Synthesis of nor-sesquiterpene spirolactones and their steroidal hybrids revisited. The neopentyl dilemma: misassignment of one stereocentre may necessitate a completely new approach
摘要:
Inversion at the highly congested Cl position of 1-epi-pathylactone A (1-epi-1), or its corresponding steroidal hybrid 8a, using a diverse range of published procedures including microwave assisted Mitsunobu reaction or via oxidation to the corresponding ketone and subsequent reduction, was unsuccessful in our hands. Attempts to convert the Cl hydroxyl group into its corresponding chloride, en route to napalilactone 2a, also failed. Precursors with the Cl cc configuration installed at early stage proved not to be amenable to the targets under a broad range of conditions. (C) 2014 Elsevier Ltd. All rights reserved.
Enantioselective Total Synthesis of 1-epi-Pathylactone A
摘要:
The first enantioselective total synthesis of 1-epi-pathylactone A, 3, has been accomplished using a PhI(OAc)(2)-mediated domino reaction as a key step. No diastereomeric separation was required throughout the whole synthetic scheme presented in this paper. Comparison of H-1 and C-13 NMR spectral data of the synthetic product with the reported spectral data of natural pathylactone A, coupled with an X-ray crystallographic analysis, led to the conclusion that the C1 configuration in the original paper was erroneously ascribed to (R).