Stereocontrolled Elaboration of Natural (-)-Polycavernoside A, a Powerfully Toxic Metabolite of the Red Alga Polycavernosa tsudai
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- 作者：Leo A. Paquette ; Louis Barriault ; Dmitri Pissarnitski ; and Jeffrey N. Johnston
- 刊名：Journal of the American Chemical Society
- 出版年：2000
- 出版时间：February 2, 2000
- 年：2000
- 卷：122
- 期：4
- 页码：619 - 631
- 全文大小：524K
- 年卷期：v.122,no.4(February 2, 2000)
- ISSN：1520-5126
文摘
A stereoselective total synthesis of natural levorotatory polycavernoside A (1) has been achieved.Initial investigations produced the properly activated disaccharide unit 18b via the conjoining of buildingblocks originating from L-fucose and D-xylose. This objective was followed by preparation of the phenylsulfonyl-substituted tetrahydropyran 23 and aldehyde 30. After proper linking of these key compounds, importantinformation had to be garnered on the sequence of steps that would ultimately result in successful access to1. Although oxidation to generate 
-diketone 35 and unmasking of the C-13 hydroxyl did give rise efficientlyto lactol 36, this functionality did not pave the way for ensuring macrolactonization. When this sequence ofsteps was reversed, it was indeed possible to arrive at the heavily functionalized precursor 44. However,numerous experiments failed to result in the requisite activation of C-16 for attachment of the trienyl sidechain. However, if the E-vinyl iodide was elaborated in advance of -diketone generation, glycosidation, andcomplete side chain construction, arrival at 1 proceeded without unsurmountable complications to furnish thetargeted marine toxin.
-diketone 35 and unmasking of the C-13 hydroxyl did give rise efficientlyto lactol 36, this functionality did not pave the way for ensuring macrolactonization. When this sequence ofsteps was reversed, it was indeed possible to arrive at the heavily functionalized precursor 44. However,numerous experiments failed to result in the requisite activation of C-16 for attachment of the trienyl sidechain. However, if the E-vinyl iodide was elaborated in advance of -diketone generation, glycosidation, andcomplete side chain construction, arrival at 1 proceeded without unsurmountable complications to furnish thetargeted marine toxin.