Total Synthesis and Structural Elucidation of the Antifungal Agent Papulacandin D
摘要:
Condensation of the aryllithium reagents, prepared from the bromides 10 and 11 and tert-butyllithium, with lactone 19 and acid-catalyzed spirocyclization gave the papulacandin spiroketals 14 and 15. Subsequent protection using di-tert-butylsilyl bis(trifluoromethanesulfonate) gave the diols 31 and 30. Isoleucine (37) was converted using a double Wittig reaction sequence and propargylation of the intermediate aldehyde 46 into the alkynol 47. Separation of the C-7 epimers of 47 was achieved using kinetic resolution via Sharpless epoxidation. Both alkynol epimers 53 and 57 were converted into the papulacandin side chain esters 65 and 66 using a hydrozirconation and palladium(0)-catalyzed coupling sequence. Comparisons of Mosher ester derivatives of 65 and 66 with the Mosher ester derivative of the natural papulacandin side chain and further degradation were consistent with the stereochemistry of the natural product being 7S,14S. Esterification of the spiroketals with the mixed anhydride 70 and global deprotection gave papulacandin D (1).
A total synthesis of the antifungal agent papulacandin D is reported. The molecule is representative of a large class of C-aryl glycosides that exhibit significant antifungal activity. The synthetic strategy bifurcates the molecule into two nearly equal subunits, the arylglycoside and 18-carbon fatty acid side chain. The key strategic transformations are (1) the palladium catalyzed, organosilanolate-based cross-coupling of a protected glucal silanol and (2) a catalytic enantioselective allylation of a dienal using allyltrichlorosilane. The synthesis was accomplished in 31 steps overall from commercial starting materials to afford over 50 mg of the natural product.
Approaches towards the synthesis of papulacandin D: preparation and structural elucidation of the acyl side chain
作者:Anthony G. M. Barrett、Michael Peña、J. Adam Willardsen
DOI:10.1039/c39950001145
日期:——
Both degradation and total synthesis from L-(+)-isoleucine are used to establish the absolute stereochemistry of the O-3′-acyl side chain of papulacandin D.
作者:Scott E. Denmark、Tetsuya Kobayashi、Christopher S. Regens
DOI:10.1016/j.tet.2010.03.093
日期:2010.6
A total synthesis of (+)-papulacandin D has been achieved in 31 steps, in a 9.2% overall yield from commercially available materials. The synthetic strategy divided the molecule into two nearly equal sized subunits, the spirocyclic C-arylglycopyranoside and the polyunsaturated fatty acid side-chain. The C-arylglycopyranoside was prepared in 11 steps in a 30% overall yield from triacetoxyglucal. The fatty acid side-chain was also prepared in 11 steps in a 30% overall yield from geraniol. The key strategic transformations in the synthesis are: (1) a palladium-catalyzed, organosilanolate-based cross-coupling reaction of a dimethylglucal-silanol with an electron-rich and sterically hindered aromatic iodide and (2) a Lewis-base catalyzed, enantioselective allylation reaction of a dienal and allyltrichlorosilane. A critical element in the successful execution of the synthesis was the development of a suitable protecting group strategy that satisfied a number of stringent criteria. (C) 2010 Elsevier Ltd. All rights reserved.
Total Synthesis of Papulacandin D
作者:Scott E. Denmark、Christopher S. Regens、Tetsuya Kobayashi
DOI:10.1021/ja070071z
日期:2007.3.1
A total synthesis of the antifungal agent papulacandin D is reported. The molecule is representative of a large class of C-aryl glycosides that exhibit significant antifungal activity. The synthetic strategy bifurcates the molecule into two nearly equal subunits, the arylglycoside and 18-carbon fatty acid side chain. The key strategic transformations are (1) the palladium catalyzed, organosilanolate-based cross-coupling of a protected glucal silanol and (2) a catalytic enantioselective allylation of a dienal using allyltrichlorosilane. The synthesis was accomplished in 31 steps overall from commercial starting materials to afford over 50 mg of the natural product.
Total Synthesis and Structural Elucidation of the Antifungal Agent Papulacandin D
作者:Anthony G. M. Barrett、Michael Peña、J. Adam Willardsen
DOI:10.1021/jo951895e
日期:1996.1.1
Condensation of the aryllithium reagents, prepared from the bromides 10 and 11 and tert-butyllithium, with lactone 19 and acid-catalyzed spirocyclization gave the papulacandin spiroketals 14 and 15. Subsequent protection using di-tert-butylsilyl bis(trifluoromethanesulfonate) gave the diols 31 and 30. Isoleucine (37) was converted using a double Wittig reaction sequence and propargylation of the intermediate aldehyde 46 into the alkynol 47. Separation of the C-7 epimers of 47 was achieved using kinetic resolution via Sharpless epoxidation. Both alkynol epimers 53 and 57 were converted into the papulacandin side chain esters 65 and 66 using a hydrozirconation and palladium(0)-catalyzed coupling sequence. Comparisons of Mosher ester derivatives of 65 and 66 with the Mosher ester derivative of the natural papulacandin side chain and further degradation were consistent with the stereochemistry of the natural product being 7S,14S. Esterification of the spiroketals with the mixed anhydride 70 and global deprotection gave papulacandin D (1).