Ganesh Pandey

Visible Light Photoredox Catalysis: Generation and Addition of N-Aryltetrahydroisoquinoline-Derived α-Amino Radicals to Michael Acceptors

The photoredox-catalyzed coupling of N-aryltetrahydroisoquinoline and Michael acceptors was achieved using Ru(bpy)(3)Cl(2) or [Ir(ppy)(2)(dtb-bpy)]PF(6) in combination with irradiation at 455 nm generated by a blue LED, demonstrating the trapping of visible light generated α-amino radicals. While intermolecular reactions lead to products formed by a conjugate addition, in intramolecular variants further dehydrogenation occurs, leading directly to 5,6-dihydroindolo[2,1-a]tetrahydroisoquinolines, which are relevant as potential immunosuppressive agents.

A WAVELENGTH EFFECT ON UROCANIC ACID E/Z PHOTOISOMERIZATION*

Abstract E‐Urocanic acid exhibits a single, featureless, long‐wavelength absorption band with λmax˜258 nm in water. However, the quantum efficiency for E→Z photoisomerization is wavelength dependent in this region, with the maximum value at the low energy edge of the band (e.g. 313 nm) and appreciably lower efficiencies measured at ≦ 300 nm.

Use of Enantiomerically Pure 7-Azabicyclo[2.2.1]heptan-2-ol as a Chiral Template for the Synthesis of Aminocyclitols

Using enantiopure 7-azabicyclo[2.2.1]heptane-2-ol, the synthesis of cis- as well as trans-2-aminocyclohexanols, dihydroconduramine E-1, and ent-conduramine F-1 has been described.

Suzuki Cross-Coupling/Reductive Debenzyloxycarbonylation Sequence for the Syntheses of [c]Annulated Isoquinolines: Application for the Syntheses of Pancratistatin-like Isoquinolines

A two-step strategy involving Suzuki cross-coupling of boronic acids with a diverse array of alpha-iodoenones followed by hydrogenation is developed for the construction of [c]annulated isoquinolines. This mild and efficient procedure is also applied to the synthesis of highly oxygenated isoquinolines.

A new access to polyhydroxy piperidines of the azasugar class: synthesis and glycosidase inhibition studies

A new synthetic strategy has been devised to access a variety of polyhydroxylated piperidines belonging to the azasugar class of glycosidase inhibitors. The key precursor (3aR, 7aR)-5-benzyl-2,2-dimethyl-7-methylenehexahydro[1,3]dioxo[4,5-c]pyridine is obtained by photoinduced electron transfer (PET) cyclization of the corresponding alpha-trimethylsilylmethylamine radical cation to the tethered acetylene functionality. The new molecules have been evaluated for inhibitory properties for certain beta-glycosidases and have been found to be moderate to weak inhibitors of the enzymes under study.

Direct carbon-carbon bond formation strategy at α-position of tertiary amines by photoinduced electron transfer (PET) processes

Abstract Selectivity in PET reactions based on the differences in free energy (Δ G et values for radical ion formation between amines ( 4–7 ) and alllyltrimethylsilane ( 2 ) is utelized for direct allylation at α -position of 4–7 by insitu tapping of iminium cation by 2 .

Ag(I)F as one electron oxidant for promoting sequential double desilylation : An ideal approach to non-stabilized azomethine ylides for the rapid construction of 1-azabicyclo (m:3:0) alkanes

A novel methodology for effecting sequential double desilylation by Ag(I)F for the generation of non-stabilized azomethine ylide and its application for the synthesis of 1-azabicyclo(m.3.0) alkane systems are described.

A general strategy towards the synthesis of 1-N-iminosugar type glycosidase inhibitors: demonstration by the synthesis of D- as well as L-glucose type iminosugars (isofagomines)

Both enantiomers of isofagomine, the potent glycosidase inhibitor of a type 1-N-iminosugar have been synthesized by the intramolecular cyclization of the PET generated α-trimethylsilylmethylamine radical cation with the appropriate tethered acetylene moiety.

Stereoselectivity in the cyclisation of photoinduced electron transfer (PET) generated cyclic α-amino radicals : first general stereoselective entry to 1-azabicyclo (m:n:o) alkane systems

Abstract Stereoselectivity in the intramolecular cyclisation of PET-generated cyclic α-amino radicals and its application to the synthesis of 1-azabicyclo (m:n:o) alkane systems is reported.

Iminium ion cascade reaction in the total synthesis of (+)-vincadifformine.

An iminium ion triggered cascade reaction is described in the total synthesis of (+)-vincadifformine by the coupling of 3,3-substituted tetrahydropyridine and indole derivative. The strategy allows simultaneous construction of two new rings, three new sigma bonds, and two new stereogenic centers in one pot with complete stereochemical control.