The highly stereoselective synthesis of the ansa chain segment 23 of streptovaricin U and protostreptovaricins (I and 11) is achieved by stereospecific methylation of y,&epoxy acrylates with trimethylaluminium.
The enal 15 was synthesized in enantiomerically pure form starting from (S)-3-benzyloxy-2-methylpropanol 3 via highly regio-and stereo-selective methylation of the +epoxy acrylate 5 with trimethylaluminium in the presence of water, developing an enantiospecific route to tirandamycin B.
Beta-cyclomannin, a cyclic oligosaccharide consisting of seven alpha-D-mannosides connected together by the (1-->4) glycoside linkage, has been efficiently synthesized by the OsO4 oxidation of heptakis(2,3-didehydroxy)-beta-cyclodextrin which was prepared from beta-cyclodextrin by a five-step transformation. The novel cyclooligosaccharide not only showed water solubility high enough to meet the requirement for drug formulation but also demonstrated strong binding ability toward guest molecules. [reaction: see text]
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