Glucopyranosylidene-spiro-benzo[b][1,4]oxazinones and -benzo[b][1,4]thiazinones: Synthesis and investigation of their effects on glycogen phosphorylase and plant growth inhibition

Glucopyranosylidene-spiro-benzo[b][1,4]oxazinones were obtained via the corresponding 2-nitrophenyl glycosides obtained by two methods: a) AgOTf promoted glycosylation of 2-nitrophenol derivatives by O-perbenzoylated methyl (α-D-gluculopyranosylbromide)heptonate or b) Mitsunobu-type reactions of O-perbenzoylated methyl (α-D-gluculopyranose)heptonate with bulky 2-nitrophenols in the presence of DEAD and PPh3. Catalytic hydrogenation (H2-Pd/C) or partial reduction (e. g. H2-Pd/C, pyridine) of the 2-nitro groups led to spiro-benzo[b][1,4]oxazinones and spiro-benzo[b][1,4]-4-hydroxy-oxazinones by spontaneous ring closure of the intermediate 2-aminophenyl or 2-hydroxylamino glycosides, respectively. The analogous 2-aminophenyl thioglycosides, prepared by reactions of O-perbenzoylated methyl (α-D-gluculopyranosylbromide)heptonate with 2-amino-thiophenols, were cyclised in m-xylene at reflux temperature to the corresponding spiro-benzo[b][1,4]thiazinones. O-Debenzoylation was effected by Zemplen transesterificat...