Synthesis and Testing of 2-Deoxy-2,2-Dihaloglycosides as Mechanism-Based Inhibitors of α-Glycosidases

Abstract

The synthesis of a series of 2-deoxy-2,2-dihaloglycosyl halides as potential alpha-glycosidase inactivators has been achieved via the halogenation of protected 2-fluoroglycal precursors. Direct chlorination of per-O-acetylated 2-fluoro-d-glucal and 2-fluoromaltal followed by basic deprotection yielded the corresponding 2-chloro-2-deoxy-2-fluoroglycosyl chlorides. Reaction of the per-O-acetylated 2-fluoroglycals with acetyl hypofluorite or Selectfluor yielded the 2-deoxy-2,2-difluoroglycosyl derivatives, which were converted to their alpha-chlorides using thionyl chloride and deprotected under basic conditions. Trinitrophenyl glycosides of the 2-deoxy-2,2-difluoro mono- and disaccharides were synthesized by arylation of the hemiacetals with picryl fluoride, then deprotected with HCl in methanol. All three monosaccharide derivatives caused active site-directed, time-dependent inactivation of yeast alpha-glucosidase via the trapping of covalent glycosyl-enzyme intermediates, and kinetic parameters for inactivation by each compound were determined. Surprisingly neither of the 2-deoxy-2,2-dihalomaltosyl chlorides caused time-dependent inactivation of human pancreatic alpha-amylase, despite the fact that the trinitrophenyl 2-deoxy-2,2-difluoromaltoside functioned in that mode. The trinitrophenyl glycosides appear to be approximately 1000-fold more reactive than the corresponding chlorides in the enzyme active sites.

Synthesis of 2-deoxy-2,2-difluoro-α-maltosyl fluoride and its X-ray structure in complex with Streptomyces coelicolor GlgEI-V279S

“…2-Deoxy-2,2-difluoro- α / β -maltosyl fluorides were accessed from the peracetylated 2-fluoro-maltal 1 , 10 (Supporting Information, Scheme S-1). Subsequently, peracetylated 2,2-difluoro- α -maltosyl fluoride 2 and peracetylated 2,2-difluoro-β-maltosyl fluoride 3 .…”

“…In the structure described here, Sco GlgEI-V279S contains the general base Glu423 and yet α -MTF co-crystalized with enzyme fully intact and showed no formation of a covalent glycosyl-enzyme intermediate. Based on previously reported studies involving homologous 2-deoxy-2,2-difluoroglycosides 9, 10 , the lower reactivity of the trifluoride 5 can be most readily explained by reactivity differences that result from the lower leaving group ability of the C1′ fluorine. Analysis of the X-ray complex and comparison with the complementary MCP probe reveals the hydrogen bonding interactions present within the inhibitor-enzyme complex just prior to formation of the glycosyl enzyme intermediate.…”

“…We also outline a synthesis of α -MTF ( 5 ) which was accessed from peracetylated 2,2-difluoro- α -maltosyl fluoride 2 . These targets were accessed in a single step, via the use of Selectfluor® on peracetylated 2-fluoro-maltal 1 10 .…”

Structure-activity relationships of bergenin derivatives effect on α-glucosidase inhibition

“…In previous studies, human pancreatic α-amylase has been widely known as family 13 of the glycoside hydrolases (GH13), which gathers a large variety of enzymes with varying substrate and product specificities as reflected by the 26 different EC numbers found in this family of enzymes: glycoside hydrolases (EC 3.2.1.X, the most abundant), glycoside transferases (EC 2.4.1.X) and even isomerases (EC 5.4 15,18 . Because of its ready availability and ease of handling, baker's yeast α-glucosidase (EC 3.2.1.20; GH13 family) has been widely used for enzymatic assays to find novel α-glucosidase inhibitors with different biological activities [19][20][21][22][23][24] . Bergenia ligulata (Wall.)…”

Base-catalyzed diastereoselective trimerization of trifluoroacetone

“…14 Of these compounds, fluorinated sugars represent only a small fraction – likely a consequence of the difficulty inherent in synthesizing them stereoselectively. 15–19 Nevertheless, a host of biologically relevant molecules including antivirals, antineoplastics, glycosyltransferase probes, 20 and glycosidase inhibitors, 21,22 containing fluorinated sugars have been developed, Figure 1.…”