Fe²⁺ Catalyzes Vitamin E-Induced Fragmentation of Hydroperoxy and Hydroxy Endoperoxides That Generates γ-Hydroxy Alkenals

The formation of cytotoxic γ-hydroxyalkenals has been generally viewed as the consequence of free radical-induced oxidation of polyunsaturated fatty acyls through the decomposition of lipid peroxides. Vitamin E (Vit E) would be expected to inhibit such autoxidation. In a model study, we now find that fragmentation of a hydroperoxy endoperoxide generated the lactone of a γ-hydroxyalkenal. With 1 equiv of Fe2+, or with a catalytic amount (0.1 equiv) of Fe2+ and 1 equiv of Vit E, the yields are 43−50%. However, Vit E alone did not promote the fragmentation, and a catalytic amount of Fe2+ alone only afforded a low yield (about 5%). Vit E could contribute to, as opposed to preventing, the formation of γ-hydroxyalkenals by converting redox-active metal ions into their reduced forms that promote the rapid fragmentation of hydroperoxy endoperoxides

Fragmentation of β-Hydroxy Hydroperoxides

A β-hydroxy hydroperoxide was obtained through base-catalyzed disproportionation of a hydroperoxy endoperoxide available by singlet oxygenation of cyclohepta-1,4-diene. Vitamins E and C induce fragmentation of this β-hydroxy hydroperoxide generating aldehydes, especially in the presence of redox active metal ions such as those present in vivo, e.g., under conditions of “iron overload”. This chemistry may contribute to the oxidative cleavage of polyunsaturated fatty acyls that produces similar aldehydes, which damage proteins and DNA through covalent adduction resulting in “oxidative injury”

Asymmetric Michael Addition of Substituted Rhodanines to α,β-Unsaturated Ketones Catalyzed by Bulky Primary Amines

A bulky group was introduced by design into a diamine catalyst, and a series of robust and tunable bulky chiral primary amine catalysts were developed and successfully applied in the direct conjugate addition of substituted rhodanines to α,β-unsaturated ketones. High yields (up to 99%) and excellent diastereoselectivities (up to 99:1 dr) and enantioselectivities (up to 98% ee) were observed

Asymmetric Michael Addition of Substituted Rhodanines to α,β-Unsaturated Ketones Catalyzed by Bulky Primary Amines

A bulky group was introduced by design into a diamine catalyst, and a series of robust and tunable bulky chiral primary amine catalysts were developed and successfully applied in the direct conjugate addition of substituted rhodanines to α,β-unsaturated ketones. High yields (up to 99%) and excellent diastereoselectivities (up to 99:1 dr) and enantioselectivities (up to 98% ee) were observed

xxldxlSTR

the STR frequency data for XXL and DX

Asymmetric Michael Addition of Substituted Rhodanines to α,β-Unsaturated Ketones Catalyzed by Bulky Primary Amines

A bulky group was introduced by design into a diamine catalyst, and a series of robust and tunable bulky chiral primary amine catalysts were developed and successfully applied in the direct conjugate addition of substituted rhodanines to α,β-unsaturated ketones. High yields (up to 99%) and excellent diastereoselectivities (up to 99:1 dr) and enantioselectivities (up to 98% ee) were observed

xxl_dxl_mit

haplotype sequences for XXL and DXL mountain

Asymmetric Michael Addition of Substituted Rhodanines to α,β-Unsaturated Ketones Catalyzed by Bulky Primary Amines

A bulky group was introduced by design into a diamine catalyst, and a series of robust and tunable bulky chiral primary amine catalysts were developed and successfully applied in the direct conjugate addition of substituted rhodanines to α,β-unsaturated ketones. High yields (up to 99%) and excellent diastereoselectivities (up to 99:1 dr) and enantioselectivities (up to 98% ee) were observed

A General, Scalable, Organocatalytic Nitro-Michael Addition to Enones: Enantioselective Access to All-Carbon Quaternary Stereocenters

A <i>tert</i>-leucine-derived chiral diamine catalyzes the asymmetric Michael addition of nitromethane to five-, six-, and seven-membered β-substituted cyclic enones with excellent enantioselectivity, offering scalable, asymmetric access to all-carbon quaternary stereocenters. The reaction scope can be expanded to include linear acyclic enones, and excellent levels of enantioselectivity are also observed. Furthermore, this organocatalytic, asymmetric nitro-Michael reaction is amenable to multigram scale-up and applications in the construction of an eudesmane sesquiterpenoid skeleton

Organocatalytic Enantioselective Formal [4 + 2] Cycloaddition of Enones with Cyclic <i>N</i>‑Sulfonylimines and Methylene Chromene for Chiral Spirocyclic Compounds

A highly enantioselective synthesis of spirocycles and bridged rings has been developed through a formal [4 + 2] cycloaddition reaction between enones and <i>N</i>-sulfonylimines. The unprecedented strategy has been realized utilizing <i>N</i>-sulfonylimine as a novel dienophile through enamine–iminium tautomerism of <i>N</i>-sulfonylimine. In addition, a γ,ε-regioselective cycloaddition reaction proceeded by employing methylene chromene species as dienophiles