Direct Synthesis of Unprotected C-Glycosides via Photoredox Activation of Glycosyl Ester

Organic Letters, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 2, 2025

Synthetic C-glycosides play a crucial role in molecular biology and medicine. With the surge of interest demand to provide efforts with sufficient feedstock, it is highly significant pursue novel methodologies access concise efficient manner. Here, we disclose an attractive strategy that diverges itself from conventional multistep reaction sequences involving manipulations protecting groups. Widely available native sugars first react 1,4-dihydropyridine acids via site-selective Mitsunobu reaction, converting them into bench-stable radical precursors. Under visible-light-enabled photoredox catalysis conditions, resulting glycosyl radicals undergo C–C bond formation reactions, yielding variety excellent stereoselectivity. Our method demonstrates good tolerance wide range functional groups has been successfully applied post-transformation drug molecules preparation C-glycosyl amino acids.

Language: Английский

Iridium Photoredox-Catalyzed Stereoselective C-Glycosylation with Tetrafluoropyridin-4-yl Thioglycosides: A Facile Synthesis of C-α/β-Glucogallins and Their Antioxidant Activity

ACS Catalysis, Journal Year: 2024, Volume and Issue: unknown, P. 17727 - 17738

Published: Nov. 18, 2024

We demonstrate an efficient, scalable, and stereoselective C-glycosylation with thioglycosides possessing a unique photoactive tetrafluoropyridin-4-yl (TFPy) thio radical leaving group, affording editable medicinally biologically essential C-α-glucogallin derivatives. In the presence of silyl enol ether acceptors, desulfurative coupling reaction performs smoothly under mild conditions upon exposure to blue light irradiation. This versatile protocol permits synthesis sugar-drug chimeras by C1 ketonylation complex drug-derived ethers. The scale-up synthesis, anomeric epimerization, post-C-glycosylation modification ketone sugars showcase reaction's potential utilities. Furthermore, could be applied direct carbohydrate skeleton editing equipping group on nonanomeric position. is viable for unprotected TFPy thioglycoside, route ketonyl sugars. concise six-step assembly both configurated C-glucogallins from commercially cheap glucose pentaacetate their antioxidant reactivity investigations underline promising medicinal relevance our current protocols. mechanism was investigated through trapping experiment, oxocarbenium fluorescence quenching Stern–Volmer analysis, confirming that major glycosyl intermediates are generated thioglycoside donors, whose effectively quench excited Ir(ppy)3 oxidative process, complementary product, accounting examples moderate selectivities.

Language: Английский

Visible-Light-Mediated Metal/Base-Free Stereoselective C-Alkyl Glycosylation via EDA Complexes of Glycosyl Xanthates and NHC-Borane

Organic Letters, Journal Year: 2025, Volume and Issue: unknown

Published: April 7, 2025

Owing to the toxic reagent and high temperature required, application of xanthate-based radical chemistry has been limited. To address these challenges, we report a metal- base-free, photoinduced strategy for stereoselective C-alkyl glycosylation via electron donor-acceptor (EDA) complexes glycosyl xanthates N-heterocyclic carbene (NHC)-BH3. This method generates radicals under mild conditions, affording compatibility with wide range sugars olefins produce glycosides in good excellent yields. Mechanistic studies confirmed formation EDA involvement intermediates, providing insights into reaction pathway.

Language: Английский