作者:Mohsin O. Mohammed、Mark S. Baird、Juma'a R. Al Dulayymi、Alison Jones、Christopher D. Gwenin
DOI:10.1016/j.tet.2016.03.083
日期:2016.6
The synthesis of single mono-arabino mycolates, important lipid antigens from mycobacteria is described, using structurally defined synthetic mycolicacids. Preliminary assays indicate that these are differentially antigenic to antibodies in the serum of people with active tuberculosis.
The reaction of (diethylamino)sulfur trifluoride (DAST) with methyl 5-O-benzoyl-beta-D-xylofuranoside (1) followed by column chromatography afforded the riboside 2 (62%) and the ribo-epoxide 3 (18%) (Scheme 1). Under similar reaction conditions, the alpha-D-anomer 4 gave the riboside 5 and the difluoride 6 in 60 and 9% yield, respectively Treatment of the beta-D-xyloside 10 with DAST gave, after chromatographic purification, the riboside 11 as the principal product (48% 1 Scheme 2). These results suggest that the C(3)-O-SF2NEt2 derivatives were initially formed in the case of the xylosides studied. The distinctive feature of the reaction of DAST with the beta-D-arabinoside 12 consists in the formation of a 3- or 5-benzylideneoxoniumyl-substituted intermediate on one of the consecutive transformations, which finally give rise to the inversion of the configuration at C(3) affording the xylosides 17 (18%) and 18 (55% ): the lyxoside 14 was also isolated from the reaction mixture in a yield of 25% (Scheme 3). In the presence of the non-participating 5-O-trityl group, i.e.,from the reaction products of 21 with DAST. the compounds 23 and 23 were isolated in 16 and 52% yield, respectively (Scheme 4). It may be thus reasonable to conclude that, in the case of the beta-D-arabinosides 12 and 21, the principal route of the reaction is the formation of the intermediate C(2)-O-SF2NEt2 derivative. Unlike the alpha-D-arabinoside 26 was converted to the lyxo-epoxide 25 (53%) and the lyxoside 27 (14%), which implies the intermediate formation of the C(3)-O-SF2NEt2 derivative (Scheme 5).
One-Pot Conversion of 1,2-Diols to Epoxides: Convenient Preparation of Methyl 2,3-Anhydro-5-O-trityl-β-D-lyxofuranoside and Methyl 2,3-Anhydro-4,6-O-benzylidene-α-D-mannopyranoside
作者:V. Srinivasa Murthy、A. S. Gaitonde、S. Prahlada Rao
DOI:10.1080/00397919308009780
日期:1993.2
Tosyl chloride and sodium hydride are used to convert some 1,2-diols to epoxides in one-pot in enantiomerically/diastereomerically pure form.
A Novel Route for the Synthesis of Fluorodeoxy Sugars and Nucleosides
作者:Igor A. Mikhailopulo、Grigorii G. Sivets、Natalia B. Khripach
DOI:10.1080/15257779908041542
日期:1999.4
Ring-fluorination of alpha- and beta-D-pentofuranosides containing free secondary hydroxyl groups by (diethylamino)sulfur trifluoride (DAST) was studied.