2823-44-1Relevant articles and documents
A Substituent-Directed Strategy for the Selective Synthesis of L-Hexoses: An Expeditious Route to L-Idose
See, Nicholas W.,Wimmer, Norbert,Krenske, Elizabeth H.,Ferro, Vito
, p. 1575 - 1584 (2021/03/03)
L-Hexoses are rare but biologically significant components of various important biomolecules. However, most are prohibitively expensive (if commercially available) which limits their study and biotechnological exploitation. New, efficient methods to access L-hexoses and their derivatives are thus of great interest. In a previous study, we showcased a stereoselective Bu3SnH-mediated transformation of a 5-C-bromo-D-glucuronide to an L-iduronide. We have now drawn inspiration from this result to derive a new methodology – one that can be harnessed to access other L-hexoses. DFT calculations demonstrate that a combination of a β-F at the anomeric position and a methoxycarbonyl substituent at C-6 is key to optimising the selectivity for the L-hexose product. Our investigations have also culminated in the development of the shortest known synthetic route to a derivative of L-idose from a commercially available starting material (45 % yield over 3 steps). Collectively, these results address the profound lack of understanding of how to synthesise L-hexoses in a stereoselective fashion.
Chemical glucosylation of pyridoxine
Bachmann, Thomas,Rychlik, Michael
, (2020/02/13)
The chemical synthesis of pyridoxine-5′-β-D-glucoside (5′-β-PNG) was investigated using various glucoside donors and promoters. Hereby, the combination of α4,3-O-isopropylidene pyridoxine, glucose vested with different leaving and protecting groups and the application of stoichiometric amounts of different promoters was examined with regards to the preparation of the twofold protected PNG. Best results were obtained with 2,3,4,6-tetra-O-acetyl-D-glucopyranosyl fluoride and boron trifluoride etherate (2.0 eq.) as promoter at 0 °C (59%). The deprotection was accomplished stepwise with potassium/sodium hydroxide in acetonitrile/water followed by acid hydrolysis with formic acid resulting in the chemical synthesis of 5′-β-PNG.
Open-Shell Fluorination of Alkyl Bromides: Unexpected Selectivity in a Silyl Radical-Mediated Chain Process
Lovett, Gabrielle H.,Chen, Shuming,Xue, Xiao-Song,Houk,MacMillan, David W. C.
, p. 20031 - 20036 (2019/12/27)
We disclose a novel radical strategy for the fluorination of alkyl bromides via the merger of silyl radical-mediated halogen-atom abstraction and benzophenone photosensitization. Selectivity for halogen-atom abstraction from alkyl bromides is observed in the presence of an electrophilic fluorinating reagent containing a weak N-F bond despite the predicted favorability for Si-F bond formation. To probe this surprising selectivity, preliminary mechanistic and computational studies were conducted, revealing that a radical chain mechanism is operative in which kinetic selectivity for Si-Br abstraction dominates due to a combination of polar effects and halogen-atom polarizability in the transition state. This transition-metal-free fluorination protocol tolerates a broad range of functional groups, including alcohols, ketones, and aldehydes, which demonstrates the complementary nature of this strategy to existing fluorination technologies. This system has been extended to the generation of gem-difluorinated motifs which are commonly found in medicinal agents and agrochemicals.
