A Zn(OTf)-promoted cyclization reaction of tosylhydrazones with 2-(dimethylamino)malononitrile has been successfully developed providing an efficient strategy for the synthesis of substituted 1-tosyl-1H-pyrazoles.
The catalytic asymmetric total syntheses of the biologically important and therapeutically valuable Amaryllidaceae alkaloids (−)-galanthamine and (−)-lycoramine have been divergently achieved from commercially available 3-butyn-1-ol. A newly developed spirocyclic pyrrolidine (SPD)-catalyzed enantioselective Robinson annulation rapidly constructs the key cishydrodibenzofuran core, which bears an all-carbon quaternary stereocenter of the target molecules with an excellent stereoselective control. Additionally, the current asymmetric synthetic strategy provides an alternative approach toward the syntheses of (−)-galanthamine and its analogues.
(‒)-Morphine, which is selected as an essential medicine by World Health Organization, is widely applied in the treatment of the pain-related diseases. Due to its synthetically challenging molecular architecture and important clinical role, extensive synthetic studies of morphine-type alkaloids have been conducted. However, catalytic asymmetric total synthesis of (‒)-morphine remains a long-standing challenge. Here, we disclose an efficient enantioselective total synthesis of (‒)-morphine in a longest linear sequence of 16 steps. The key transformation features a highly enantioselective Robinson annulation enabled by our spiro-pyrrolidine catalyst to rapidly construct the densely functionalized
cis
-hydrodibenzofuran framework containing vicinal stereocenters with an all-carbon quaternary center. This asymmetric approach provides an alternative strategy for the synthesis of (‒)-morphine and its analogues.
We report an asymmetric construction of multi-substituted 3H-spiro[benzofuran-2,1’-cyclopentane]s with three new stereocenters and two new ring systems.
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