Total Synthesis Highlights
Total Synthesis Highlights
Total Synthesis Highlights
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3:1 mixture. That 1 was the major diastereomer followed from its conversion to 3. The<br />
configuration of the minor diastereromer was not noted. Exposure of 1 to nucleophilic azide then<br />
gave the easily-purified 2.<br />
The spirodiepoxide 1 is an intriguing new approach to relative and absolute stereocontrol. It will<br />
be interesting to see what other nucleophiles can be used in the opening. It is possible that a chiral<br />
oxygen transfer reagent, such as the dioxirane prepared by the Shi protocol, would convert 12 to 1<br />
with improved diastereoselectivity (double diastereoselection)<br />
68. Enantioselective <strong>Synthesis</strong> of the Polyene Antiobiotic Aglycone Rimocidinolide Methyl<br />
Ester<br />
The complex polyene macrolide antibiotics are clinically effective as antifungal agents. Scott<br />
Rychnovsky of the University of California at Irvine has reported (Angew. Chem. Int. Ed. 2004, 43,<br />
2822. ) the first synthesis of rimocidinolide methyl ester (4), the aglycone of rimocidin (1). The<br />
key step in the synthesis is the condensation of the aldehyde 2 with the phosphonate 3, leading to<br />
4.<br />
Preparation of the Aldehyde 2: The absolute configuration of the triene aldehyde 2 was set by<br />
Noyori hydrogenation of ethyl butyrylacetate 5. Silylation and Dibal reduction then gave the<br />
aldehyde 6. Reduction of the homologated ester gave the alcohol, which was oxidized to the