A Stereoelectronic Model To Explain the Highly Stereoselective Reactions of Nucleophiles with Five-Membered-Ring Oxocarbenium Ions

Chemical Synthesis of Furanose Glycosides

“…As mentioned above, this is likely due to the conformational flexibility of the furanose ring, which leads to a number of potential intermediates/reaction trajectories with similar transition state energies. Elegant  work by Woerpel and coworkers has led to the development of the "inside-attack" model for the synthesis of furanose C-glycosides (71). This work has influenced thinking on the synthesis of furanose O-glycosides, but a fundamental challenge that remains is to develop methodologies that lead to a single intermediate that can react through this manifold.…”

“…17). Based on the "inside attack rule" developed by Woerpel and coworkers (71), these donors were developed with the expectation that the favored conformation of the oxacarbenium ion intermediate was one (e.g., 75) in which the alcohol would add stereoselectively to give the 1,2-cis-glycoside. Density functional-theory calculations support this hypothesis (68), as does the crystal structure of a thioglycoside similar to 69 (98).…”

Total Syntheses of Amphidinolides T1 and T4 via Catalytic Stereoselective, Reductive Macrocyclizations.

“…11 Woerpel and coworkers have also conducted extensive studies regarding the stereochemical course of similar transformations (Scheme 5) in which 2-acetoxy-4,5-cis-disubstituted tetrahydrofuran derivatives undergo allylation with a high degree of stereocontrol to deliver products possessing a 2,4,5-trans-cis relationship across the tetrahydrofuran ring. 12 Encouraged by this stereochemical precedent, we needed to choose an appropriate propargyl nucleophile equivalent 13 to effect the desired addition reaction. At the onset of our investigations, we focused on Danheiser's reports 14 of allenylsilanes as effective propargyl nucleophiles in related Lewis acid-mediated additions to acyclic acetals, aldehydes and ketones.…”

The Effect of Sulfoxides on the Stereoselective Construction of Tetrahydrofurans: Total Synthesis of (+)‐Goniothalesdiol

“…Other similar reactions that give rise to cyclic ethers, such as the Mead reductive cyclization of ketones that have a b-lactone three carbon atoms distant from the alcohol, [25,26] and the nucleophilic substitution of g-lactols and cyclic acetals, [27][28][29] also proceed via these intermediates. [30][31][32] The study of oxocarbenium ion reactivity is of huge interest because these ions occur as intermediates in many interesting synthetic and bioorganic reactions, including the formation and cleavage of glycosides.…”