Okadaic acid molecular structure

Figure 5.59 Molecular structures of the diarrhetic shellfish poisons (a) pectenotoxin-6 (PTX6) (b) okadaic acid (OA) (c) dinophysistoxin-1 (DTXl) (d) yessotoxin (YTX). Reprinted from J. Chromatogr., A, 943, Matrix effect and correction by standard addition in quantitative liquid chromatographic-mass spectrometric analysis of diarrhetic shellfish poisoning toxins , Ito, S. and Tsukada, K., 39-46, Copyright (2002), with permission from Elsevier Science.

Figure 12.1. Structures of known okadaic acid analogues (Hu et al. 1992, 1995b). MW = molecular weight.

Because of their complex chemical structures and significant biological properties, polyether ionophore antibiotics have stimulated intensive studies of their total synthesis, which primarily require new synthetic methodologies for the control of stereochemistry in acyclic systems two excellent reviews covered the results until 1981 [1]. However, since then, only a few total syntheses have been achieved, because the extremely complex structures of the polyethers have required formidable efforts for synthesis, and much attention has focussed on efficient and stereoselective synthesis of the molecular framework of substituted tetrahydrofurans and tetrahydropyrans and spiroketal systems [2]. This review deals with the total synthesis of three representative complex polyethers, okadaic acid (1), antibiotic X-206 (2), and salinomycin (3) mainly focussing on the latter half of their synthesis. 

Okada et al. have worked extensively on biodegradable polymers based on dianhydroalditols as carbohydrate renewable resources. A series of polyesters were synthesized by the bulk polycondensation of the respective three stereoisomeric dianhydroalditols (DAS, DAM, and DAI) with aliphatic dicarboxyUc acid dichlorides of 2-10 methylene groups [21, 22]. It was found that the biodegradability of the polyesters varied significantly depending on their molecular structures. 

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