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Kinetically controlled one-pot formation of DEFGH-rings of type B physalins through domino-type transformations
Masaki Morita1, Go Hirai, Megumi Ohkubo
1RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
Abstract:
The characteristic DEFGH-ring system of type B physalins has been synthesized by means of a one-pot procedure incorporating domino-type ring transformations. Unexpectedly, we found that introduction of an α-hydroxyester functionality at C17 in ring E allowed the key 7-endo oxy-Michael reaction to proceed. Originally this was thought to be an unfavored process. This afforded the desired caged ring system to be formed in a kinetically controlled manner. Consecutive treatment with AcOH at 100 °C furnished the DEFGH-ring system in one pot.
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