and its 7,8-0-isopropylidene derivative. Application ofthey-based configuration analysis revealed the etythro-m xion for the C-12-C-13 bond and the relation for the C-23—C-24 bond. The absolute... 

Amphidinolide Q (16), C21H34O4, is a 12-membered macrolide possessing four branched methyl groups, an a ti-methylene, and a ketone carbonyl, isolated from the marine dinoflagellate Amphidinium sp. (strain Y-5). The relative stereochemistry of amphidinolide Q (l) was elucidated on the basis of -based configuration analysis method and NOESY correlations. The absolute configurations of amphidinolide (16) were concluded to he AR, 7R, 9S, 115, and 135 by application of the modified Mosher s method to amphidinolide 0 (16) and the linear methyl ester derivatives of amphidinolide... 

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