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SmI 2 ‐induced cyclizations and their applications in natural product synthesis
Author(s) -
Nakata Tadashi
Publication year - 2010
Publication title -
the chemical record
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.61
H-Index - 78
eISSN - 1528-0691
pISSN - 1527-8999
DOI - 10.1002/tcr.200900027
Subject(s) - sulfone , tetrahydropyran , chemistry , aldehyde , sulfoxide , marine toxin , stereochemistry , total synthesis , natural product , dimethyl sulfoxide , ring (chemistry) , organic chemistry , catalysis , toxin , biochemistry
Abstract Since the isolation of brevetoxin‐B, a red tide toxin, many bioactive marine natural products featuring synthetically challenging trans ‐fused polycyclic ether ring systems have been reported. We have developed SmI 2 ‐induced cyclization of β‐alkoxyacrylate with aldehyde, affording 2,6‐ syn ‐2,3‐ trans ‐tetrahydropyran (THP) or 2,7‐ syn ‐2,3‐ trans ‐oxepane with complete stereoselection, as a key reaction of efficient iterative and bi‐directional strategies for the construction of these polycyclic ethers. This reaction is also applicable to the synthesis of 3‐, 5‐, and 6‐methyl‐THPs and 3,5‐dimethyl‐THP. The synthesis of 2‐methyl‐ and 2,6‐dimethyl‐THPs was accomplished by means of a unique methyl insertion. Recently, the SmI 2 ‐induced cyclization was extended to similar reactions using β‐alkoxyvinyl sulfone and sulfoxide. Reaction of ( E )‐ and ( Z )‐β‐alkoxyvinyl sulfone‐aldehyde afforded 2,6‐ syn ‐2,3 ‐trans ‐ and 2,6‐ syn ‐2,3‐ cis ‐ THPs, respectively. Reaction of ( E )‐β‐alkoxyvinyl ( R )‐ and ( S )‐sulfoxides gave 2,6‐ anti ‐2,3‐ cis ‐ and 2,6‐ syn ‐2,3‐ trans ‐THPs, respectively. Reaction of ( Z )‐β‐alkoxyvinyl ( R )‐sulfoxides gave 2,6‐ syn ‐2,3 ‐cis ‐THP and an olefinic product, while that of ( Z )‐β‐alkoxyvinyl ( S )‐sulfoxide afforded a mixture of many products. These SmI 2 ‐induced cyclizations have been applied to the total syntheses of various natural products, including brevetoxin‐B, mucocin, pyranicin, and pyragonicin. Synthetic studies on gambierol and maitotoxin are also introduced. © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 10: 159–172; 2010: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.200900027