878490-39-2Relevant academic research and scientific papers
Synthesis of a fusion-isomeric cellobionoimidazole and its evaluation against the syn-protonating glycosidase Cel7A
Mohal, Narinder,Bernet, Bruno,Vasella, Andrea
, p. 3232 - 3252 (2005)
The fusion-isomeric cellobinoimidazole 2, a potential inhibitor of the syn-protonating β-glycosidase Cel7A, was synthesised by Koenigs-Knorr glycosylation of the α-D-arabinopyranoside 32, followed by selective hydrolysis. Glycosylation of 32 with acetobromoglucose 6 proceeded with poor diastereoselectivity, giving the desired 1,3-linked β-D-disaccharide 35 as minor product, besides the major 1,3-linked α-D-disaccharide 36. Hg 2+-Promoted glycosylation of 32 led predominantly to the 1,2-ortho ester 33. Sequential removal of the silyl, acetyl, and allyl groups of 35 led to a 45:55 equilibrium mixture 2 and the manno-configured isomer 39. Similarly, deprotection of 36 gave a mixture of the maltonoimidazole 42 and the manno-configured isomer 43. According to a known protocol, the glycosyl acceptor 32 was synthesised in eleven steps and an overall yield of 8-13% from D-lyxose. The silylated arabinopyranosyl moiety of the α-D-glucosides 13-19, 33, 34, and 36 adopts a 4C1 conformation, while the arabinopyranosyl moiety of the β-D-glucosides 17 and 35 exists as a 1:3 mixture of 4C1 and 1C4 conformers, as a result of the combined preferred axial orientation of bulky vicinal substituents and the anomeric effect. MM3* Modelling evidences a preferred 4C1 conformation of 35 and 36, and stronger steric interactions between the pyranosyl moieties of 35. The equilibrium mixture 2/39 proved a poor inhibitor of Cel7A with an IC50 value of ca. 4 mM.
