Enantioselective total synthesis of heliespirone B
摘要:
The first enantiocontrolled total synthesis of heliespirone B has been accomplished employing a biomimetic intramolecular oxy-Michael reaction followed by the regio- and diastereoselective reduction of the carbonyl function as key steps. (C) 2012 Elsevier Ltd. All rights reserved.
The enantioselective syntheses of the compounds with the assigned structures of the helibisabonols A and B have been accomplished. Using an enzymatic desymmetrization of the sigma-symmetrical diol (route a) and a diastereoselective conjugate addition of the methyl to the enone with a chiral auxiliary (route b) we constructed the key tertiary stereogenic center at the benzylic position (C7) and then used an asymmetric dihydroxylation for assembling the C10 stereogenic center. In addition, possible diastereoisomers of the natural products were prepared and detailed comparisons of the H-1 and C-13 NMR spectra were conducted. As a result, the structure originally assigned to helibisabonol A may be revised to (7R,10R)-1. In the case of helibisabonol B, the (7R,10R)-2 would be reasonable based on a comparison of the NMR data and the biogenetic parallelism with helibisabonol A. (C) 2011 Elsevier Ltd. All rights reserved.
An efficient totalsynthesis of (+)-heliannuol D was accomplished in 14 steps and in 12% overall yield by employing a diastereoselective conjugate addition reaction to create a tertiary benzylic stereogenic center and simple assembly of the functionalized oxepane framework by an efficient one-pot transformation procedure as the key steps.
The first enantiocontrolled total synthesis of heliespirone B has been accomplished employing a biomimetic intramolecular oxy-Michael reaction followed by the regio- and diastereoselective reduction of the carbonyl function as key steps. (C) 2012 Elsevier Ltd. All rights reserved.