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Synthesis of the Spirastrellolide A, B/C Spiroketal: Enabling Solutions for Problematic Au(I)-Catalyzed Spiroketalizations
- Butler, Barry B., Manda, Jagadeesh Nagendra, Aponick, Aaron
- Organic letters 2015 v.17 no.8 pp. 1902-1905
- ambient temperature, catalysts, chemical reactions, chemical structure, gold, organic compounds, regioselectivity, stereochemistry
- A synthesis of the spirastrellolide A, B/C-ring monounsaturated spiroketal is reported. The key step relies on a Au-catalyzed spiroketalization of a propargyl triol employing an acetonide as a regioselectivity regulator. Through observation and analysis, a set of conditions has been developed that facilitates the use of a mixture of diastereomeric substrates, obviating the need to control the stereochemistry of the propargyl stereocenter and enabling a convenient retrosynthetic disconnection. The key reaction proceeds in 80% yield in 1 min at ambient temperature with the Me₃PAuCl/AgOTf catalyst system. These conditions should be widely applicable for new synthetic endeavors as they appear to overcome all issues with the Au-catalyzed spiroketalization.