7500-58-5Relevant articles and documents
Complete relative stereochemistry of maitotoxin
Zheng,DeMattei,Wu,Duan,Cook,Oinuma,Kishi
, p. 7946 - 7968 (2007/10/03)
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.
Enzymes in Organic Synthesis. 41. Stereoselective Horse Liver Alcohol Dehydrogenase Catalyzed Reductions of Heterocyclic Bicyclic Ketones
Lam, Lister K. P.,Gair, Iain A.,Jones, J. Bryan
, p. 1611 - 1615 (2007/10/02)
Preparative-scale horse liver alcohol dehydrogenase catalyzed reductions of racemic cis and trans bicyclic O- and S-heterocyclic ketones proceed with high enantiomeric selectivity.The diastereotopic selectivity for the pro-R faces of the carbonyl groups is also very high.The ee's of all but one of the product alcohols are >97percent.The ee's of the recovered ketones are in the 52-60percent range.The results confirm that an ether-oxygen or -sulfur substituent does not alter the enzyme's overall structural specificity or stereospecificity toward its ketone substrates.
