Total Synthesis of Brevetoxin A: Part 1: First Generation Strategy and Construction of BCD Ring System
摘要:
Discussed herein is our first generation strategy for the total synthesis of brevetoxin A. This approach relies upon dissection of the molecule at the nine-membered ring site (ring E), A Wittig coupling of requisite polycyclic fragments 3 and 4 followed by hydroxy dithioketal cyclization was expected to furnish the polycyclic framework of brevetoxin A (1). Intermediate 8 was anticipated to be a valid synthetic precursor to phosphonium salt 3, and its synthesis was accomplished by a bis(lactonization)/thionolactone formation/functionalization sequence. In order to test our synthetic strategy, the synthesis of an advanced model system (36) was attempted. Aldehyde 38 and phosphonium salt 37 were successfully synthesized and coupled through a:Wittig reaction. Unfortunately, the planned hydroxy dithioketal cyclization to form the crucial nonacene (ring E) did not proceed as anticipated and this synthetic approach was discontinued.
Total Synthesis of Brevetoxin A: Part 1: First Generation Strategy and Construction of BCD Ring System
摘要:
Discussed herein is our first generation strategy for the total synthesis of brevetoxin A. This approach relies upon dissection of the molecule at the nine-membered ring site (ring E), A Wittig coupling of requisite polycyclic fragments 3 and 4 followed by hydroxy dithioketal cyclization was expected to furnish the polycyclic framework of brevetoxin A (1). Intermediate 8 was anticipated to be a valid synthetic precursor to phosphonium salt 3, and its synthesis was accomplished by a bis(lactonization)/thionolactone formation/functionalization sequence. In order to test our synthetic strategy, the synthesis of an advanced model system (36) was attempted. Aldehyde 38 and phosphonium salt 37 were successfully synthesized and coupled through a:Wittig reaction. Unfortunately, the planned hydroxy dithioketal cyclization to form the crucial nonacene (ring E) did not proceed as anticipated and this synthetic approach was discontinued.
Total Synthesis of Brevetoxin A: Part 3: Construction of GHIJ and BCDE Ring Systems
作者:K. C. Nicolaou、Guo-qiang Shi、Janet L. Gunzner、Peter Gärtner、Paul A. Wallace、Michael A. Ouellette、Shuhao Shi、Mark E. Bunnage、Konstantinos A. Agrios、Chris A. Veale、Chan-Kou Hwang、John Hutchinson、C. V. C. Prasad、William W. Ogilvie、Zhen Yang
Successful syntheses of highly complex intermediates 2 (GHIJ ring system) and 3 (BCDE ring system) for the total synthesis of brevetoxin A (1) are described. Several of our methodologies were utilized to achieve this goal: i) hydroxy epoxide cyclizations of intermediates 22 and 30 (rings I and H, respectively); ii) hydroxy dithioketal cyclization of 45 (ring G); and, iii) palladium-catalyzed coupling with bis(cyclic ketene acetal phosphate) 68 (rings B and D). With the knowledge gained from our previous model studies, 2 and 3 were expected to be pivotal intermediates on the synthetic route to brevetoxin A.
New synthetic strategies for the construction of medium size cyclic ethers. Stereocontrolled synthesis of the BCD ring framework of brevetoxin A
作者:K. C. Nicolaou、D. G. McGarry、P. K. Sommers
DOI:10.1021/ja00165a085
日期:1990.4
NICOLAOU, K. C.;MCGARRY, D. G.;SOMMERS, P. K., J. AMER. CHEM. SOC., 112,(1990) N, C. 3696-3697