Difluoro sugars, 2-deoxy-2,2-, synthesis

Korytnyk and coworkers have shown that reactions of xenon difluoride with acetylated glycals in the presence of boron trifluoride are a convenient route for the synthesis of 1,2-difluoro sugars, while the addition of fluorine to the double bond occurred predominantly from the less hindered side and cis adducts were mainly formed75, 76. Stereoselective transformation of tri-O-acetyl-D-galactal with xenon difluoride at -20 to +5 °C, without a catalyst in CFC13, after hydrolysis, afforded 2-deoxy-2-fluoro-D-galactose in 63% yield77. 

Zhang, X. Xia, H. Dong, X. Jin, J. Meng, W.-D. Qing, F.-L. 3-Deoxy-3,3-difluoro-D-arabi-nofuranose first stereoselective synthesis and application in the preparation of gem-difluon-nated sugar nucleosides. J. Org. Chem. 2003, 68, 9026-9033. 

Dihydroxylation of 19 with OSO4/NMO occurred without discrimination between the alkene faces to afford the fluoro sugars ( )-20 and ( )-21 as a 1 1 mixture of separable cis and trans isomers. Synthesis of the 4,4-difluoro-4-deoxy-13-DL-ribo-pyranside derivatives ( )-23e-f and 4,4-difluoro-4-deoxy-13-DL-lyxo-pyranside derivatives ( )-24e-f were realized via transacetalisation of the difluoro homoallylic alcohols 17e-f followed by RCM and dihydroxylation, respectively. 

Fluorination using DAST was employed in the synthesis of the 2 -deoxy-2 -fluoro-P-D-arabinofuranoside of 6-chloropurine (64), and a number of pyrimidine nucleosides with a 2 -deoxy-2 -fluoro-p-L-arabinofuranose unit have been prepared using base-sugar coupling procedures the thymine compound 65 (l-FMAU) had particular potency against The synthesis and antitumour activity of 2, 2 -difluoro-deoxycytidine (gemcyta-bine) has been reviewed by workers at Eli Lilly. ... 

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