Synthesis of certain nucleoside methylenediphosphonate sugars as potential inhibitors of glycosyltransferases.

The synthesis of alpha-D-glucopyranosyl 1-(methylenediphosphonate) (11), alpha-D-galactopyranosyl 1-(methylenediphosphonate) (14), and alpha-D-mannopyranosyl 1-(methylenediphosphonate) (17) has been accomplished. [(Di-phenoxyphosphinyl)methyl]phosphonic acid (diphenyl-MDP) (5), synthesized by two different procedures, was fused with beta-D-glucopyranose pentaacetate followed by catalytic hydrogenation to give 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl methylenediphosphonate (glucose-MDP) (10). The anomeric configuration of 10 was assigned on the basis of NMR spectral studies. Condensation of 10 with 2',3'-di-O-acetyladenosine was accomplished by using 1-(mesitylene-2-sulfonyl)-3-nitro-1,2,4-triazole (MSNT) as coupling agent, and removal of the blocking groups gave adenosine 5'-[(alpha-D-glucopyranosylhydroxyphosphinyl)methyl]phosphonate (20). Uridine 5'-[(alpha-D-galactopyranosylhydroxyphosphinyl)methyl] phosphonate (23) and guanosine 5'-[(alpha-D-mannopyranosylhydroxyphosphinyl)methyl]phosphonate (26) were similarly prepared. Using a specific glycoprotein galactosyltransferase (EC 2.4.1.38) assay, uridine 5'-[(alpha-D-galactopyranosylhydroxyphosphinyl)methyl]phosphonate (23) demonstrated competitive inhibition with an apparent Ki of 97 microM. The adenosine analogue did not inhibit the enzyme. None of the above compounds show any in vitro antitumor or antiviral activity. Such specific inhibitors of glycosyltransferases may serve as specific probes to study various glycosyltransferases that might be involved in the process of metastasis.

Improved and large-scale synthesis of certain glycosyl cyanides. Synthesis of 2,5-anhydro-5-thio-D-allononitrile.

The first synthesis of 2,5-anhydro-5-thio-D-allononitrile starting with L-lyxose, via a trifluoromethanesulfonic ester intermediate, has been accomplished. Methods have been developed to achieve a large-scale synthesis of 3,4,5,7-tetra-O-acetyl-2,6-anhydro-D-glycero-D-talo-heptononitrile (5). An improved procedure has been developed to synthesize 2,5-anhydro-3,4,6-tri-O-benzoyl-D-gulononitrile (9). The structures of 5 and the thioamide derivative from 9, 2,5-anhydro-3,4,6-tri-O-benzoyl-D-gulonothioamide, were confirmed by X-ray crystallographic analysis.

Distinct effects of dual substitution on inductive and differentiative activities of C8-substituted guanine ribonucleosides.

The current studies compare the inductive and differentiative properties of 8-mercaptoguanosine with those of 7-methyl-8-oxoguanosine. 7-Methyl-8-oxoguanosine (7m8oGuo) is a new member of the family of C8-substituted guanine ribonucleosides, the first such biologically active compound described that differs from guanosine other than by the specific substituent at the 8 position. Like 8MGuo, 7m8oGuo stimulates proliferation selectively in B lymphocytes. However, 7m8oGuo possesses greater activity than 8MGuo as a mitogen and greater potency as an adjuvant for humoral immune responses. Thus, as a B-lymphocyte mitogen, 7m8oGuo induces quantitatively greater [3H]TdR uptake than does 8MGuo, but with the same concentration optimum. As an adjuvant for in vitro antibody responses, however, 7m8oGuo achieves the same degree of immunoenhancement as 8MGuo but at approximately 10-fold lower concentrations, that is, the dose-response profile has been shifted to the left. Moreover, whereas the mitogenic responses to 8MGuo and 7m8oGuo exhibit parallel kinetic profiles, the adjuvant activity of 7m8oGuo arises earlier and persists later than does that of 8MGuo. These results are interpreted in terms of two distinct intracellular pathways: one mediating mitogenesis and the other adjuvanticity.