By addressing the relative stereochemistry of the four acyclic portions via organic synthesis, the complete relative stereochemistry of maitotoxin (MTX) has been established as 1B. The relative stereochemistry of the C.1−C.15 portion was elucidated via a two-phase approach:  (1) the synthesis of the eight diastereomers possible for model C, representing the C.1−C.11 portion, and the eight diastereomers possible for model D, representing the C.11−C.15 portion, and the comparison of their proton and carbon NMR characteristics with those of MTX, concluding that 9 and 35 represent the relative stereochemistry of the corresponding portions of MTX; (2) the synthesis of the two remote diastereomers 51 and 52, and comparison of their proton and carbon NMR characteristics with those of MTX, concluding that 51 represents the relative stereochemistry of the C.1−C.15 portion of MTX. The relative stereochemistry of the C.35−C.39, C.63−C.68, and C.134−C.142 acyclic portions was established via (1) the synthesis of the 8, 8, and 16 diastereomers possible for models E, F, and G, respectively, and (2) the comparison of their proton and carbon NMR characteristics with those of MTX, concluding that 81, 117, and 187, respectively, represent the relative stereochemistry of the corresponding portions of MTX. Some biogenetic considerations have been given to speculate on the absolute configuration of MTX. The vicinal proton coupling constants observed for models 51, 81, 117, and 187 were used to elucidate their preferred solution conformation. Assembling the preferred solution conformations found for the four acyclic portions allows one to suggest that the approximate global conformation of MTX is represented by the shape of a hook, with the C.35−C.39 portion being its curvature. MTX appears to be conformationally relatively rigid, except for conformational flexibility around the C.7−C.9 and C.12−C.14 portions. On the basis of the experimental results gained in the current work, coupled with those in the AAL-toxin/fumonisin area, it has been pointed out that the structural properties of 51, 81, 117, 187 and their diastereomers are inherent to the specific stereochemical arrangement of the small substituents on the carbon backbone and are independent from the rest of the molecule. Thus, it has been suggested that each of these diastereomers has the capacity to install a unique structural characteristic through a specific stereochemical arrangement of substituents on the carbon backbone, and that fatty acids and related classes of compounds may be able to carry specific information and serve as functional materials in addition to structural materials.

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The unambiguous stereochemical assignment of the V/W-ring juncture of maitotoxin, as shown in Figure , was accomplished using a two-step approach:  (1) the synthesis of two diastereomeric models Me-A and Me-B and (2) the comparison of the NMR spectroscopic data for each model with those of maitotoxin. Furthermore, the fact that the NMR characteristics observed for Me-A were remarkably close to those reported for maitotoxin makes a strong case for the accurate extrapolation of the conformational properties of maitotoxin from those of the model Me-A. Using 1H−1H NOESY experiments and MM3 calculations, the solution conformations of Me- A and Me-B were studied in aprotic and protic solvents. In aprotic solvents such as benzene, both Me-A and Me-B preferentially adopt the conformations Me-Aa and Me-Ba, respectively, due to intramolecular hydrogen bond stabilization. On the other hand, in a protic solvent such as a 1:1 mixture of methanol and pyridine both Me-A and Me-B exist as mixtures of all of their possible rotamers.

A novel series of 4-[N-methyl-N-[(E)-3-[4-(methylsulfonyl)phenyl]-2- propenoyl]amino]benzenesulfonamides has been prepared and evaluated as membrane-bound phospholipase A2 inhibitors. A structure-activity relationship study indicated that the optimum potency was realized with the N-(phenylalkyl)piperidine derivatives 3 and 4. These compounds inhibited the liberation of arachidonic acid from the rabbit heart membrane fraction with IC30 values of 0.028 and 0.009 microM, respectively. Several compounds (3, 4, and 28), which proved to be potent inhibitors in vitro, significantly reduced the size of myocardial infarction in coronary occluded rats by iv administrations prior to the ligation. N-(1-Benzyl-4-piperidinyl)-4-[N-methyl-N-[(E)-3-[ 4-(methylsulfonyl)phenyl]-2-propenoyl]amino]-benzenesulfonamide (3, ER-3826), which showed the protective in vivo effects at doses higher than 0.3 mg/kg iv, was finally chosen as a leading candidate.