No abstract

Synthetic analysis of spirastrellolide E envisioned to entail a cross-metathesis union of the northern and southern hemispheres followed by a Sharpless epoxidation/methylation sequence to achieve the C(22,23) stereogenicity leads to the design of a C(1)–C(23) advanced southern hemisphere exploiting a gold-catalyzed directed spiroketalization as a key step. Stereochemical analysis of this strategic transformation provides insight on the impact of the directing group carbinol stereogenicity on the reaction efficiency and, in turn, permits the conversion of the minor isomer of the spiroketal precursor to the requisite congener for successful spiroketalization.

The 4,5-dihydropyrazole motif has drawn considerable attention over the years as it was shown to exhibit a plethora of biological and pharmacological properties, including anticancer, antibacterial, antifungal, antiviral, and anti-inflammatory properties. As such, it has been the target of a number of methods and drug discovery programs. We report here a straightforward and highly selective approach featuring a key palladium-catalysed Tsuji-Trost type C-allylation and subsequent intramolecular 1,4-addition of hydrazones.

A highly enantioselective synthesis of -branched acrylonitriles is reported featuring an unprecedented formal cross Rauhut-Currier reaction consisting of an asymmetric Michael addition/retro-Dieckmann/retro-Michael fragmentation cascade. The method, which involves the use of an acrylonitrile surrogate, is practical, scalable and highly versatile, and provides a straightforward access to a wide range of enantioenriched nitrile-containing building blocks without using acrylonitrile or any source of cyanide. Most importantly, it offers a new tool to incorporate an acrylonitrile moiety in an asymmetric fashion.