Version:1.0StartHTML:0000000217EndHTML:0000004466StartFragment:0000002645EndFragment:0000004430SourceURL:file://localhost/Users/charleszercher/Presentations/Pacifichem%20Folder/hawaii%20talk%20abstract.doc@font-face {  font-family: 'Times New Roman';}@font-face {  font-family: 'Arial';}p.MsoNormal, li.MsoNormal, div.MsoNormal { margin: 0in 0in 0.0001pt; font-size: 12pt; font-family: 'Times New Roman'; }table.MsoNormalTable { font-size: 10pt; font-family: 'Times New Roman'; }div.Section1 { page: Section1; }The isolation of spiroketal papyracillicacid C from Microsphaeropsis sp., along with the previously identified papyracillic acids Aand B, was reported in 2007. The cytotoxicity of papyracillic acid A isproposed to be due to its reactivity with nucleophiles, with the addition ofthe cysteine to the exocyclic alkene supporting the assertion that thespiroacetal of papyracillic acid A exists in equilibrium with open chain forms.Inspection of the open chain form of a hemiacetalreveals a 1,4-dicarbonyl relationship that could arise from a chain extensionreaction. Application of a tandem zinc carbenoid-mediated chainextension-acylation reaction provides an attractive synthetic route to thesenatural products. This method, in conjunction with a variation on the chainextension methodology that facilitates �-alkyl incorporation, offers a direct route to the racemicskeleton.  In a parallel study, wehave developed a strategy for the control of absolute stereochemistry at the �-carbon.

Synthetic approaches to papyracillic acids A, B, and C

243rd National Meeting (2012)

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