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Mon, 02 Jun 2025
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Prof. Vito Ferro

The University of Queensland, Australia

Site-Selective Photobromination of Carbohydrates – Synthesis and Applications

Monday, June 02, 2025
SSB 7172 @ 3:30 p.m.

Host: Dr. David Vocadlo

 

Abstract

The Ferrier photobromination provides direct synthetic access to valuable 5-C-bromosugars.1,2 However, its broader application is constrained by the use of energy-inefficient heat lamps for irradiation and the reliance on highly toxic (and banned) CCl4 under reflux conditions. Herein, we demonstrate that the reaction proceeds rapidly and efficiently under mild conditions (≤40 °C) using benzotrifluoride (PhCF3) as a safe and environmentally benign alternative to CCl4, with irradiation by a compact photoreactor fitted with purple LEDs (405 nm), and NBS serving as the bromine source.3

Furthermore, the introduction of 2.5 mol% bromine significantly enhances substrate conversion rates and reaction efficiency. However, excessive bromine results in the formation of the glycosyl bromide, which gradually becomes the dominant product and eventually the sole product as bromine equivalents increase. We have thus optimized this latter pathway for the efficient photochemical synthesis of glycosyl bromides. The reaction proceeds via the in situ generation of HBr from bromine and PhCF3 under light irradiation, followed by substrate bromination to form glycosyl bromide in accordance with the classical bromination pathway. This strategy demonstrates excellent substrate generality for the synthesis of both 5-C-bromo sugars and glycosyl bromides, depending on the conditions. Notably, this strategy is compatible with continuous production via the use of a continuous-flow photoreactor. We also show that glycosyl bromides can be photochemically converted into either anhydroalditols, 2-deoxy sugars or C-glycosides depending on the conditions, without the use of expensive photoredox catalysts.                                   

References:

1. Ferrier, R. J.; Furneaux, R. H. J. Chem. Soc., Perkin Trans. 1 1977, 1993-1996.

2. Ferrier, R. J.; Furneaux, R. H. J. Chem. Soc., Perkin Trans. 1 1977, 1996-2000.

3. Zhang, G.; See, N. W.; Wimmer, N.; Godinez, M. J.; Cameron, S. A.; Furneaux, R. H.; Ferro, V. Org. Lett. 2024, 26, 5956-5960.

Biography

Vito Ferro completed his PhD at the University of Western Australia under the guidance of Bob Stick in 1992. Following postdoctoral studies at the Carlsberg Laboratory, Denmark (with Klaus Bock and Morten Meldal) and the University of British Columbia (with Steve Withers) he returned to Australia in 1996 to join Progen Pharmaceuticals where he spent 12 years in various positions, including Director of Drug Discovery. Following a brief period at QUT in the CRC for Polymers he moved to the University of Queensland in 2010 where he is a Professor and Biomolecular and Medicinal Chemistry Theme Leader in the School of Chemistry and Molecular Biosciences. His research interests are in carbohydrate and medicinal chemistry, with a focus on the synthesis of compounds to probe and/or inhibit carbohydrate-protein interactions involved in disease processes. Of particular interest is heparan sulfate (HS) and the development of HS mimetics as potential drugs for cancer, infectious diseases and lysosomal storage disorders.

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