The reaction of pyranoside 2-uloses with DAST revised. Synthesis of 1-fluoro-ketofuranosyl fluorides and their reactivity with alcohols

Identification of bitter modulating maillard-catechin reaction products

The influence of thermally induced reaction products of a known dietary bitter compound, catechin, on bitterness perception was investigated. Catechin was reacted in low-moisture simple Maillard models (200 °C for 15 min) consisting of glycine and a reducing sugar (D-glucose, D-xylose, or D-galactose). Based on liquid chromatrography-mass spectrometry (LC-MS) isotopic labeling techniques, eight reaction products were identified and subsequently structurally elucidated by tandem LC-MS/MS and two-dimensional NMR analysis; six were report to be flavan-3-ol-spiro-C-glycosides reaction products. One of the spiro products was reported to significantly suppress the perceived bitterness intensity of a caffeine solution. Additionally, this specific spiro product was further identified in cocoa and reported to increase in concentration during bean roasting.

Highly-functionalised difluorinated cyclohexane polyols via the Diels–Alder reaction: regiochemical control via the phenylsulfonyl group

A difluorinated dienophile underwent cycloaddition reactions with a range of furans to afford cycloadducts which could be processed regio- and stereoselectively via episulfonium ions, generated by the reaction between their alkenyl groups and phenylsulfenyl chloride. The oxabicyclic products were oxidised to the phenylsulfonyl level and ring opened via E1(C)B or reductive desulfonative pathways to afford, ultimately, difluorinated cyclohexene or cyclohexane polyols.

A Potentially Divergent and Rapid Route to Analogues of Deoxycyclitols, Pentopyranoses, 6-Deoxyhexoses, and Hexoses

Direct precursors to analogues of pentopyranoses, 6-deoxyhexoses, and hexoses, in which a CF(2) center replaces the pyranose oxygen, have been synthesized rapidly from trifluoroethanol. A simple scaleable allylation reaction delivers ethers which undergo dehydrofluorination/metalation, followed by addition to either acrolein or cinnamaldehyde, to afford allylic alcohols. Fluorine-assisted [3,3]-rearrangement followed by reduction with sodium borohydride delivers diols, which undergo RCM smoothly to afford cyclohexene diols.

Highly-functionalised difluorinated (hydroxymethyl)conduritol analogues via the Diels-Alder reactions of a difluorinated dienophile

A difluorodienophile, synthesised using a Stille coupling reaction underwent tin(iv)-catalysed cycloaddition with three furans to afford oxa[2.2.1]bicycloheptenes in good yield. Reduction of ester and carbamate carbonyl groups and diol protection as the acetonide set the stage for palladium-catalysed hydrostannylation in two cases. Treatment of the stannanes with methyllithium triggered ring-opening to afford highly-functionalised difluorinated cyclohexenols which could be deprotected to afford (hydroxymethyl)conduritol analogues.

Catalytic asymmetric synthesis of a 1-deoxy-1,1-difluoro-D-xylulose

[reaction: see text] A new route, of potential strategic importance, to a difluorosugar analogue has been developed. Key steps included a Stille coupling and a highly regio- and enantioselective dihydroxylation of a highly substituted diene. Protecting groups were chosen to enhance the reactivity of the disubstituted allylic fragment in the AD reaction and allow deprotection under orthogonal conditions.