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Updated: Jun 16, 2026

Efficient Construction of Drug-like Bispirocyclic Scaffolds Via Organocatalytic Cycloadditions of α-Imino γ-Lactones and Alkylidene Pyrazolones
Published on: February 7, 2019
ASYMMETRIC SYNTHESIS OF THE ABCD RING SYSTEM OF DAPHNILACTONE B VIA A TANDEM, DOUBLE INTRAMOLECULAR, [4+2]/[3+2]
Scott E Denmark1, Son T Nguyen, Ramil Y Baiazitov
1Department of Chemistry, Roger Adams Laboratory, University of Illinois, Urbana, Illinois 61801, denmark@scs.uiuc.edu.
Abstract:
An asymmetric synthesis of the ABCD ring system of daphnilactone B is described. The synthesis features a tandem, double intramolecular, [4+2]/[3+2] cycloaddition of a highly functionalized, enantiomerically enriched nitroalkene to generate a pentacyclic nitroso acetal. The cycloaddition establishes six contiguous stereogenic centers including the critical CD ring junction that bears two quaternary stereogenic centers. Hydrogenolysis of the nitroso acetal followed by amide reduction and cyclization provided the AB rings. The methyl substituent on the A ring was installed in the correct configuration via hydrogenation of an exocyclic olefin in the final step.
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