Stereoselective synthesis of novel thioglycosyl heterocycles

Abstract In this work, the synthesis of novel 1,2,4-triazole thioglycoside heterocycles 4 , 5 , and 8 were achieved by the reaction of 1,2,3,4,6-penta- O -acetyl- β - d -glucopyranose ( 2 ) and galactopyranose ( 3) with 4-((4-arylidene)amino)-5-methyl-1,2,4-triazole-3-thiol derivatives 1 and 6 in the presence of boron trifluoride etherate (BF 3 ·Et 2 O) as a promoter under nitrogen in CH 2 Cl 2 . Exclusive β -stereoselectivity of the formed glycosidic bond was confirmed by X-ray analysis of 4 as well as its spectral data. Different stereoselectivities were observed when the acceptor 9 , having an ortho phenolic OH group, was coupled with the donors 2 or 3 , under the same reaction conditions. Similarly, treatment of a mixture of 1- O -acetyl-2,3,5-tri- O -benzoyl- β - d -ribofuranose ( 16 ) and the thiol acceptors 1 and 15 afforded the β -thioribofuranosides 17 and 18 , respectively. The β -stereoselectivity of the reaction was confirmed by 1 H, 13 C, 1 H 1 H 2D, and 1 H 13 C 2D NMR spectral analysis.